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Warren, Warren S.

Overview:

Our work focuses on the design and application of what might best be called novel pulsed techniques, using controlled radiation fields to alter dynamics. The heart of the work is chemical physics, and most of what we do is ultrafast laser spectroscopy or nuclear magnetic resonance. It generally involves an intimate mixture of theory and experiment: recent publications are roughly an equal mix of pencil- and-paper theory, computer calculations with our workstations, and experiments. Collaborations also play an important role, particularly for medical applications.

Positions:

James B. Duke Professor of Chemistry

Chemistry
Trinity College of Arts & Sciences

Professor of Chemistry

Chemistry
Trinity College of Arts & Sciences

Professor of Physics

Physics
Trinity College of Arts & Sciences

Member of the Duke Cancer Institute

Duke Cancer Institute
School of Medicine

Chair in the Department of Physics

Physics
Trinity College of Arts & Sciences

Education:

M.S. 1979

M.S. — University of California at Berkeley

Ph.D. 1980

Ph.D. — University of California at Berkeley

News:

Grants:

OP: Collaborative Research: Multimodal Molecular Spectroscopy and Imaging in Biological Tissue and Historical Artwork

Administered By
Chemistry
AwardedBy
National Science Foundation
Role
Co-Principal Investigator
Start Date
September 01, 2016
End Date
August 31, 2019

Training in Medical Imaging

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Mentor
Start Date
July 15, 2003
End Date
August 31, 2019

Improving Melanoma Diagnosis with Pump-Probe Optical Imaging

Administered By
Chemistry
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
January 02, 2013
End Date
December 31, 2017

Coupling the Dynamics of Molecules and Spins in Nuclear Magnetic Resonance for Imaging and Oil Borehole Applications

Administered By
Mechanical Engineering and Materials Science
AwardedBy
American Chemical Society
Role
Co-Principal Investigator
Start Date
September 01, 2015
End Date
August 31, 2017

Collaborative Research: Development of Novel Nonlinear Optical Contrast for Artwork Imaging

Administered By
Chemistry
AwardedBy
National Science Foundation
Role
Co-Principal Investigator
Start Date
September 01, 2013
End Date
August 31, 2017

CMBI & NCMA Art Imaging Initiative

Administered By
Chemistry
AwardedBy
North Carolina Museum of Art
Role
Principal Investigator
Start Date
July 01, 2013
End Date
June 30, 2017

Multi-modality optical molecular imaging for melanoma tumor margin assessment

Administered By
Chemistry
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
March 01, 2014
End Date
February 28, 2017

Novel molecular contrast mechanisms for biomedical applications using pump-probe nonlinear phase dispersion spectroscopy

Administered By
Chemistry
AwardedBy
Burroughs Wellcome Fund
Role
Principal Investigator
Start Date
September 01, 2013
End Date
August 31, 2016

Sensitive and Specific Molecular Imaging of Pulmonary Nodules

Administered By
Radiology
AwardedBy
National Institutes of Health
Role
Co Investigator
Start Date
April 01, 2010
End Date
January 31, 2016

Novel Techniques in Nonlinear Optical Microscopy for Improving Melanoma Diagnosis

Administered By
Chemistry
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
April 03, 2013
End Date
August 10, 2015

Intermolecular Multiple-Quantum Coherence Effects in MRI

Administered By
Chemistry
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
December 01, 2005
End Date
April 30, 2015

Dynamics and Characterization of Long-Lived Hyperpolarized Molecules in Magnetic Resonance

Administered By
Chemistry
AwardedBy
National Science Foundation
Role
Principal Investigator
Start Date
February 15, 2011
End Date
January 31, 2015

Agilent Direct Drive 9.4T MRS/MRI Console

Administered By
Radiology
AwardedBy
National Institutes of Health
Role
Major User
Start Date
May 15, 2012
End Date
November 14, 2013

Novel Magnetic Resonance Approach to Detect BAT Distribution and Temperature

Administered By
Chemistry
AwardedBy
National Institutes of Health
Role
Investigator
Start Date
September 20, 2010
End Date
August 31, 2012

Imaging Nonlinear Absorption of Biomarkers for Improved Detection of Melanoma

Administered By
Chemistry
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
September 30, 2009
End Date
March 29, 2012
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Awards:

Fellow. International Society for Optics and Photonics.

Type
National
Awarded By
International Society for Optics and Photonics
Date
January 01, 2013

Herbert P. Broida Prize. American Physical Society.

Type
National
Awarded By
American Physical Society
Date
January 01, 2011

Publications:

Multi-spin echo spatial encoding provides three-fold improvement of temperature precision during intermolecular zero quantum thermometry.

Intermolecular multiple quantum coherences (iMQCs) are a source of MR contrast with applications including temperature imaging, anisotropy mapping, and brown fat imaging. Because all applications are limited by signal-to-noise ratio (SNR), we developed a pulse sequence that detects intermolecular zero quantum coherences with improved SNR.A previously developed pulse sequence that detects iMQCs, HOMOGENIZED with off resonance transfer (HOT), was modified with a multi-spin echo spatial encoding scheme (MSE-HOT). MSE-HOT uses a series of refocusing pulses to generate a stack of images that are averaged in postprocessing for higher SNR. MSE-HOT performance was quantified by measuring its temperature accuracy and precision during hyperthermia of ex vivo red bone marrow samples.MSE-HOT yielded a three-fold improvement in temperature precision relative to previous pulse sequences. Sources of improved precision were 1) echo averaging and 2) suppression of J-coupling in the methylene protons of fat. MSE-HOT measured temperature change with an accuracy of 0.6°C.MSE-HOT improved the temperature accuracy and precision of HOT to a level that is sufficient for hyperthermia of bone marrow.

Authors
Davis, RM; Zhou, Z; Chung, H; Warren, WS
MLA Citation
Davis, RM, Zhou, Z, Chung, H, and Warren, WS. "Multi-spin echo spatial encoding provides three-fold improvement of temperature precision during intermolecular zero quantum thermometry." Magnetic resonance in medicine 75.5 (May 2016): 1958-1966.
PMID
26077531
Source
epmc
Published In
Magnetic Resonance in Medicine
Volume
75
Issue
5
Publish Date
2016
Start Page
1958
End Page
1966
DOI
10.1002/mrm.25789

Direct and cost-efficient hyperpolarization of long-lived nuclear spin states on universal (15)N2-diazirine molecular tags.

Conventional magnetic resonance (MR) faces serious sensitivity limitations which can be overcome by hyperpolarization methods, but the most common method (dynamic nuclear polarization) is complex and expensive, and applications are limited by short spin lifetimes (typically seconds) of biologically relevant molecules. We use a recently developed method, SABRE-SHEATH, to directly hyperpolarize (15)N2 magnetization and long-lived (15)N2 singlet spin order, with signal decay time constants of 5.8 and 23 minutes, respectively. We find >10,000-fold enhancements generating detectable nuclear MR signals that last for over an hour. (15)N2-diazirines represent a class of particularly promising and versatile molecular tags, and can be incorporated into a wide range of biomolecules without significantly altering molecular function.

Authors
Theis, T; Ortiz, GX; Logan, AWJ; Claytor, KE; Feng, Y; Huhn, WP; Blum, V; Malcolmson, SJ; Chekmenev, EY; Wang, Q; Warren, WS
MLA Citation
Theis, T, Ortiz, GX, Logan, AWJ, Claytor, KE, Feng, Y, Huhn, WP, Blum, V, Malcolmson, SJ, Chekmenev, EY, Wang, Q, and Warren, WS. "Direct and cost-efficient hyperpolarization of long-lived nuclear spin states on universal (15)N2-diazirine molecular tags." Science advances 2.3 (March 25, 2016): e1501438-.
Website
http://hdl.handle.net/10161/11770
PMID
27051867
Source
epmc
Published In
Science Advances
Volume
2
Issue
3
Publish Date
2016
Start Page
e1501438
DOI
10.1126/sciadv.1501438

Preface. Biometals 2014--Proceedings of the 9th International Symposium Biometals 2014 at Duke University, Durham, NC, USA.

Authors
Crumbliss, AL; Franz, KJ; Thiele, DJ
MLA Citation
Crumbliss, AL, Franz, KJ, and Thiele, DJ. "Preface. Biometals 2014--Proceedings of the 9th International Symposium Biometals 2014 at Duke University, Durham, NC, USA." Biometals : an international journal on the role of metal ions in biology, biochemistry, and medicine 28.3 (June 2015): 431-.
PMID
25929460
Source
epmc
Published In
BioMetals
Volume
28
Issue
3
Publish Date
2015
Start Page
431
DOI
10.1007/s10534-015-9854-8

Hyperpolarization of "Neat" Liquids by NMR Signal Amplification by Reversible Exchange.

We report NMR Signal Amplification by Reversible Exchange (SABRE) hyperpolarization of the rare isotopes in "neat" liquids, each composed only of an otherwise pure target compound with isotopic natural abundance (n.a.) and millimolar concentrations of dissolved catalyst. Pyridine (Py) or Py derivatives are studied at 0.4% isotopic natural abundance ¹⁵N, deuterated, ¹⁵N enriched, and in various combinations using the SABRE-SHEATH variant (microTesla magnetic fields to permit direct ¹⁵N polarization from parahydrogen via reversible binding and exchange with an Ir catalyst). We find that the dilute n.a. ¹⁵N spin bath in Py still channels spin order from parahydrogen to dilute ¹⁵N spins, without polarization losses due to the presence of ¹⁴N or ²H. We demonstrate P(15N) ≈ 1% (a gain of 2900 fold relative to thermal polarization at 9.4 T) at high substrate concentrations. This fundamental finding has a significant practical benefit for screening potentially hyperpolarizable contrast agents without labeling. The capability of screening at n.a. level of ¹⁵N is demonstrated on examples of mono- and dimethyl-substituted Py (picolines and lutidines previously identified as promising pH sensors), showing that the presence of a methyl group in the ortho position significantly decreases SABRE hyperpolarization.

Authors
Shchepin, RV; Truong, ML; Theis, T; Coffey, AM; Shi, F; Waddell, KW; Warren, WS; Goodson, BM; Chekmenev, EY
MLA Citation
Shchepin, RV, Truong, ML, Theis, T, Coffey, AM, Shi, F, Waddell, KW, Warren, WS, Goodson, BM, and Chekmenev, EY. "Hyperpolarization of "Neat" Liquids by NMR Signal Amplification by Reversible Exchange." The journal of physical chemistry letters 6.10 (May 8, 2015): 1961-1967.
PMID
26029349
Source
epmc
Published In
Journal of Physical Chemistry Letters
Volume
6
Issue
10
Publish Date
2015
Start Page
1961
End Page
1967
DOI
10.1021/acs.jpclett.5b00782

Comparing in vivo pump-probe and multiphoton fluorescence microscopy of melanoma and pigmented lesions.

We demonstrate a multimodal approach that combines a pump-probe with confocal reflectance and multiphoton autofluorescence microscopy. Pump-probe microscopy has been proven to be of great value in analyzing thin tissue sections of pigmented lesions, as it produces molecular contrast which is inaccessible by other means. However, the higher optical intensity required to overcome scattering in thick tissue leads to higher-order nonlinearities in the optical response of melanin (e.g., two-photon pump and one-photon probe) that present additional challenges for interpreting the data. We show that analysis of pigment composition in vivo must carefully account for signal terms that are nonlinear with respect to the pump and probe intensities. We find that pump-probe imaging gives useful contrast for pigmented structures over a large range of spatial scales (100 μm to 1 cm), making it a potentially useful tool for tracking the progression of pigmented lesions without the need to introduce exogenous contrast agents.

Authors
Wilson, JW; Degan, S; Gainey, CS; Mitropoulos, T; Simpson, MJ; Zhang, JY; Warren, WS
MLA Citation
Wilson, JW, Degan, S, Gainey, CS, Mitropoulos, T, Simpson, MJ, Zhang, JY, and Warren, WS. "Comparing in vivo pump-probe and multiphoton fluorescence microscopy of melanoma and pigmented lesions." Journal of biomedical optics 20.5 (May 2015): 051012-.
PMID
25415567
Source
epmc
Published In
Journal of Biomedical Optics
Volume
20
Issue
5
Publish Date
2015
Start Page
051012
DOI
10.1117/1.jbo.20.5.051012

(15)N Hyperpolarization by Reversible Exchange Using SABRE-SHEATH.

NMR signal amplification by reversible exchange (SABRE) is a NMR hyperpolarization technique that enables nuclear spin polarization enhancement of molecules via concurrent chemical exchange of a target substrate and parahydrogen (the source of spin order) on an iridium catalyst. Recently, we demonstrated that conducting SABRE in microtesla fields provided by a magnetic shield enables up to 10% (15)N-polarization (Theis, T.; et al. J. Am. Chem. Soc.2015, 137, 1404). Hyperpolarization on (15)N (and heteronuclei in general) may be advantageous because of the long-lived nature of the hyperpolarization on (15)N relative to the short-lived hyperpolarization of protons conventionally hyperpolarized by SABRE, in addition to wider chemical shift dispersion and absence of background signal. Here we show that these unprecedented polarization levels enable (15)N magnetic resonance imaging. We also present a theoretical model for the hyperpolarization transfer to heteronuclei, and detail key parameters that should be optimized for efficient (15)N-hyperpolarization. The effects of parahydrogen pressure, flow rate, sample temperature, catalyst-to-substrate ratio, relaxation time (T1), and reversible oxygen quenching are studied on a test system of (15)N-pyridine in methanol-d4. Moreover, we demonstrate the first proof-of-principle (13)C-hyperpolarization using this method. This simple hyperpolarization scheme only requires access to parahydrogen and a magnetic shield, and it provides large enough signal gains to enable one of the first (15)N images (2 × 2 mm(2) resolution). Importantly, this method enables hyperpolarization of molecular sites with NMR T1 relaxation times suitable for biomedical imaging and spectroscopy.

Authors
Truong, ML; Theis, T; Coffey, AM; Shchepin, RV; Waddell, KW; Shi, F; Goodson, BM; Warren, WS; Chekmenev, EY
MLA Citation
Truong, ML, Theis, T, Coffey, AM, Shchepin, RV, Waddell, KW, Shi, F, Goodson, BM, Warren, WS, and Chekmenev, EY. "(15)N Hyperpolarization by Reversible Exchange Using SABRE-SHEATH." The journal of physical chemistry. C, Nanomaterials and interfaces 119.16 (April 2015): 8786-8797.
PMID
25960823
Source
epmc
Published In
The Journal of Physical Chemistry C
Volume
119
Issue
16
Publish Date
2015
Start Page
8786
End Page
8797
DOI
10.1021/acs.jpcc.5b01799

Flexible digital signal processing architecture for narrowband and spread-spectrum lock-in detection in multiphoton microscopy and time-resolved spectroscopy.

The lock-in amplifier is a critical component in many different types of experiments, because of its ability to reduce spurious or environmental noise components by restricting detection to a single frequency and phase. One example application is pump-probe microscopy, a multiphoton technique that leverages excited-state dynamics for imaging contrast. With this application in mind, we present here the design and implementation of a high-speed lock-in amplifier on the field-programmable gate array (FPGA) coprocessor of a data acquisition board. The most important advantage is the inherent ability to filter signals based on more complex modulation patterns. As an example, we use the flexibility of the FPGA approach to enable a novel pump-probe detection scheme based on spread-spectrum communications techniques.

Authors
Wilson, JW; Park, JK; Warren, WS; Fischer, MC
MLA Citation
Wilson, JW, Park, JK, Warren, WS, and Fischer, MC. "Flexible digital signal processing architecture for narrowband and spread-spectrum lock-in detection in multiphoton microscopy and time-resolved spectroscopy." The Review of scientific instruments 86.3 (March 2015): 033707-.
PMID
25832238
Source
epmc
Published In
Review of Scientific Instruments
Volume
86
Issue
3
Publish Date
2015
Start Page
033707
DOI
10.1063/1.4916261

Microtesla SABRE enables 10% nitrogen-15 nuclear spin polarization.

Parahydrogen is demonstrated to efficiently transfer its nuclear spin hyperpolarization to nitrogen-15 in pyridine and nicotinamide (vitamin B(3) amide) by conducting "signal amplification by reversible exchange" (SABRE) at microtesla fields within a magnetic shield. Following transfer of the sample from the magnetic shield chamber to a conventional NMR spectrometer, the (15)N NMR signals for these molecules are enhanced by ∼30,000- and ∼20,000-fold at 9.4 T, corresponding to ∼10% and ∼7% nuclear spin polarization, respectively. This method, dubbed "SABRE in shield enables alignment transfer to heteronuclei" or "SABRE-SHEATH", promises to be a simple, cost-effective way to hyperpolarize heteronuclei. It may be particularly useful for in vivo applications because of longer hyperpolarization lifetimes, lack of background signal, and facile chemical-shift discrimination of different species.

Authors
Theis, T; Truong, ML; Coffey, AM; Shchepin, RV; Waddell, KW; Shi, F; Goodson, BM; Warren, WS; Chekmenev, EY
MLA Citation
Theis, T, Truong, ML, Coffey, AM, Shchepin, RV, Waddell, KW, Shi, F, Goodson, BM, Warren, WS, and Chekmenev, EY. "Microtesla SABRE enables 10% nitrogen-15 nuclear spin polarization." Journal of the American Chemical Society 137.4 (February 2015): 1404-1407.
PMID
25583142
Source
epmc
Published In
Journal of the American Chemical Society
Volume
137
Issue
4
Publish Date
2015
Start Page
1404
End Page
1407
DOI
10.1021/ja512242d

In vivo pump-probe microscopy of melanoma: Characterizing shifts in excited state photodynamics with respect to invasiveness

© 2015 SPIE.Pump-probe microscopy is a multiphoton technique that generates molecular contrast from absorptive pigments, such as melanin. It holds the potential to be used as a non-invasive screening tool to discern whether a given early-stage melanoma has acquired the capacity for metastasis. Here, we examined lesions in a Braf(V600E)-driven model of melanoma to assess whether loss of the tumor suppressor gene Pten in a is accompanied by a shift in pigment expression, as measured in vivo by pump-probe microscopy. The data were analyzed to determine differences in the excited-state lifetime of melanins expressed in Pten-competent and Pten-loss pigmented lesions. Loss of the tumor suppressor Pten was found to be accompanied by a statistically significant decrease in pixel-average excited state lifetime (p = 1.3e-4).

Authors
Wilson, JW; Degan, S; Gainey, CS; Deb, S; Dall, CP; Tameze-Rivas, Y; Zhang, J; Warren, WS
MLA Citation
Wilson, JW, Degan, S, Gainey, CS, Deb, S, Dall, CP, Tameze-Rivas, Y, Zhang, J, and Warren, WS. "In vivo pump-probe microscopy of melanoma: Characterizing shifts in excited state photodynamics with respect to invasiveness." January 1, 2015.
Source
scopus
Published In
Proceedings of SPIE
Volume
9329
Publish Date
2015
DOI
10.1117/12.2079886

Intermolecular zero quantum coherences enable accurate temperature imaging in red bone marrow

© 2014 Wiley Periodicals, Inc. Magn Reson Med 74:63-70, 2015. © 2014 Wiley Periodicals, Inc. © 2014 Wiley Periodicals, Inc.Purpose Red bone marrow metastases are common in breast and prostate cancer patients, but those metastases are currently incurable. Recent developments show that hyperthermia could be a successful treatment for bone metastasis, but thermometry remains difficult or inaccurate in red marrow. Method The technique evaluated in this study measures the evolution frequency of intermolecular zero quantum coherences (iZQCs) between fat and water. The iZQC evolution frequency was mapped linearly to temperature. The temperature accuracy and coherence lifetime of the iZQC method were evaluated against other thermometry methods that are based on localized spectroscopy and multiple gradient echo imaging. Results The temperature coefficient (α) was 9.8 ± 0.7 ppb/°C with the iZQC method and 2 ± 7 ppb/°C with traditional localized spectroscopy. Conclusion Because the accuracy of thermometry is limited by the reproducibility of α between samples, iZQCs provide nearly a 10-fold accuracy improvement in red marrow (0.7 ppb/°C for iZQCs versus 7 ppb/°C for localized spectroscopy.) The iZQC technique in this study will for the first time allow accurate and quantitative thermal imaging of red marrow. Magn Reson Med, 2014.

Authors
Davis, RM; Warren, WS
MLA Citation
Davis, RM, and Warren, WS. "Intermolecular zero quantum coherences enable accurate temperature imaging in red bone marrow." Magnetic Resonance in Medicine 74.1 (January 1, 2015): 63-70.
Source
scopus
Published In
Magnetic Resonance in Medicine
Volume
74
Issue
1
Publish Date
2015
Start Page
63
End Page
70
DOI
10.1002/mrm.25372

LIGHT-SABRE enables efficient in-magnet catalytic hyperpolarization.

Nuclear spin hyperpolarization overcomes the sensitivity limitations of traditional NMR and MRI, but the most general method demonstrated to date (dynamic nuclear polarization) has significant limitations in scalability, cost, and complex apparatus design. As an alternative, signal amplification by reversible exchange (SABRE) of parahydrogen on transition metal catalysts can hyperpolarize a variety of substrates, but to date this scheme has required transfer of the sample to low magnetic field or very strong RF irradiation. Here we demonstrate "Low-Irradiation Generation of High Tesla-SABRE" (LIGHT-SABRE) which works with simple pulse sequences and low power deposition; it should be usable at any magnetic field and for hyperpolarization of many different nuclei. This approach could drastically reduce the cost and complexity of producing hyperpolarized molecules.

Authors
Theis, T; Truong, M; Coffey, AM; Chekmenev, EY; Warren, WS
MLA Citation
Theis, T, Truong, M, Coffey, AM, Chekmenev, EY, and Warren, WS. "LIGHT-SABRE enables efficient in-magnet catalytic hyperpolarization." Journal of magnetic resonance (San Diego, Calif. : 1997) 248 (November 2014): 23-26.
PMID
25299767
Source
epmc
Published In
Journal of Magnetic Resonance
Volume
248
Publish Date
2014
Start Page
23
End Page
26
DOI
10.1016/j.jmr.2014.09.005

Accessing long-lived disconnected spin-1/2 eigenstates through spins > 1/2.

Pairs of chemically equivalent (or nearly equivalent) spin-1/2 nuclei have been shown to create disconnected eigenstates that are very long-lived compared with the lifetime of pure magnetization (T1). Here the classes of molecules known to have accessible long-lived states are extended to include those with chemically equivalent spin-1/2 nuclei accessed by coupling to nuclei with spin > 1/2, in this case deuterium. At first, this appears surprising because the quadrupolar interactions present in nuclei with spin > 1/2 are known to cause fast relaxation. Yet it is shown that scalar couplings between deuterium and carbon can guide population into and out of long-lived states, i.e., those immune from the dominant relaxation mechanisms. This implies that it may be practical to consider compounds with (13)C pairs directly bound to deuterium (or even (14)N) as candidates for storage of polarization. In addition, experiments show that simple deuteration of molecules with (13)C pairs at their natural abundance is sufficient for successful lifetime measurements.

Authors
Claytor, K; Theis, T; Feng, Y; Yu, J; Gooden, D; Warren, WS
MLA Citation
Claytor, K, Theis, T, Feng, Y, Yu, J, Gooden, D, and Warren, WS. "Accessing long-lived disconnected spin-1/2 eigenstates through spins > 1/2." Journal of the American Chemical Society 136.43 (October 15, 2014): 15118-15121.
PMID
25229309
Source
epmc
Published In
Journal of the American Chemical Society
Volume
136
Issue
43
Publish Date
2014
Start Page
15118
End Page
15121
DOI
10.1021/ja505792j

Long-lived polarization protected by symmetry.

In this paper we elucidate, theoretically and experimentally, molecular motifs which permit Long-Lived Polarization Protected by Symmetry (LOLIPOPS). The basic assembly principle starts from a pair of chemically equivalent nuclei supporting a long-lived singlet state and is completed by coupling to additional pairs of spins. LOLIPOPS can be created in various sizes; here we review four-spin systems, introduce a group theory analysis of six-spin systems, and explore eight-spin systems by simulation. The focus is on AA'XnX'n spin systems, where typically the A spins are (15)N or (13)C and X spins are protons. We describe the symmetry of the accessed states, we detail the pulse sequences used to access these states, we quantify the fraction of polarization that can be stored as LOLIPOPS, we elucidate how to access the protected states from A or from X polarization and we examine the behavior of these spin systems upon introduction of a small chemical shift difference.

Authors
Feng, Y; Theis, T; Wu, T-L; Claytor, K; Warren, WS
MLA Citation
Feng, Y, Theis, T, Wu, T-L, Claytor, K, and Warren, WS. "Long-lived polarization protected by symmetry." The Journal of chemical physics 141.13 (October 2014): 134307-.
PMID
25296806
Source
epmc
Published In
Journal of Chemical Physics
Volume
141
Issue
13
Publish Date
2014
Start Page
134307
DOI
10.1063/1.4896895

Femtosecond pulse train shaping improves two-photon excited fluorescence measurements.

Measurements of two-photon absorption (TPA) cross sections are greatly confounded by even very weak linear absorption, for example from hot bands. In this case, the experimental power dependence of fluorescence from amplified and mode-locked laser systems can differ drastically, even if the peak intensity is adjusted to be the same in both cases. A simple pulse train shaping method suppresses linear contributions and extracts the nonlinear absorption cross section, demonstrated here for a meso-to-meso ethyne-bridged bis[(porphinato)zinc(II)] fluorophore (DD) at 800 nm. This approach permits reliable TPA cross-section measurement, even with standard modelocked lasers under conditions identical to that used for multiphoton microscopy.

Authors
Park, JK; Fischer, MC; Susumu, K; Therien, MJ; Warren, WS
MLA Citation
Park, JK, Fischer, MC, Susumu, K, Therien, MJ, and Warren, WS. "Femtosecond pulse train shaping improves two-photon excited fluorescence measurements." Optics letters 39.19 (October 2014): 5606-5609.
PMID
25360939
Source
epmc
Published In
Optics Letters
Volume
39
Issue
19
Publish Date
2014
Start Page
5606
End Page
5609
DOI
10.1364/ol.39.005606

Femtosecond pulse shaping enables detection of optical Kerr-effect (OKE) dynamics for molecular imaging.

We apply femtosecond pulse shaping to generate optical pulse trains that directly access a material's nonlinear refractive index (n2) and can thus determine time-resolved optical Kerr-effect (OKE) dynamics. Two types of static pulse trains are discussed: The first uses two identical fields delayed in time, plus a pump field at a different wavelength. Time-resolved OKE dynamics are retrieved by monitoring the phase of the interference pattern produced by the two identical fields in the Fourier-domain (FD) as a function of pump-probe-time-delay (where the probe is one of the two identical fields). The second pulse train uses three fields with equal time delays, but with the center field phase shifted by π/2. In this pulse scheme, changes on a sample's nonlinear refractive index produce a new frequency in the FD signal, which in turn yields background-free intensity changes in the conjugate (time) domain and provides superior signal-to-noise ratios. The demonstrated sensitivity improvements enable, for the first time to our knowledge, molecular imaging based on OKE dynamics.

Authors
Robles, FE; Fischer, MC; Warren, WS
MLA Citation
Robles, FE, Fischer, MC, and Warren, WS. "Femtosecond pulse shaping enables detection of optical Kerr-effect (OKE) dynamics for molecular imaging." Optics letters 39.16 (August 2014): 4788-4791.
PMID
25121875
Source
epmc
Published In
Optics Letters
Volume
39
Issue
16
Publish Date
2014
Start Page
4788
End Page
4791
DOI
10.1364/ol.39.004788

Intermolecular zero quantum coherences enable accurate temperature imaging in red bone marrow.

Red bone marrow metastases are common in breast and prostate cancer patients, but those metastases are currently incurable. Recent developments show that hyperthermia could be a successful treatment for bone metastasis, but thermometry remains difficult or inaccurate in red marrow.The technique evaluated in this study measures the evolution frequency of intermolecular zero quantum coherences (iZQCs) between fat and water. The iZQC evolution frequency was mapped linearly to temperature. The temperature accuracy and coherence lifetime of the iZQC method were evaluated against other thermometry methods that are based on localized spectroscopy and multiple gradient echo imaging.The temperature coefficient (α) was 9.8 ± 0.7 ppb/°C with the iZQC method and 2 ± 7 ppb/°C with traditional localized spectroscopy.Because the accuracy of thermometry is limited by the reproducibility of α between samples, iZQCs provide nearly a 10-fold accuracy improvement in red marrow (0.7 ppb/°C for iZQCs versus 7 ppb/°C for localized spectroscopy.) The iZQC technique in this study will for the first time allow accurate and quantitative thermal imaging of red marrow. Magn Reson Med, 2014. © 2014 Wiley Periodicals, Inc.

Authors
Davis, RM; Warren, WS
MLA Citation
Davis, RM, and Warren, WS. "Intermolecular zero quantum coherences enable accurate temperature imaging in red bone marrow." Magnetic resonance in medicine (July 18, 2014).
PMID
25043195
Source
epmc
Published In
Magnetic Resonance in Medicine
Publish Date
2014

Correction to “Pump–Probe Microscopic Imaging of Jurassic-Aged Eumelanin”

Authors
Simpson, MJ; Glass, KE; Wilson, JW; Wilby, PR; Simon, JD; Warren, WS
MLA Citation
Simpson, MJ, Glass, KE, Wilson, JW, Wilby, PR, Simon, JD, and Warren, WS. "Correction to “Pump–Probe Microscopic Imaging of Jurassic-Aged Eumelanin”." The Journal of Physical Chemistry Letters 5.6 (March 20, 2014): 946-946.
Source
crossref
Published In
Journal of Physical Chemistry Letters
Volume
5
Issue
6
Publish Date
2014
Start Page
946
End Page
946
DOI
10.1021/jz500406n

Femtosecond pump-probe microscopy generates virtual cross-sections in historic artwork.

The layering structure of a painting contains a wealth of information about the artist's choice of materials and working methods, but currently, no 3D noninvasive method exists to replace the taking of small paint samples in the study of the stratigraphy. Here, we adapt femtosecond pump-probe imaging, previously shown in tissue, to the case of the color palette in paintings, where chromophores have much greater variety. We show that combining the contrasts of multispectral and multidelay pump-probe spectroscopy permits nondestructive 3D imaging of paintings with molecular and structural contrast, even for pigments with linear absorption spectra that are broad and relatively featureless. We show virtual cross-sectioning capabilities in mockup paintings, with pigment separation and nondestructive imaging on an intact 14th century painting (The crucifixion by Puccio Capanna). Our approach makes it possible to extract microscopic information for a broad range of applications to cultural heritage.

Authors
Villafana, TE; Brown, WP; Delaney, JK; Palmer, M; Warren, WS; Fischer, MC
MLA Citation
Villafana, TE, Brown, WP, Delaney, JK, Palmer, M, Warren, WS, and Fischer, MC. "Femtosecond pump-probe microscopy generates virtual cross-sections in historic artwork." Proceedings of the National Academy of Sciences of the United States of America 111.5 (February 2014): 1708-1713.
PMID
24449855
Source
epmc
Published In
Proceedings of the National Academy of Sciences of USA
Volume
111
Issue
5
Publish Date
2014
Start Page
1708
End Page
1713
DOI
10.1073/pnas.1317230111

Near-infrared excited state dynamics of melanins: the effects of iron content, photo-damage, chemical oxidation, and aggregate size.

Ultrafast pump-probe measurements can discriminate the two forms of melanin found in biological tissue (eumelanin and pheomelanin), which may be useful for diagnosing and grading melanoma. However, recent work has shown that bound iron content changes eumelanin's pump-probe response, making it more similar to that of pheomelanin. Here we record the pump-probe response of these melanins at a wider range of wavelengths than previous work and show that with shorter pump wavelengths the response crosses over from being dominated by ground-state bleaching to being dominated by excited-state absorption. The crossover wavelength is different for each type of melanin. In our analysis, we found that the mechanism by which iron modifies eumelanin's pump-probe response cannot be attributed to Raman resonances or differences in melanin aggregation and is more likely caused by iron acting to broaden the unit spectra of individual chromophores in the heterogeneous melanin aggregate. We analyze the dependence on optical intensity, finding that iron-loaded eumelanin undergoes irreversible changes to the pump-probe response after intense laser exposure. Simultaneously acquired fluorescence data suggest that the previously reported "activation" of eumelanin fluorescence may be caused in part by the dissociation of metal ions or the selective degradation of iron-containing melanin.

Authors
Simpson, MJ; Wilson, JW; Robles, FE; Dall, CP; Glass, K; Simon, JD; Warren, WS
MLA Citation
Simpson, MJ, Wilson, JW, Robles, FE, Dall, CP, Glass, K, Simon, JD, and Warren, WS. "Near-infrared excited state dynamics of melanins: the effects of iron content, photo-damage, chemical oxidation, and aggregate size." The journal of physical chemistry. A 118.6 (February 2014): 993-1003.
PMID
24446774
Source
epmc
Published In
The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
Volume
118
Issue
6
Publish Date
2014
Start Page
993
End Page
1003
DOI
10.1021/jp4107475

Measuring long-lived 13C2 state lifetimes at natural abundance.

Long-lived disconnected eigenstates (for example, the singlet state in a system with two nearly equivalent carbons, or the singlet-singlet state in a system with two chemically equivalent carbons and two chemically equivalent hydrogens) hold the potential to drastically extend the lifetime of hyperpolarization in molecular tracers for in vivo magnetic resonance imaging (MRI). However, a first-principles calculation of the expected lifetime (and thus selection of potential imaging agents) is made very difficult because of the large variety of relevant intra- and intermolecular relaxation mechanisms. As a result, all previous measurements relied on costly and time consuming syntheses of (13)C labeled compounds. Here we show that it is possible to determine (13)C singlet state lifetimes by detecting the naturally abundant doubly-labeled species. This approach allows for rapid and low cost screening of potential molecular biomarkers bearing long-lived states.

Authors
Claytor, K; Theis, T; Feng, Y; Warren, W
MLA Citation
Claytor, K, Theis, T, Feng, Y, and Warren, W. "Measuring long-lived 13C2 state lifetimes at natural abundance." Journal of magnetic resonance (San Diego, Calif. : 1997) 239 (February 2014): 81-86.
PMID
24457544
Source
epmc
Published In
Journal of Magnetic Resonance
Volume
239
Publish Date
2014
Start Page
81
End Page
86
DOI
10.1016/j.jmr.2013.12.009

Quantifying melanin distribution using pump-probe microscopy and a 2D morphological autocorrelation transformation for melanoma diagnosis

Pump-probe microscopy is a quantitative molecular imaging technique that yields diagnostically relevant information from endogenous pigments, like melanin, by probing their ultrafast photodynamic properties. Previously, the method was applied to image thin, pigmented, cutaneous samples at different stages of melanoma, and results have shown a correlation between melanin photodynamic behavior and malignancy. Here, we add to the diagnostic power of the method by applying principles of mathematical morphology to parameterize melanins' image structure. Along with bulk melanin chemical information, results show that this method can differentiate invasive melanomas from non-invasive and benign lesions with high sensitivity and specificity (92.3% and 97.5%, respectively, with N = 53). The mathematical method and the statistical analysis are described in detail and results from cutaneous and ocular conjuctival melanocytic lesions are presented. © 2014 SPIE.

Authors
Robles, FE; Wilson, JW; Warren, WS
MLA Citation
Robles, FE, Wilson, JW, and Warren, WS. "Quantifying melanin distribution using pump-probe microscopy and a 2D morphological autocorrelation transformation for melanoma diagnosis." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 8949 (January 1, 2014).
Source
scopus
Published In
Proceedings of SPIE
Volume
8949
Publish Date
2014
DOI
10.1117/12.2038704

Femtosecond pulse train shaping for accurate two-photon excited fluorescence measurements

We report a simple measurement method that exploits pulse train shaping to suppress linear contributions to the fluorescence, and allows for extraction of the two-photon absorption cross sections. © 2014 OSA.

Authors
Park, JK; Fischer, MC; Susumu, K; Therien, MJ; Warren, WS
MLA Citation
Park, JK, Fischer, MC, Susumu, K, Therien, MJ, and Warren, WS. "Femtosecond pulse train shaping for accurate two-photon excited fluorescence measurements." January 1, 2014.
Source
scopus
Published In
Laser Science, LS 2014
Publish Date
2014

Composite and shaped pulses for efficient and robust pumping of disconnected eigenstates in magnetic resonance.

Hyperpolarization methods, which can enhance nuclear spin signals by orders of magnitude, open up important new opportunities in magnetic resonance. However, many of these applications are limited by spin lattice relaxation, which typically destroys the hyperpolarization in seconds. Significant lifetime enhancements have been found with "disconnected eigenstates" such as the singlet state between a pair of nearly equivalent spins, or the "singlet-singlet" state involving two pairs of chemically equivalent spins; the challenge is to populate these states (for example, from thermal equilibrium magnetization or hyperpolarization) and to later recall the population into observable signal. Existing methods for populating these states are limited by either excess energy dissipation or high sensitivity to inhomogeneities. Here we overcome the limitations by extending recent work using continuous-wave irradiation to include composite and adiabatic pulse excitations. Traditional composite and adiabatic pulses fail completely in this problem because the interactions driving the transitions are fundamentally different, but the new shapes we introduce can move population between accessible and disconnected eigenstates over a wide range of radio-frequency (RF) amplitudes and offsets while depositing insignificant amounts of power.

Authors
Theis, T; Feng, Y; Wu, T; Warren, WS
MLA Citation
Theis, T, Feng, Y, Wu, T, and Warren, WS. "Composite and shaped pulses for efficient and robust pumping of disconnected eigenstates in magnetic resonance." The Journal of chemical physics 140.1 (January 2014): 014201-.
PMID
24410222
Source
epmc
Published In
Journal of Chemical Physics
Volume
140
Issue
1
Publish Date
2014
Start Page
014201
DOI
10.1063/1.4851337

Quantifying melanin spatial distribution using pump-probe microscopy and a 2-D morphological autocorrelation transformation for melanoma diagnosis.

Pump-probe microscopy is an emerging molecular imaging technique that probes the excited state dynamics properties of pigmented samples. This method has been particularly intriguing for melanoma because, unlike other methods available, it can provide nondestructive, quantitative chemical information regarding different types of melanins, with high spatial resolution. In this Letter, we present a method based on mathematical morphology to quantify melanin structure (eumelanin, pheomelanin, and total melanin content, uniquely available with pump-probe microscopy) to aid in melanoma diagnosis. The approach applies a two-dimensional autocorrelation function and utilizes statistical parameters of the corresponding autocorrelation images, specifically, the second moments and entropy, to parameterize image structure. Along with bulk melanin chemical information, we show that this method can differentiate invasive melanomas from noninvasive and benign lesions with high sensitivity and specificity (92.3% and 97.5%, respectively, with N=53). The mathematical method and the statistical analysis are described in detail and results from cutaneous and ocular conjunctival melanocytic lesions are presented.

Authors
Robles, FE; Wilson, JW; Warren, WS
MLA Citation
Robles, FE, Wilson, JW, and Warren, WS. "Quantifying melanin spatial distribution using pump-probe microscopy and a 2-D morphological autocorrelation transformation for melanoma diagnosis." J Biomed Opt 18.12 (December 2013): 120502-.
PMID
24296994
Source
pubmed
Published In
Journal of Biomedical Optics
Volume
18
Issue
12
Publish Date
2013
Start Page
120502
DOI
10.1117/1.JBO.18.12.120502

Imaging microscopic pigment chemistry in conjunctival melanocytic lesions using pump-probe laser microscopy.

To report the application of a novel imaging technique, pump-probe microscopy, to analyze patterns of pigment chemistry of conjunctival melanocytic lesion biopsies.Histopathologic specimens of eight previously excised conjunctival melanocytic lesions were analyzed with pump-probe microscopy. The technique uses a laser scanning microscope with a two-color pulsed laser source to distinguish hemoglobin, eumelanin, and pheomelanin pigment based on differences in transient excited state and ground state photodynamics. The pump-probe signatures of conjunctival melanins were compared with cutaneous melanins. The distributions of hemoglobin, eumelanin, and pheomelanin were analyzed, and pump-probe images were correlated with adjacent hematoxylin and eosin (H&E)-stained sections.The pump-probe signatures of conjunctival melanins are similar, but not identical to cutaneous melanins. In addition, there are qualitative and quantitative differences in the structure and pigment chemistry of conjunctival benign nevi, primary acquired melanosis of the conjunctiva (PAM), and conjunctival melanomas. The pump-probe images correlated well with histopathologic features observed in the adjacent H&E-stained sections, and provided a label-free means of discerning conjunctival anatomic features and pathologic benign or malignant tissue.Pump-probe laser microscopy shows promise as an adjuvant diagnostic tool in evaluation of ocular melanocytic lesions based on morphologic correlation with the histopathology results and pigment chemistry. This initial study suggests systematic differences in pigmentation patterns among conjunctival benign nevi, primary acquired melanosis, and melanomas. In addition, pump-probe microscopy has the potential for use as a noninvasive "in vivo" optical biopsy technique to aid clinical and surgical management of conjunctival melanocytic lesions.

Authors
Wilson, JW; Vajzovic, L; Robles, FE; Cummings, TJ; Mruthyunjaya, P; Warren, WS
MLA Citation
Wilson, JW, Vajzovic, L, Robles, FE, Cummings, TJ, Mruthyunjaya, P, and Warren, WS. "Imaging microscopic pigment chemistry in conjunctival melanocytic lesions using pump-probe laser microscopy." Investigative ophthalmology & visual science 54.10 (October 21, 2013): 6867-6876.
PMID
24065811
Source
epmc
Published In
Investigative Ophthalmology and Visual Science
Volume
54
Issue
10
Publish Date
2013
Start Page
6867
End Page
6876
DOI
10.1167/iovs.13-12432

Nonlinear microscopy of eumelanin and pheomelanin with subcellular resolution.

Pump-probe microscopy nondestructively differentiates eumelanin and pheomelanin and can be used to quantify melanin distributions in thin biopsy slices. Here we have extended that work for imaging eumelanin and pheomelanin distributions on a subcellular scale, allowing elucidation of characteristics of different cell types. The results show that melanin heterogeneity, previously found to be characteristic of melanomas, persists on the subcellular scale. We have also found spectral changes associated with melanin located in melanophages that could potentially differentiate invasive pigmented melanocytes from melanophages without immunohistochemical staining.

Authors
Simpson, MJ; Wilson, JW; Phipps, MA; Robles, FE; Selim, MA; Warren, WS
MLA Citation
Simpson, MJ, Wilson, JW, Phipps, MA, Robles, FE, Selim, MA, and Warren, WS. "Nonlinear microscopy of eumelanin and pheomelanin with subcellular resolution." J Invest Dermatol 133.7 (July 2013): 1822-1826.
PMID
23353985
Source
pubmed
Published In
Journal of Investigative Dermatology
Volume
133
Issue
7
Publish Date
2013
Start Page
1822
End Page
1826
DOI
10.1038/jid.2013.37

Storage of hydrogen spin polarization in long-lived 13C2 singlet order and implications for hyperpolarized magnetic resonance imaging.

Hyperpolarized magnetic resonance imaging (MRI) is a powerful technique enabling real-time monitoring of metabolites at concentration levels not accessible by standard MRI techniques. A considerable challenge this technique faces is the T1 decay of the hyperpolarization upon injection into the system under study. Here we show that A(n)A'(n)XX' spin systems such as (13)C2-1,2-diphenylacetylene ((13)C2-DPA) sustain long-lived polarization for both (13)C and (1)H spins with decay constants of almost 4.5 min at high magnetic fields of up to 16.44 T without spin-locking; the T1 of proton polarization is only 3.8 s. Therefore, storage of the proton polarization in a (13)C2-singlet state causes a 69-fold extension of the spin lifetime. Notably, this extension is demonstrated with proton-only pulse sequences, which can be readily implemented on standard clinical scanners.

Authors
Feng, Y; Theis, T; Liang, X; Wang, Q; Zhou, P; Warren, WS
MLA Citation
Feng, Y, Theis, T, Liang, X, Wang, Q, Zhou, P, and Warren, WS. "Storage of hydrogen spin polarization in long-lived 13C2 singlet order and implications for hyperpolarized magnetic resonance imaging." Journal of the American Chemical Society 135.26 (July 2013): 9632-9635.
PMID
23781874
Source
epmc
Published In
Journal of the American Chemical Society
Volume
135
Issue
26
Publish Date
2013
Start Page
9632
End Page
9635
DOI
10.1021/ja404936p

Pump-Probe Microscopic Imaging of Jurassic-Aged Eumelanin.

Melanins are biological pigments found throughout the animal kingdom that have many diverse functions. Pump-probe imaging can differentiate the two kinds of melanins found in human skin, eumelanin and pheomelanin, the distributions of which are relevant to the diagnosis of melanoma. The long-term stability of the melanin pump-probe signal is central to using this technology to analyze melanin distributions in archived tissue samples to improve diagnostic procedures. This report shows that most of the pump-probe signal from eumelanin derived from a Jurassic cephalopod is essentially identical to that of eumelanin extracted from its modern counterpart, Sepia officinalis. However, additional classes of eumelanin signals found in the fossil reveal that the pump-probe signature is sensitive to iron content, which could be a valuable tool for pathologists who cannot otherwise know the microscopic distributions of iron in melanins.

Authors
Simpson, MJ; Glass, KE; Wilson, JW; Wilby, PR; Simon, JD; Warren, WS
MLA Citation
Simpson, MJ, Glass, KE, Wilson, JW, Wilby, PR, Simon, JD, and Warren, WS. "Pump-Probe Microscopic Imaging of Jurassic-Aged Eumelanin." J Phys Chem Lett 4.11 (June 6, 2013): 1924-1927.
PMID
23847720
Source
pubmed
Published In
Journal of Physical Chemistry Letters
Volume
4
Issue
11
Publish Date
2013
Start Page
1924
End Page
1927
DOI
10.1021/jz4008036

Pump-probe nonlinear phase dispersion spectroscopy

Authors
Robles, FE; Samineni, P; Wilson, JW; Warren, WS
MLA Citation
Robles, FE, Samineni, P, Wilson, JW, and Warren, WS. "Pump-probe nonlinear phase dispersion spectroscopy." OPTICS EXPRESS 21.8 (April 22, 2013): 9353-9364.
PMID
23609646
Source
wos-lite
Published In
Optics express
Volume
21
Issue
8
Publish Date
2013
Start Page
9353
End Page
9364
DOI
10.1364/OE.21.009353

Enhanced refocusing of fat signals using optimized multipulse echo sequences.

Endogenous magnetic resonance contrast based on the localized composition of fat in vivo can provide functional information. We found that the unequal pulse timings of the Uhrig's dynamical decoupling multipulse echo sequences significantly alter the signal intensity compared to conventional, equal-spaced Carr-Purcell-Meiboom-Gill sequences. The signal increases and decreases depending on the tissue and sequence parameters, as well as on the interpulse spacings; particularly strong differences were observed in fatty tissues, which have a highly structured morphology and a wide range of chemical shifts and J-couplings. We found that the predominant mechanism for fat refocusing under multipulse echo sequences is the chemical structure, with stimulated echoes playing a pivotal role. As a result, specialized pulse sequences can be designed to optimize refocusing of the fat chemical shifts and J-couplings, where the degree of refocusing can be tailored to specific types of fats. To determine the optimal time delays, we simulated various Uhrig dynamical decoupling and Carr-Purcell-Meiboom-Gill pulse sequence timings, and these results are compared to experimental results obtained on excised and in vivo fatty tissue. Applications to intermolecular multiple quantum coherence imaging, where the improved echo refocusing translates directly into signal enhancements, are presented as well.

Authors
Stokes, AM; Feng, Y; Mitropoulos, T; Warren, WS
MLA Citation
Stokes, AM, Feng, Y, Mitropoulos, T, and Warren, WS. "Enhanced refocusing of fat signals using optimized multipulse echo sequences." Magn Reson Med 69.4 (April 2013): 1044-1055.
PMID
22627966
Source
pubmed
Published In
Magnetic Resonance in Medicine
Volume
69
Issue
4
Publish Date
2013
Start Page
1044
End Page
1055
DOI
10.1002/mrm.24340

Pump-probe nonlinear phase dispersion spectroscopy: Molecular contrast of pigmented and non-pigmented samples

Pump-probe nonlinear phase dispersion spectroscopy is a novel method that delivers molecular information of pigmented and non-pigmented samples by probing four dimensions: phase, amplitude, wavelength, and pump-probe time-delay. Its potential for molecular imaging is explored. © OSA 2013.

Authors
Robles, FE; Claytor, K; Warren, WS
MLA Citation
Robles, FE, Claytor, K, and Warren, WS. "Pump-probe nonlinear phase dispersion spectroscopy: Molecular contrast of pigmented and non-pigmented samples." Optics InfoBase Conference Papers (January 1, 2013).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2013

Enhanced refocusing of fat signals using optimized multipulse echo sequences

Endogenous magnetic resonance contrast based on the localized composition of fat in vivo can provide functional information. We found that the unequal pulse timings of the Uhrig's dynamical decoupling multipulse echo sequences significantly alter the signal intensity compared to conventional, equal-spaced Carr-Purcell-Meiboom-Gill sequences. The signal increases and decreases depending on the tissue and sequence parameters, as well as on the interpulse spacings; particularly strong differences were observed in fatty tissues, which have a highly structured morphology and a wide range of chemical shifts and J-couplings. We found that the predominant mechanism for fat refocusing under multipulse echo sequences is the chemical structure, with stimulated echoes playing a pivotal role. As a result, specialized pulse sequences can be designed to optimize refocusing of the fat chemical shifts and J-couplings, where the degree of refocusing can be tailored to specific types of fats. To determine the optimal time delays, we simulated various Uhrig dynamical decoupling and Carr-Purcell-Meiboom-Gill pulse sequence timings, and these results are compared to experimental results obtained on excised and in vivo fatty tissue. Applications to intermolecular multiple quantum coherence imaging, where the improved echo refocusing translates directly into signal enhancements, are presented as well. © 2012 Wiley Periodicals, Inc.

Authors
Stokes, AM; Feng, Y; Mitropoulos, T; Warren, WS
MLA Citation
Stokes, AM, Feng, Y, Mitropoulos, T, and Warren, WS. "Enhanced refocusing of fat signals using optimized multipulse echo sequences." Magnetic Resonance in Medicine 69.4 (2013): 1044-1055.
Source
scival
Published In
Magnetic Resonance in Medicine
Volume
69
Issue
4
Publish Date
2013
Start Page
1044
End Page
1055
DOI
10.1002/mrm.24340

Adapting phasor analysis for nonlinear pump-probe microscopy

Phasor analysis has become a powerful tool for examining signals in fluorescence life-time microscopy (FLIM), where the analysis provides a fast, robust and intuitive means of separating different fluorescent species and mixtures thereof. In this work we adapt this analysis for pump-probe microscopy, a method that provides molecular contrast of pigmented samples by probing their excited state dynamic properties. The bipolar nature of the pump-probe signals presents important differences in the resulting phasors compared to FLIM - here, we discuss these differences and describe the behavior of bipolar signals in phasor analysis. Results show that this method is indeed able to separate multiple molecular species of interests and allows facile assessment of pigment chemistry and its distribution in samples. © 2013 Copyright SPIE.

Authors
Robles, FE; Wilson, JW; Fischer, MC; Warren, WS
MLA Citation
Robles, FE, Wilson, JW, Fischer, MC, and Warren, WS. "Adapting phasor analysis for nonlinear pump-probe microscopy." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 8589 (2013).
Source
scival
Published In
Proceedings of SPIE
Volume
8589
Publish Date
2013
DOI
10.1117/12.2002600

Imaging pigment chemistry in melanocytic conjunctival lesions with pump-probe microscopy

We extend nonlinear pump-probe microscopy, recently demonstrated to image the microscopic distribution of eumelanin and pheomelanin in unstained skin biopsy sections, to the case of melanocytic conjunctival lesions. The microscopic distribution of pigmentation chemistry serves as a functional indicator of melanocyte activity. In these conjunctival specimens (benign nevi, primary acquired melanoses, and conjunctival melanoma), we have observed pump-probe spectroscopic signatures of eumelanin, pheomelanin, hemoglobin, and surgical ink, in addition to important structural features that differentiate benign from malignant lesions. We will also discuss prospects for an in vivo 'optical biopsy' to provide additional information before having to perform invasive procedures. © 2013 Copyright SPIE.

Authors
Wilson, JW; Vajzovic, L; Robles, FE; Cummings, TJ; Mruthyunjaya, P; Warren, WS
MLA Citation
Wilson, JW, Vajzovic, L, Robles, FE, Cummings, TJ, Mruthyunjaya, P, and Warren, WS. "Imaging pigment chemistry in melanocytic conjunctival lesions with pump-probe microscopy." 2013.
Source
scival
Volume
8567
Publish Date
2013
DOI
10.1117/12.2003137

Optical clearing and multiphoton imaging of paraffin-embedded specimens

New labeling, imaging, or analysis tools could provide new retrospective insights when applied to archived, paraffinembedded samples. Deep-tissue multiphoton microscopy of paraffin-embedded specimens is achieved using optical clearing with mineral oil. We tested a variety of murine tissue specimens including skin, lung, spleen, kidney, and heart, acquiring multiphoton autofluorescence and second-harmonic generation, and pump-probe images This technique introduces the capability for non-destructive 3-dimensional microscopic imaging of existing archived pathology specimens, enabling retrospective studies. © 2013 SPIE.

Authors
Wilson, JW; Degan, S; Fischer, MC; Warren, WS
MLA Citation
Wilson, JW, Degan, S, Fischer, MC, and Warren, WS. "Optical clearing and multiphoton imaging of paraffin-embedded specimens." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 8588 (2013).
Source
scival
Published In
Proceedings of SPIE
Volume
8588
Publish Date
2013
DOI
10.1117/12.2003155

Nonlinear microscopy of eumelanin and pheomelanin with subcellular resolution

Pump-probe microscopy nondestructively differentiates eumelanin and pheomelanin and can be used to quantify melanin distributions in thin biopsy slices. Here we have extended that work for imaging eumelanin and pheomelanin distributions on a subcellular scale, allowing elucidation of characteristics of different cell types. The results show that melanin heterogeneity, previously found to be characteristic of melanomas, persists on the subcellular scale. We have also found spectral changes associated with melanin located in melanophages that could potentially differentiate invasive pigmented melanocytes from melanophages without immunohistochemical staining. © 2013 The Society for Investigative Dermatology.

Authors
Simpson, MJ; Wilson, JW; Phipps, MA; Robles, FE; Selim, MA; Warren, WS
MLA Citation
Simpson, MJ, Wilson, JW, Phipps, MA, Robles, FE, Selim, MA, and Warren, WS. "Nonlinear microscopy of eumelanin and pheomelanin with subcellular resolution." Journal of Investigative Dermatology 133.7 (2013): 1822-1826.
Source
scival
Published In
Journal of Investigative Dermatology
Volume
133
Issue
7
Publish Date
2013
Start Page
1822
End Page
1826
DOI
10.1038/jid.2013.37

In Vivo Noninvasive Detection of Brown Adipose Tissue through Intermolecular Zero-Quantum MRI

The recent discovery of active Brown Adipose Tissue (BAT) in adult humans has opened new avenues for obesity research and treatment, as reduced BAT activity seem to be implicated in human energy imbalance, diabetes, and hypertension. However, clinical applications are currently limited by the lack of non-invasive tools for measuring mass and function of this tissue in humans. Here we present a new magnetic resonance imaging method based on the normally invisible intermolecular multiple-quantum coherence 1H MR signal. This method, which doesn't require special hardware modifications, can be used to overcome partial volume effect, the major limitation of MR-based approaches that are currently being investigated for the detection of BAT in humans. With this method we can exploit the characteristic cellular structure of BAT to selectively image it, even when (as in humans) it is intimately mixed with other tissues. We demonstrate and validate this method in mice using PET scans and histology. We compare this methodology with conventional 1H MR fat fraction methods. Finally, we investigate its feasibility for the detection of BAT in humans. © 2013 Branca et al.

Authors
Branca, RT; Zhang, L; Warren, WS; Auerbach, E; Khanna, A; Degan, S; Ugurbil, K; Maronpot, R
MLA Citation
Branca, RT, Zhang, L, Warren, WS, Auerbach, E, Khanna, A, Degan, S, Ugurbil, K, and Maronpot, R. "In Vivo Noninvasive Detection of Brown Adipose Tissue through Intermolecular Zero-Quantum MRI." PLoS ONE 8.9 (2013).
PMID
24040203
Source
scival
Published In
PloS one
Volume
8
Issue
9
Publish Date
2013
DOI
10.1371/journal.pone.0074206

Nonlinear cross-phase modulation microscopy using spectral shifting

Nonlinear phase contrast may be acquired by measuring spectral shifting of an ultrafast ulse due to cross phase modulation. This technique is used to obtain structural details in a pigmented cell from a melanoma biopsy. © OSA 2012.

Authors
Wilson, JW; Samineni, P; Fischer, MC; Warren, WS
MLA Citation
Wilson, JW, Samineni, P, Fischer, MC, and Warren, WS. "Nonlinear cross-phase modulation microscopy using spectral shifting." CLEO: Applications and Technology, CLEO_AT 2012 (December 1, 2012).
Source
scopus
Published In
CLEO: Applications and Technology, CLEO_AT 2012
Publish Date
2012

Homodyne near-degenerate four-wave-mixing microscopy for graphene imaging and biomedical applications

Homodyne detection of near-degenerate four-wave-mixing with a single laser pulse is used to imaging graphene in biological samples. © OSA 2012.

Authors
Li, B; Yi, C; Brown, A; Fischer, MC; Warren, WS
MLA Citation
Li, B, Yi, C, Brown, A, Fischer, MC, and Warren, WS. "Homodyne near-degenerate four-wave-mixing microscopy for graphene imaging and biomedical applications." CLEO: Science and Innovations, CLEO_SI 2012 (December 1, 2012).
Source
scopus
Published In
CLEO: Science and Innovations, CLEO_SI 2012
Publish Date
2012

Nonlinear cross-phase modulation microscopy using spectral shifting

Nonlinear phase contrast may be acquired by measuring spectral shifting of an ultrafast pulse due to cross phase modulation. This technique is used to obtain structural details in a pigmented cell from a melanoma biopsy. © OSA 2012.

Authors
Wilson, JW; Samineni, P; Fischer, MC; Warren, WS
MLA Citation
Wilson, JW, Samineni, P, Fischer, MC, and Warren, WS. "Nonlinear cross-phase modulation microscopy using spectral shifting." CLEO: Science and Innovations, CLEO_SI 2012 (December 1, 2012).
Source
scopus
Published In
CLEO: Science and Innovations, CLEO_SI 2012
Publish Date
2012

Pump-probe microscopy of pigments used in historical art

We have developed a nonlinear microscopy technique that uses sensitive modulation transfer to extract excited state dynamics with high spatial resolution. Here, we use this technique to characterize several pigments used in historical artwork. © OSA 2012.

Authors
Samineni, P; DeCruz, A; Villafana, T; Fischer, MC; Warren, WS
MLA Citation
Samineni, P, DeCruz, A, Villafana, T, Fischer, MC, and Warren, WS. "Pump-probe microscopy of pigments used in historical art." CLEO: Science and Innovations, CLEO_SI 2012 (December 1, 2012).
Source
scopus
Published In
CLEO: Science and Innovations, CLEO_SI 2012
Publish Date
2012

Nonlinear cross-phase modulation microscopy using spectral shifting

Nonlinear phase contrast may be acquired by measuring spectral shifting of an ultrafast pulse due to cross phase modulation. This technique is used to obtain structural details in a pigmented cell from a melanoma biopsy. © OSA 2012.

Authors
Wilson, JW; Samineni, P; Fischer, MC; Warren, WS
MLA Citation
Wilson, JW, Samineni, P, Fischer, MC, and Warren, WS. "Nonlinear cross-phase modulation microscopy using spectral shifting." Optics InfoBase Conference Papers (December 1, 2012).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2012

Historical pigments revealed by pump-probe microscopy

Nonlinear optical pump-probe microscopy is able to sensitively extract excited state dynamics from historical art pigments. This technique allows three-dimensional imaging and characterization of different pigments, with far reaching applications for conservation science. © OSA 2012.

Authors
Villafaña, TE; Samineni, P; Warren, WS; Fischer, MC
MLA Citation
Villafaña, TE, Samineni, P, Warren, WS, and Fischer, MC. "Historical pigments revealed by pump-probe microscopy." Laser Science, LS 2012 (December 1, 2012).
Source
scopus
Published In
Laser Science, LS 2012
Publish Date
2012

Pump-probe imaging of melanin identifies metastatic potential of melanoma

Two-color pump-probe microscopy produces chemical contrast between melanins in skin. Increased eumelanin fraction corresponds with worse melanoma prognosis. The spatial heterogeneity of the melanin fraction, both on a cellular and sub-cellular scale, also indicates malignancy. © OSA 2012.

Authors
Simpson, MJ; Wilson, JW; Robles, FE; Phipps, T; Selim, MA; Warren, WS
MLA Citation
Simpson, MJ, Wilson, JW, Robles, FE, Phipps, T, Selim, MA, and Warren, WS. "Pump-probe imaging of melanin identifies metastatic potential of melanoma." Frontiers in Optics, FIO 2012 (December 1, 2012).
Source
scopus
Published In
Frontiers in Optics, FIO 2012
Publish Date
2012

Direct optical imaging of graphene in vitro by nonlinear femtosecond laser spectral reshaping.

Nonlinear optical microscopy, based on femtosecond laser spectral reshaping, characterized and imaged graphene samples made from different methods, both on slides and in a biological environment. This technique clearly discriminates between graphene flakes with different numbers of layers and reveals the distinct nonlinear optical properties of reduced graphene oxide as compared to mechanically exfoliated or chemical vapor deposition grown graphene. The nonlinearity makes it applicable to scattering samples (such as tissue) as opposed to previous methods, such as transmission. This was demonstrated by high-resolution imaging of breast cancer cells incubated with graphene flakes.

Authors
Li, B; Cheng, Y; Liu, J; Yi, C; Brown, AS; Yuan, H; Vo-Dinh, T; Fischer, MC; Warren, WS
MLA Citation
Li, B, Cheng, Y, Liu, J, Yi, C, Brown, AS, Yuan, H, Vo-Dinh, T, Fischer, MC, and Warren, WS. "Direct optical imaging of graphene in vitro by nonlinear femtosecond laser spectral reshaping." Nano Lett 12.11 (November 14, 2012): 5936-5940.
PMID
23101475
Source
pubmed
Published In
Nano Letters
Volume
12
Issue
11
Publish Date
2012
Start Page
5936
End Page
5940
DOI
10.1021/nl303358p

Optical clearing of archive-compatible paraffin embedded tissue for multiphoton microscopy.

Standard histopathology techniques (including paraffin embedding) are incompatible with thick tissue multiphoton imaging, and standard clearing techniques on those specimens destroy some molecular information. We demonstrate multiphoton imaging in specimens prepared according to standard histopathology techniques. This permits unlabeled 3-dimensional histology on archival tissue banks, which is of great value in evaluating prognostic indicators.

Authors
Wilson, JW; Degan, S; Warren, WS; Fischer, MC
MLA Citation
Wilson, JW, Degan, S, Warren, WS, and Fischer, MC. "Optical clearing of archive-compatible paraffin embedded tissue for multiphoton microscopy." Biomed Opt Express 3.11 (November 1, 2012): 2752-2760.
PMID
23162713
Source
pubmed
Published In
Biomedical Optics Express
Volume
3
Issue
11
Publish Date
2012
Start Page
2752
End Page
2760
DOI
10.1364/BOE.3.002752

Accessing long-lived nuclear singlet states between chemically equivalent spins without breaking symmetry.

Long-lived nuclear spin states could greatly enhance the applicability of hyperpolarized nuclear magnetic resonance. Using singlet states between inequivalent spin pairs has been shown to extend the signal lifetime by more than an order of magnitude compared to the spin lattice relaxation time (T1), but they have to be prevented from evolving into other states. In the most interesting case the singlet is between chemically equivalent spins, as it can then be inherently an eigenstate. However this presents major challenges in the conversion from bulk magnetization to singlet. In the only case demonstrated so far, a reversible chemical reaction to break symmetry was required. Here we present a pulse sequence technique that interconverts between singlet spin order and bulk magnetization without breaking the symmetry of the spin system. This technique is independent of field strength and is applicable to a broad range of molecules.

Authors
Feng, Y; Davis, RM; Warren, WS
MLA Citation
Feng, Y, Davis, RM, and Warren, WS. "Accessing long-lived nuclear singlet states between chemically equivalent spins without breaking symmetry." Nat Phys 8.11 (November 2012): 831-837.
PMID
23505397
Source
pubmed
Published In
Nature Physics
Volume
8
Issue
11
Publish Date
2012
Start Page
831
End Page
837
DOI
10.1038/nphys2425

Characterization of restricted diffusion in uni- and multi-lamellar vesicles using short distance iMQCs.

Improved understanding of the entrapment, transport, and release of drugs and small molecules within vesicles is important for drug delivery. Most methods rely on contrast agents or probe molecules; here, we propose a new MRI method to detect signal from water spins with restricted diffusion. This method is based on intermolecular double quantum coherences (iDQCs), which can probe the restricted diffusion characteristics at well-defined and tunable microscopic distance scales. By using an exceedingly short (and previously inaccessible) distance, the iDQC signal arises only from restricted diffusion spins and thereby provides a mechanism to directly image vesicle entrapment, transport, and release. Using uni- and multi-lamellar liposomes and polymersomes, we show how the composition, lamellar structure, vesicle size, and concentration affects the iDQC signal between coupled water spins at very short separation distances. The iDQC signal correlates well with conventional diffusion MRI and a proposed biexponential (multicompartmental) diffusion model. Finally, the iDQC signal was used to monitor dynamic changes in the lamellar structure as temperature-sensitive liposomes released their contents. These short distance iDQCs can probe the amount and diffusion of water entrapped in vesicles, which may be useful to further understand vesicle properties in materials science and drug delivery applications.

Authors
Stokes, AM; Wilson, JW; Warren, WS
MLA Citation
Stokes, AM, Wilson, JW, and Warren, WS. "Characterization of restricted diffusion in uni- and multi-lamellar vesicles using short distance iMQCs." J Magn Reson 223 (October 2012): 31-40.
PMID
22975234
Source
pubmed
Published In
Journal of Magnetic Resonance
Volume
223
Publish Date
2012
Start Page
31
End Page
40
DOI
10.1016/j.jmr.2012.07.021

Multicontrast nonlinear optical microscopy with a compact and rapid pulse shaper.

Homodyne detection can dramatically enhance measurement sensitivity for weak signals. In nonlinear optical microscopy it can make accessible a range of novel, intrinsic, contrast like nonlinear absorption and nonlinear phase contrast. Here a compact and rapid pulse shaper is developed, implemented, and demonstrated for homodyne detection in nonlinear microscopy with high-repetition rate mode-locked femtosecond lasers. With this method we generate two-photon absorption (TPA) and self-phase modulation images of gold nanostars in biological samples. Simultaneous imaging of two-photon luminescence and TPA also enables us to produce two-photon quantum yield images.

Authors
Li, B; Claytor, KE; Yuan, H; Vo-Dinh, T; Warren, WS; Fischer, MC
MLA Citation
Li, B, Claytor, KE, Yuan, H, Vo-Dinh, T, Warren, WS, and Fischer, MC. "Multicontrast nonlinear optical microscopy with a compact and rapid pulse shaper." Opt Lett 37.13 (July 1, 2012): 2763-2765.
PMID
22743521
Source
pubmed
Published In
Optics Letters
Volume
37
Issue
13
Publish Date
2012
Start Page
2763
End Page
2765

Revisiting the mean-field picture of dipolar effects in solution NMR.

For more than three decades, the classical or mean-field picture describing the distant dipolar field has been almost always simplified to an effective field proportional to the local longitudinal magnetization, differing only by a scale factor of 1.5 for homomolecular (identical resonance frequency) and heteromolecular interactions. We re-examine the underlying assumptions, and show both theoretically and experimentally that the mathematical framework needs to be modified for modern applications such as imaging. We demonstrate new pulse sequences which produce unexpected effects; for example, modulating an arbitrarily small fraction of the magnetization can substantially alter the frequency evolution. Thus, matched gradient pulse pairs (a seemingly innocuous module in thousands of existing pulse sequences) can alter the time evolution in highly unexpected ways, particularly with small flip angle pulses such as those used in hyperpolarized experiments. We also show that specific gradient pulse combinations can retain only dipolar interactions between unlike spins, and the dipolar field can generate a secular Hamiltonian proportional to I(x).

Authors
Chen, YM; Branca, RT; Warren, WS
MLA Citation
Chen, YM, Branca, RT, and Warren, WS. "Revisiting the mean-field picture of dipolar effects in solution NMR." J Chem Phys 136.20 (May 28, 2012): 204509-.
PMID
22667573
Source
pubmed
Published In
Journal of Chemical Physics
Volume
136
Issue
20
Publish Date
2012
Start Page
204509
DOI
10.1063/1.4721637

Pump-probe imaging of historical pigments used in paintings.

A recently developed nonlinear optical pump-probe microscopy technique uses modulation transfer to sensitively extract excited-state dynamics of endogenous biological pigments, such as eumelanin and pheomelanin. In this work, we use this method to image and characterize several inorganic and organic pigments used in historical art. We show substantial differences in the near-IR pump-probe signatures from nominally similar pigments and suggest extensions to art restoration.

Authors
Samineni, P; deCruz, A; Villafaña, TE; Warren, WS; Fischer, MC
MLA Citation
Samineni, P, deCruz, A, Villafaña, TE, Warren, WS, and Fischer, MC. "Pump-probe imaging of historical pigments used in paintings." Opt Lett 37.8 (April 15, 2012): 1310-1312.
PMID
22513669
Source
pubmed
Published In
Optics Letters
Volume
37
Issue
8
Publish Date
2012
Start Page
1310
End Page
1312

Cross-phase modulation imaging.

We demonstrate a cross-phase modulation measurement technique based on the sensitive detection of modulation transfer in a pump-probe setup. By modulating the amplitude of the pump beam and spectrally analyzing the probe beam, we achieve a rapid, background-free measurement of nonlinear phase modulation using power levels acceptable in biological imaging. This measurement technique would allow the extension of widely employed phase microscopy methods to the nonlinear regime, providing intrinsic and universal nonlinear contrast for biological imaging.

Authors
Samineni, P; Li, B; Wilson, JW; Warren, WS; Fischer, MC
MLA Citation
Samineni, P, Li, B, Wilson, JW, Warren, WS, and Fischer, MC. "Cross-phase modulation imaging." Opt Lett 37.5 (March 1, 2012): 800-802.
PMID
22378398
Source
pubmed
Published In
Optics Letters
Volume
37
Issue
5
Publish Date
2012
Start Page
800
End Page
802

Melanoma classification from hidden Markov tree features

Melanoma detection relies on visual inspection of skin samples under the microscope via a qualitative set of indicators, causing large discordance among pathologists. New developments in pump-probe imaging enable the extraction of melanin intensity levels from skin samples and provide baseline qualitative figures for melanoma detection and classification. However, such basic figures do not capture the diverse types of cellular structure that distinguish different stages of melanoma. In this paper, we propose an initial approach for feature extraction for classification purposes via Hidden Markov Tree models trained on skin sample melanin intensity images. Our experimental results show that the proposed features provide a mathematical microscope that is able to better discriminate cellular structure, enabling successful classification of skin samples that are mislabeled when the baseline melanin intensity qualitative figures are used. © 2012 IEEE.

Authors
Duarte, MF; Matthews, TE; Warren, WS; Calderbank, R
MLA Citation
Duarte, MF, Matthews, TE, Warren, WS, and Calderbank, R. "Melanoma classification from hidden Markov tree features." ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings (2012): 685-688.
Source
scival
Published In
IEEE International Conference on Acoustics Speech and Signal Processing
Publish Date
2012
Start Page
685
End Page
688
DOI
10.1109/ICASSP.2012.6287976

Homodyne near-degenerate four-wave-mixing microscopy for graphene imaging and biomedical applications

Homodyne detection of near-degenerate four-wave-mixing with a single laser pulse is used to imaging graphene in biological samples. © 2012 OSA.

Authors
Li, B; Yi, C; Brown, A; Fischer, MC; Warren, WS
MLA Citation
Li, B, Yi, C, Brown, A, Fischer, MC, and Warren, WS. "Homodyne near-degenerate four-wave-mixing microscopy for graphene imaging and biomedical applications." 2012 Conference on Lasers and Electro-Optics, CLEO 2012 (2012).
Source
scival
Published In
2012 Conference on Lasers and Electro-Optics, CLEO 2012
Publish Date
2012

Phasor analysis for nonlinear pump-probe microscopy

Pump-probe microscopy provides molecular information by probing transient, excited state dynamic properties of pigmented samples. Analysis of the transient response is typically conducted using principal component analysis or multi-exponential fitting, however these methods are not always practical or feasible. Here, we show an adaptation of phasor analysis to provide an intuitive, robust, and efficient method for analyzing and displaying pump-probe images, thereby alleviating some of the challenges associated with differentiating multiple pigments. A theoretical treatment is given to understand how the complex transient signals map onto the phasor plot. Analyses of cutaneous and ocular pigmented tissue samples, as well as historical pigments in art demonstrate the utility of this approach. ©2012 Optical Society of America.

Authors
Robles, FE; Wilson, JW; Fischer, MC; Warren, WS
MLA Citation
Robles, FE, Wilson, JW, Fischer, MC, and Warren, WS. "Phasor analysis for nonlinear pump-probe microscopy." Optics Express 20.15 (2012): 17082-17092.
Source
scival
Published In
Optics express
Volume
20
Issue
15
Publish Date
2012
Start Page
17082
End Page
17092
DOI
10.1364/OE.20.017082

Cross-phase modulation spectral shifting: Nonlinear phase contrast in a pump-probe microscope

Microscopy with nonlinear phase contrast is achieved by a simple modification to a nonlinear pump-probe microscope. The technique measures cross-phase modulation by detecting a pump-induced spectral shift in the probe pulse. Images with nonlinear phase contrast are acquired both in transparent and absorptive media. In paraffin-embedded biopsy sections, cross-phase modulation complements the chemically-specific pump-probe images with structural context. © 2012 Optical Society of America.

Authors
Wilson, JW; Samineni, P; Warren, WS; Fischer, MC
MLA Citation
Wilson, JW, Samineni, P, Warren, WS, and Fischer, MC. "Cross-phase modulation spectral shifting: Nonlinear phase contrast in a pump-probe microscope." Biomedical Optics Express 3.5 (2012): 854-862.
PMID
22567580
Source
scival
Published In
Biomedical Optics Express
Volume
3
Issue
5
Publish Date
2012
Start Page
854
End Page
862
DOI
10.1364/BOE.3.000854

Nonlinear cross-phase modulation microscopy using spectral shifting

Nonlinear phase contrast may be acquired by measuring spectral shifting of an ultrafast pulse due to cross phase modulation. This technique is used to obtain structural details in a pigmented cell from a melanoma biopsy. © 2012 OSA.

Authors
Wilson, JW; Samineni, P; Fischer, MC; Warren, WS
MLA Citation
Wilson, JW, Samineni, P, Fischer, MC, and Warren, WS. "Nonlinear cross-phase modulation microscopy using spectral shifting." 2012 Conference on Lasers and Electro-Optics, CLEO 2012 (2012).
Source
scival
Published In
2012 Conference on Lasers and Electro-Optics, CLEO 2012
Publish Date
2012

Pump-probe microscopy of pigments used in historical art

We have developed a nonlinear microscopy technique that uses sensitive modulation transfer to extract excited state dynamics with high spatial resolution. Here, we use this technique to characterize several pigments used in historical artwork. © 2012 OSA.

Authors
Samineni, P; Cruz, AD; Villafana, T; Fischer, MC; Warren, WS
MLA Citation
Samineni, P, Cruz, AD, Villafana, T, Fischer, MC, and Warren, WS. "Pump-probe microscopy of pigments used in historical art." 2012 Conference on Lasers and Electro-Optics, CLEO 2012 (2012).
Source
scival
Published In
2012 Conference on Lasers and Electro-Optics, CLEO 2012
Publish Date
2012

In vivo pump-probe microscopy of melanoma and pigmented lesions

A growing number of dermatologists and pathologists are concerned that the rapidly rising incidence of melanoma reflects not a true 'epidemic' but an increasing tendency to overdiagnose pigmented lesions. Addressing this problem requires both a better understanding of early-stage melanoma and new diagnostic criteria based on more than just cellular morphology and architecture. Here we present a method for in-vivo optical microscopy that utilizes pump-probe spectroscopy to image the distribution of the two forms of melanin in skin: eumelanin and pheomelanin. Images are acquired in a scanning microscope with a sensitive modulation transfer technique by analyzing back-scattered probe light with a lock-in amplifier. Early-stage melanoma is studied in a human skin xenografted mouse model. Individual melanocytes have been observed, in addition to pigmented keratinocytes. Combining the pump-probe images simultaneously with other noninvasive laser microscopy methods (confocal reflectance, multiphoton autofluorescence, and second harmonic generation) allows visualization of the skin architecture, framing the functional pump-probe image in the context of the surrounding tissue morphology. It is found that pump-probe images of melanin can be acquired with low peak intensities, enabling wide field-of-view pigmentation surveys. Finally, we investigate the diagnostic potential of the additional chemical information available from pump-probe microscopy. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

Authors
Wilson, JW; Degan, S; Mitropoulos, T; Selim, MA; Zhang, JY; Warren, WS
MLA Citation
Wilson, JW, Degan, S, Mitropoulos, T, Selim, MA, Zhang, JY, and Warren, WS. "In vivo pump-probe microscopy of melanoma and pigmented lesions." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 8226 (2012).
Source
scival
Published In
Proceedings of SPIE
Volume
8226
Publish Date
2012
DOI
10.1117/12.908821

Detection of iron-labeled single cells by MR imaging based on intermolecular double quantum coherences at 14 T

To evaluate the efficiency and feasibility of intermolecular multiple quantum coherence (iMQC) magnetic resonance (MR) imaging for single cell detection, we obtained intermolecular double quantum coherence (iDQC) and conventional gradient echo (GE) images of macrophage cells labeled by contrast agents in gel. The iDQC images obtained with echo-planar readout visualized the labeled cells effectively and with a higher contrast than seen in conventional GE images, especially at low planar resolutions and with thick slices. This implies that iDQC imaging with contrast agents could be a good alternative to conventional MR imaging for detecting labeled single cells or cell tracking under favorable conditions. © 2012 Elsevier Inc. All rights reserved.

Authors
Cho, J-H; Hong, KS; Cho, J; Chang, S-K; Cheong, C; Lee, NH; Kim, H; Warren, WS; Ahn, S; Lee, C
MLA Citation
Cho, J-H, Hong, KS, Cho, J, Chang, S-K, Cheong, C, Lee, NH, Kim, H, Warren, WS, Ahn, S, and Lee, C. "Detection of iron-labeled single cells by MR imaging based on intermolecular double quantum coherences at 14 T." Journal of Magnetic Resonance 217 (2012): 86-91.
PMID
22436467
Source
scival
Published In
Journal of Magnetic Resonance
Volume
217
Publish Date
2012
Start Page
86
End Page
91
DOI
10.1016/j.jmr.2012.02.014

Pump-probe melanoma imaging: Applications to high-resolution and in-vivo microscopy

Pump-probe imaging of melanin with near-infrared pulses has been extended to two new domains: high-resolution imaging of the melanin content of melanosomes in an individual melanocyte and epi-detected in vivo microscopy of a developing melanoma. © OSA/ CLEO 2011.

Authors
Wilson, JW; Matthews, TE; Degan, S; Zhang, JY; Simpson, MJ; Warren, WS
MLA Citation
Wilson, JW, Matthews, TE, Degan, S, Zhang, JY, Simpson, MJ, and Warren, WS. "Pump-probe melanoma imaging: Applications to high-resolution and in-vivo microscopy." Optics InfoBase Conference Papers (December 1, 2011).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2011

Pump-probe melanoma imaging: Applications to high-resolution and in-vivo microscopy

Pump-probe imaging of melanin with near-infrared pulses has been extended to two new domains: high-resolution imaging of the melanin content of melanosomes in an individual melanocyte and epi-detected in vivo microscopy of a developing melanoma. © OSA/ CLEO 2011.

Authors
Wilson, JW; Matthews, TE; Degan, S; Zhang, JY; Simpson, MJ; Warren, WS
MLA Citation
Wilson, JW, Matthews, TE, Degan, S, Zhang, JY, Simpson, MJ, and Warren, WS. "Pump-probe melanoma imaging: Applications to high-resolution and in-vivo microscopy." Optics InfoBase Conference Papers (December 1, 2011).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2011

Pump-probe microscopy captures cellular detail of melanoma in-vivo.

Pump-probe imaging of melanin with near-infrared pulses coupled with multphoton autofluorescence captures both chemical contrast and cellular detail in a live, developing melanoma. © 2011 OSA.

Authors
Wilson, JW; Matthews, TE; Degan, S; Zhang, JY; Simpson, MJ; Warren, WS
MLA Citation
Wilson, JW, Matthews, TE, Degan, S, Zhang, JY, Simpson, MJ, and Warren, WS. "Pump-probe microscopy captures cellular detail of melanoma in-vivo." Optics InfoBase Conference Papers (December 1, 2011).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2011

Pump-probe melanoma imaging: Applications to high-resolution and in-vivo microscopy

Pump-probe imaging of melanin with near-infrared pulses has been extended to two new domains: high-resolution imaging of the melanin content of melanosomes in an individual melanocyte and epi-detected in vivo microscopy of a developing melanoma. © OSA/ CLEO 2011.

Authors
Wilson, JW; Matthews, TE; Degan, S; Zhang, JY; Simpson, MJ; Warren, WS
MLA Citation
Wilson, JW, Matthews, TE, Degan, S, Zhang, JY, Simpson, MJ, and Warren, WS. "Pump-probe melanoma imaging: Applications to high-resolution and in-vivo microscopy." Optics InfoBase Conference Papers (December 1, 2011).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2011

Optimizing shape of femtosecond laser pulses for homodyne detection of nonlinear optical signals

Based on homodyne detection of weak nonlinear signals with our spectral reshaping technique, pulse shapes are optimized for fast nonlinear imaging using femtosecond mode-locked lasers. © 2011 OSA.

Authors
Li, B; Claytor, K; Warren, WS; Fischer, MC
MLA Citation
Li, B, Claytor, K, Warren, WS, and Fischer, MC. "Optimizing shape of femtosecond laser pulses for homodyne detection of nonlinear optical signals." Optics InfoBase Conference Papers (December 1, 2011).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2011

Accessing nonlinear phase contrast in biological tissue using femtosecond laser pulse shaping

Nonlinear imaging takes advantage of the localized nature of the interaction to achieve high spatial resolution, optical sectioning, and deeper penetration in tissue. However, nonlinear contrast (other than fluorescence or harmonic generation) is generally difficult to measure because it is overwhelmed by the large background of detected illumination light. Especially challenging to measure is the nonlinear refractive index-accessing this quantity would allow the extension of widely employed phase microscopy methods to the nonlinear regime. We have developed a technique to suppress the background in these types of measurements by using femtosecond pulse shaping to encode nonlinear interactions in background-free regions of the frequency spectrum. Using this individual pulse shaping based technique we have been able to measure self-phase modulation (SPM) in highly scattering environments, such as biological tissue, with very modest power levels. Using our measurement technique we have demonstrated strong intrinsic SPM signatures of glutamate-induced neuronal activity in hippocampal brain slices. We have also extended this measurement method to cross-phase modulation, the two-color analogue to SPM. The two-color approach dramatically improves the measurement sensitivity by reducing undesired background and associated noise. We will describe the nonlinear phase contrast measurement technique and report on its application for imaging neuronal activity. © 2011 SPIE-OSA.

Authors
Fischer, MC; Samineni, P; Li, B; Claytor, K; Warren, WS
MLA Citation
Fischer, MC, Samineni, P, Li, B, Claytor, K, and Warren, WS. "Accessing nonlinear phase contrast in biological tissue using femtosecond laser pulse shaping." Optics InfoBase Conference Papers (December 1, 2011).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2011

Imaging the distribution of melanin in human skin lesions with pump-probe microscopy

Authors
Simpson, MJ; Wilson, JW; Matthews, TE; Duarte, M; Calderbank, R; Warren, WS
MLA Citation
Simpson, MJ, Wilson, JW, Matthews, TE, Duarte, M, Calderbank, R, and Warren, WS. "Imaging the distribution of melanin in human skin lesions with pump-probe microscopy." Optics InfoBase Conference Papers (December 1, 2011).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2011

Cross-phase modulation microscopy

We report our recently developed spectral re-shaping technique for cross-phase modulation imaging, which extends widely employed phase microscopy to the nonlinear regime. © 2011 OSA.

Authors
Samineni, P; Fischer, MC; Warren, WS
MLA Citation
Samineni, P, Fischer, MC, and Warren, WS. "Cross-phase modulation microscopy." Optics InfoBase Conference Papers (December 1, 2011).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2011

Femtosecond pulse shaping enables nonlinear imaging in highly scattering materials

Spectral re-shaping of pulses from a mode-locked femtosecond laser allows detection of two photon absorption and self phase modulation in highly scattering materials, which permits nonlinear tissue imaging with this intrinsic contrast. © 2011 OSA.

Authors
Claytor, K; Li, B; Samineni, P; Warren, W; Fischer, M
MLA Citation
Claytor, K, Li, B, Samineni, P, Warren, W, and Fischer, M. "Femtosecond pulse shaping enables nonlinear imaging in highly scattering materials." Optics InfoBase Conference Papers (December 1, 2011).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2011

Breasts and brains, similarities and differences: The role of nonlinear microscopy in molecular imaging

I will discuss the opportunities for nonlinear optical molecular imaging, focusing on measurement of intrinsic nonlinear optical signatures of cancer or of brain activation, and put this work in context with other modalities. © 2011 OSA.

Authors
Warren, WS
MLA Citation
Warren, WS. "Breasts and brains, similarities and differences: The role of nonlinear microscopy in molecular imaging." Optics InfoBase Conference Papers (December 1, 2011).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2011

Spectral shifting measurement of cross phase modulation with a balanced photodiode

Biomedical imaging of the nonlinear refractive index n2 requires a measurement technique that, unlike z-scan, is robust in inhomogeneous scattering media. We present an adaptation of a pump-probe experiment to measure n2 via cross-phase modulation. © 2011 OSA.

Authors
Wilson, JW; Warren, WS
MLA Citation
Wilson, JW, and Warren, WS. "Spectral shifting measurement of cross phase modulation with a balanced photodiode." Optics InfoBase Conference Papers (December 1, 2011).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2011

In vivo NMR detection of diet-induced changes in adipose tissue composition.

We introduce an in vivo spectroscopic method to assess the effects of diet on fatty acid composition of the predominant chemical constituent of adipocytes in mice. To do this, we make use of a nonlinear NMR signal that, unlike a standard NMR signal, is intrinsically insensitive to local magnetic field inhomogeneities and which naturally suppresses the large water signal from nonfatty tissues. Our method yields fat composition information from fat depots distributed over large sample volumes in a single experiment, without requiring the use of tedious shimming procedures, voxel selection, or water suppression. Our results suggest that this method can reveal clear differences in adipose tissue composition of mice fed a standard chow diet compared with mice fed a diet rich in polyunsaturated fatty acids. With further developments this method could be used to obtain information on human lipid composition noninvasively and to track changes in lipid composition induced by diet intervention, pharmaceutical drugs, and exercise.

Authors
Branca, RT; Warren, WS
MLA Citation
Branca, RT, and Warren, WS. "In vivo NMR detection of diet-induced changes in adipose tissue composition." J Lipid Res 52.4 (April 2011): 833-839.
PMID
21270099
Source
pubmed
Published In
Journal of lipid research
Volume
52
Issue
4
Publish Date
2011
Start Page
833
End Page
839
DOI
10.1194/jlr.D012468

Inhomogeneity-free heteronuclear iMQC.

Intermolecular dipolar interactions between proton and carbon spins can be used to indirectly detect carbon spectra with high sensitivity. In this communication, we present a modified sequence that, in addition to the high sensitivity of heteronuclear intermolecular multiple quantum coherence (iMQC) experiments, retains the line narrowing capability characteristic of homonuclear zero-quantum coherences. We demonstrate that this sequence can be used to obtain high resolution (13)C spectra in the presence of magnetic field inhomogeneities, both for thermal and hyperpolarized samples, and discuss applications to water-hyperpolarized carbon imaging.

Authors
Branca, RT; Jenista, ER; Warren, WS
MLA Citation
Branca, RT, Jenista, ER, and Warren, WS. "Inhomogeneity-free heteronuclear iMQC." J Magn Reson 209.2 (April 2011): 347-351.
PMID
21316278
Source
pubmed
Published In
Journal of Magnetic Resonance
Volume
209
Issue
2
Publish Date
2011
Start Page
347
End Page
351
DOI
10.1016/j.jmr.2011.01.018

Pump-probe imaging differentiates melanoma from melanocytic nevi.

Melanoma diagnosis is clinically challenging: the accuracy of visual inspection by dermatologists is highly variable and heavily weighted toward false positives. Even the current gold standard of biopsy results in varying diagnoses among pathologists. We have developed a multiphoton technique (based on pump-probe spectroscopy) that directly determines the microscopic distribution of eumelanin and pheomelanin in pigmented lesions of human skin. Our initial results showed a marked difference in the chemical variety of melanin between nonmalignant nevi and melanoma, as well as a number of substantial architectural differences. We examined slices from 42 pigmented lesions and found that melanomas had an increased eumelanin content compared to nonmalignant nevi. When used as a diagnostic criterion, the ratio of eumelanin to pheomelanin captured all investigated melanomas but excluded three-quarters of dysplastic nevi and all benign dermal nevi. Additional evaluation of architectural and cytological features revealed by multiphoton imaging, including the maturation of melanocytes, presence of pigmented melanocytes in the dermis, number and location of melanocytic nests, and confluency of pigmented cells in the epidermis, further increased specificity, allowing rejection of more than half of the remaining false-positive results. We then adapted this multiphoton imaging technique to hematoxylin and eosin (H&E)-stained slides. By adding melanin chemical contrast to H&E-stained slides, pathologists will gain complementary information to increase the ease and accuracy of melanoma diagnosis.

Authors
Matthews, TE; Piletic, IR; Selim, MA; Simpson, MJ; Warren, WS
MLA Citation
Matthews, TE, Piletic, IR, Selim, MA, Simpson, MJ, and Warren, WS. "Pump-probe imaging differentiates melanoma from melanocytic nevi." Sci Transl Med 3.71 (February 23, 2011): 71ra15-.
PMID
21346168
Source
pubmed
Published In
Science Translational Medicine
Volume
3
Issue
71
Publish Date
2011
Start Page
71ra15
DOI
10.1126/scitranslmed.3001604

In vivo brown adipose tissue detection and characterization using water-lipid intermolecular zero-quantum coherences.

Brown adipose tissue and white adipose tissue depots are noninvasively characterized in vitro and in vivo in healthy and obese mice using intermolecular zero-quantum coherence transitions between lipid and water spins. Intermolecular zero-quantum coherences enable selective detection of spatial correlation between water and lipid spins and thereby the hydration of fatty deposits with subvoxel resolution. At about a 100 mm distance scale, the major observed peaks are between water, methylene protons at 1.3 ppm, and olefinic protons at 5.3 ppm. Our in vitro results show that the methylene-olefinic intermolecular zero-quantum coherence signal is strong both in brown and white adipose tissues, but that the water-methylene intermolecular zero-quantum coherence signal is characteristic only of brown adipose tissue. In vivo, the ratio of these peaks is substantially higher in lean or young mice than in old or obese mice.

Authors
Branca, RT; Warren, WS
MLA Citation
Branca, RT, and Warren, WS. "In vivo brown adipose tissue detection and characterization using water-lipid intermolecular zero-quantum coherences." Magn Reson Med 65.2 (February 2011): 313-319.
PMID
20939093
Source
pubmed
Published In
Magnetic Resonance in Medicine
Volume
65
Issue
2
Publish Date
2011
Start Page
313
End Page
319
DOI
10.1002/mrm.22622

Nonlinear phase contrast imaging in neuronal tissue

We demonstrate nonlinear phase contrast imaging in highly scattering media using rapid femtosecond pulse shaping of mode-locked laser pulses. We will also discuss potential applications of this technique for intrinsic functional neuronal imaging. © 2011 OSA: BODA/NTM/OMP/OTA.

Authors
Samineni, P; Fischer, MC; Liu, HC; Yasuda, R; Warren, WS
MLA Citation
Samineni, P, Fischer, MC, Liu, HC, Yasuda, R, and Warren, WS. "Nonlinear phase contrast imaging in neuronal tissue." January 1, 2011.
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2011

Beyond Pathology: Pump-probe imaging of skin slices provides additional indicators of melanoma

Principal component analysis of images taken with a pump-probe scanning microscope resolves eumelanin and pheomelanin. Utilizing intrinsic melanin contrast in skin slices has revealed significant differences between melanoma and other lesions. © 2011 OSA: BODA/NTM/OMP/OTA.

Authors
Matthews, TE; Piletic, I; Selim, MA; Simpson, MJ; Warren, WS
MLA Citation
Matthews, TE, Piletic, I, Selim, MA, Simpson, MJ, and Warren, WS. "Beyond Pathology: Pump-probe imaging of skin slices provides additional indicators of melanoma." January 1, 2011.
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2011

Nonlinear phase contrast imaging in neuronal tissue

Authors
Samineni, P; Fischer, MC; Liu, HC; Yasuda, R; Warren, WS
MLA Citation
Samineni, P, Fischer, MC, Liu, HC, Yasuda, R, and Warren, WS. "Nonlinear phase contrast imaging in neuronal tissue." Optics InfoBase Conference Papers (2011).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2011

Beyond Pathology: Pump-probe imaging of skin slices provides additional indicators of melanoma

Authors
Matthews, TE; Piletic, I; Selim, MA; Simpson, MJ; Warren, WS
MLA Citation
Matthews, TE, Piletic, I, Selim, MA, Simpson, MJ, and Warren, WS. "Beyond Pathology: Pump-probe imaging of skin slices provides additional indicators of melanoma." Optics InfoBase Conference Papers (2011).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2011

Nonlinear phase contrast imaging in neuronal tissue

We demonstrate nonlinear phase contrast imaging in highly scattering media using rapid femtosecond pulse shaping of mode-locked laser pulses. We will also discuss potential applications of this technique for intrinsic functional neuronal imaging. © 2011 OSA: BODA/NTM/OMP/OTA.

Authors
Samineni, P; Fischer, MC; Liu, HC; Yasuda, R; Warren, WS
MLA Citation
Samineni, P, Fischer, MC, Liu, HC, Yasuda, R, and Warren, WS. "Nonlinear phase contrast imaging in neuronal tissue." Optics InfoBase Conference Papers (2011).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2011

Beyond Pathology: Pump-probe imaging of skin slices provides additional indicators of melanoma

Principal component analysis of images taken with a pump-probe scanning microscope resolves eumelanin and pheomelanin. Utilizing intrinsic melanin contrast in skin slices has revealed significant differences between melanoma and other lesions. © 2011 OSA: BODA/NTM/OMP/OTA.

Authors
Matthews, TE; Piletic, I; Selim, MA; Simpson, MJ; Warren, WS
MLA Citation
Matthews, TE, Piletic, I, Selim, MA, Simpson, MJ, and Warren, WS. "Beyond Pathology: Pump-probe imaging of skin slices provides additional indicators of melanoma." Optics InfoBase Conference Papers (2011).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2011

Accessing nonlinear phase contrast in biological tissue using femtosecond laser pulse shaping

Nonlinear imaging takes advantage of the localized nature of the interaction to achieve high spatial resolution, optical sectioning, and deeper penetration in tissue. However, nonlinear contrast (other than fluorescence or harmonic generation) is generally difficult to measure because it is overwhelmed by the large background of detected illumination light. Especially challenging to measure is the nonlinear refractive index - accessing this quantity would allow the extension of widely employed phase microscopy methods to the nonlinear regime. We have developed a technique to suppress the background in these types of measurements by using femtosecond pulse shaping to encode nonlinear interactions in background-free regions of the frequency spectrum. Using this individual pulse shaping based technique we have been able to measure self-phase modulation (SPM) in highly scattering environments, such as biological tissue, with very modest power levels. Using our measurement technique we have demonstrated strong intrinsic SPM signatures of glutamate-induced neuronal activity in hippocampal brain slices. We have also extended this measurement method to cross-phase modulation, the two-color analogue to SPM. The two-color approach dramatically improves the measurement sensitivity by reducing undesired background and associated noise. We will describe the nonlinear phase contrast measurement technique and report on its application for imaging neuronal activity. © 2011 SPIE-OSA.

Authors
Fischer, MC; Samineni, P; Li, B; Claytor, K; Warren, WS
MLA Citation
Fischer, MC, Samineni, P, Li, B, Claytor, K, and Warren, WS. "Accessing nonlinear phase contrast in biological tissue using femtosecond laser pulse shaping." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 8086 (2011).
Source
scival
Published In
Proceedings of SPIE
Volume
8086
Publish Date
2011
DOI
10.1117/12.889668

Analysis of cancer metabolism by imaging hyperpolarized nuclei: Prospects for translation to clinical research

A major challenge in cancer biology is to monitor and understand cancer metabolism in vivo with the goal of improved diagnosis and perhaps therapy. Because of the complexity of biochemical pathways, tracer methods are required for detecting specific enzyme-catalyzed reactions. Stable isotopes such as 13C or 15N with detection by nuclear magnetic resonance provide the necessary information about tissue biochemistry, but the crucial metabolites are present in low concentration and therefore are beyond the detection threshold of traditional magnetic resonance methods. A solution is to improve sensitivity by a factor of 10,000 or more by temporarily redistributing the populations of nuclear spins in a magnetic field, a process termed hyperpolarization. Although this effect is short-lived, hyperpolarized molecules can be generated in an aqueous solution and infused in vivo where metabolism generates products that can be imaged. This discovery lifts the primary constraint on magnetic resonance imaging for monitoring metabolism-poor sensitivity-while preserving the advantage of biochemical information. The purpose of this report was to briefly summarize the known abnormalities in cancer metabolism, the value and limitations of current imaging methods for metabolism, and the principles of hyperpolarization. Recent preclinical applications are described. Hyperpolarization technology is still in its infancy, and current polarizer equipment and methods are suboptimal. Nevertheless, there are no fundamental barriers to rapid translation of this exciting technology to clinical research and perhaps clinical care. © 2011 Neoplasia Press, Inc. All rights reserved.

Authors
Kurhanewicz, J; Vigneron, DB; Brindle, K; Chekmenev, EY; Comment, A; Cunningham, CH; DeBerardinis, RJ; Green, GG; Leach, MO; Rajan, SS; Rizi, RR; Ross, BD; Warren, WS; Malloy, CR
MLA Citation
Kurhanewicz, J, Vigneron, DB, Brindle, K, Chekmenev, EY, Comment, A, Cunningham, CH, DeBerardinis, RJ, Green, GG, Leach, MO, Rajan, SS, Rizi, RR, Ross, BD, Warren, WS, and Malloy, CR. "Analysis of cancer metabolism by imaging hyperpolarized nuclei: Prospects for translation to clinical research." Neoplasia 13.2 (2011): 81-97.
PMID
21403835
Source
scival
Published In
Neoplasia (New York, N.Y.)
Volume
13
Issue
2
Publish Date
2011
Start Page
81
End Page
97
DOI
10.1593/neo.101102

Pump-probe melanoma imaging: Applications to high-resolution and in-vivo microscopy

Pump-probe imaging of melanin with near-infrared pulses has been extended to two new domains: high-resolution imaging of the melanin content of melanosomes in an individual melanocyte and epi-detected in vivo microscopy of a developing melanoma. © 2011 OSA.

Authors
Wilson, JW; Matthews, TE; Degan, S; Zhang, JY; Simpson, MJ; Warren, WS
MLA Citation
Wilson, JW, Matthews, TE, Degan, S, Zhang, JY, Simpson, MJ, and Warren, WS. "Pump-probe melanoma imaging: Applications to high-resolution and in-vivo microscopy." 2011 Conference on Lasers and Electro-Optics: Laser Science to Photonic Applications, CLEO 2011 (2011).
Source
scival
Published In
2011 Conference on Lasers and Electro-Optics: Laser Science to Photonic Applications, CLEO 2011
Publish Date
2011

In vivo and ex vivo epi-mode pump-probe imaging of melanin and microvasculature

We performed epi-mode pump-probe imaging of melanin in excised human pigmented lesions and both hemoglobin and melanin in live xenograft mouse melanoma models to depths greater than 100 μm. Eumelanin and pheomelanin images, which have been previously demonstrated to differentiate melanoma from benign lesions, were acquired at the dermal-epidermal junction with cellular resolution and modest optical powers (down to 15 mW). We imaged dermal microvasculature with the same wavelengths, allowing simultaneous acquisition of melanin, hemoglobin and multiphoton autofluorescence images. Molecular pump-probe imaging of melanocytes, skin structure and microvessels allows comprehensive, non-invasive characterization of pigmented lesions. © 2011 Optical Society of America.

Authors
Matthews, TE; Wilson, JW; Degan, S; Simpson, MJ; Jin, JY; Zhang, JY; Warren, WS
MLA Citation
Matthews, TE, Wilson, JW, Degan, S, Simpson, MJ, Jin, JY, Zhang, JY, and Warren, WS. "In vivo and ex vivo epi-mode pump-probe imaging of melanin and microvasculature." Biomedical Optics Express 2.6 (2011): 1576-1583.
PMID
21698020
Source
scival
Published In
Biomedical Optics Express
Volume
2
Issue
6
Publish Date
2011
Start Page
1576
End Page
1583
DOI
10.1364/BOE.2.001576

Phase-cycling coherent anti-Stokes Raman scattering using shaped femtosecond laser pulses.

We demonstrate a homodyne coherent anti-Stokes Raman scattering (CARS) technique based on femtosecond laser pulse shaping. This technique utilizes fast phase cycling to extract nonlinear Raman signatures with a self-generated reference signal acting as a local oscillator. The local oscillator is generated at the focus and is intrinsically stable relative to the Raman signal even in highly scattering samples. We can therefore retrieve phase information from the Raman signal and can suppress the ubiquitous non-resonant background.

Authors
Li, B; Warren, WS; Fischer, MC
MLA Citation
Li, B, Warren, WS, and Fischer, MC. "Phase-cycling coherent anti-Stokes Raman scattering using shaped femtosecond laser pulses." Opt Express 18.25 (December 6, 2010): 25825-25832.
PMID
21164927
Source
pubmed
Published In
Optics express
Volume
18
Issue
25
Publish Date
2010
Start Page
25825
End Page
25832

Enhancing coherent anti-stokes Raman scattering background suppression with phase cycled structured femtosecond laser pulses

We demonstrate a homodyne coherent anti-Stokes Raman scattering technique based on femtosecond laser pulse shaping (phase-cycling). This technique utilizes a self-generated non-resonant background as a local oscillator to retrieve phase information of the Raman signal. © 2010 OSA/FiO/LS 2010.

Authors
Li, B; Warren, WS; Fischer, MC
MLA Citation
Li, B, Warren, WS, and Fischer, MC. "Enhancing coherent anti-stokes Raman scattering background suppression with phase cycled structured femtosecond laser pulses." Optics InfoBase Conference Papers (December 1, 2010).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2010

Femtosecond laser pulse shaping improves self-phase modulation measurements in scattering media

We demonstrate that our recently developed spectral re-shaping technique improves the accuracy and precision of self-phase modulation measurements in scattering media over the conventional Z-scan method. © 2010 OSA/FiO/LS 2010.

Authors
Samineni, P; Perret, Z; Warren, WS; Fischer, MC
MLA Citation
Samineni, P, Perret, Z, Warren, WS, and Fischer, MC. "Femtosecond laser pulse shaping improves self-phase modulation measurements in scattering media." Optics InfoBase Conference Papers (December 1, 2010).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2010

Nonlinear high-resolution imaging of eumelanin and pheomelanin distributions in normal skin tissue and melanoma

Two-color two-photon spectroscopy allows us for the first time to image the distribution of eumelanin and pheomelanin in tissue slices, giving histology-like detail and highlighting chemical and morphological changes in melanoma compared to benign lesions. © 2010 OSA/FiO/LS 2010.

Authors
Matthews, TE; Piletic, I; Selim, MA; Warren, WS
MLA Citation
Matthews, TE, Piletic, I, Selim, MA, and Warren, WS. "Nonlinear high-resolution imaging of eumelanin and pheomelanin distributions in normal skin tissue and melanoma." Optics InfoBase Conference Papers (December 1, 2010).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2010

Probing near-infrared photorelaxation pathways in eumelanins and pheomelanins.

Ultraviolet-visible spectroscopy readily discerns the two types of melanin pigments (eumelanin and pheomelanin), although fundamental details regarding the optical properties and pigment heterogeneity are more difficult to disentangle via analysis of the broad featureless absorption spectrum alone. We employed nonlinear transient absorption spectroscopy to study different melanin pigments at near-infrared wavelengths. Excited-state absorption, ground-state depletion, and stimulated emission signal contributions were distinguished for natural and synthetic eumelanins and pheomelanins. A starker contrast among the pigments is observed in the nonlinear excitation regime because they all exhibit distinct transient absorptive amplitudes, phase shifts, and nonexponential population dynamics spanning the femtosecond-nanosecond range. In this manner, different pigments within the pheomelanin subclass were distinguished in synthetic and human hair samples. These results highlight the potential of nonlinear spectroscopies to deliver an in situ analysis of natural melanins in tissue that are otherwise difficult to extract and purify.

Authors
Piletic, IR; Matthews, TE; Warren, WS
MLA Citation
Piletic, IR, Matthews, TE, and Warren, WS. "Probing near-infrared photorelaxation pathways in eumelanins and pheomelanins." J Phys Chem A 114.43 (November 4, 2010): 11483-11491.
Website
http://hdl.handle.net/10161/4073
PMID
20882951
Source
pubmed
Published In
The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
Volume
114
Issue
43
Publish Date
2010
Start Page
11483
End Page
11491
DOI
10.1021/jp103608d

Measurements of nonlinear refractive index in scattering media.

We have recently developed a spectral re-shaping technique to simultaneously measure nonlinear refractive index and nonlinear absorption. In this technique, the information about the nonlinearities is encoded in the frequency domain, rather than in the spatial domain as in the conventional Z-scan method. Here we show that frequency encoding is much more robust with respect to scattering. We compare spectral re-shaping and Z-scan measurements in a highly scattering environment and show that reliable spectral re-shaping measurements can be performed even in a regime that precludes standard Z-scans.

Authors
Samineni, P; Perret, Z; Warren, WS; Fischer, MC
MLA Citation
Samineni, P, Perret, Z, Warren, WS, and Fischer, MC. "Measurements of nonlinear refractive index in scattering media." Opt Express 18.12 (June 7, 2010): 12727-12735.
Website
http://hdl.handle.net/10161/4246
PMID
20588401
Source
pubmed
Published In
Optics express
Volume
18
Issue
12
Publish Date
2010
Start Page
12727
End Page
12735

Application of mixed spin iMQCs for temperature and chemical-selective imaging.

The development of accurate and non-invasive temperature imaging techniques has a wide variety of applications in fields such as medicine, chemistry and materials science. Accurate detection of temperature both in phantoms and in vivo can be obtained using iMQCs (intermolecular multiple quantum coherences), as demonstrated in a recent paper. This paper describes the underlying theory of iMQC temperature detection, as well as extensions of that work allowing not only for imaging of absolute temperature but also for imaging of analyte concentrations through chemically-selective spin density imaging.

Authors
Jenista, ER; Galiana, G; Branca, RT; Yarmolenko, PS; Stokes, AM; Dewhirst, MW; Warren, WS
MLA Citation
Jenista, ER, Galiana, G, Branca, RT, Yarmolenko, PS, Stokes, AM, Dewhirst, MW, and Warren, WS. "Application of mixed spin iMQCs for temperature and chemical-selective imaging." J Magn Reson 204.2 (June 2010): 208-218.
PMID
20303808
Source
pubmed
Published In
Journal of Magnetic Resonance
Volume
204
Issue
2
Publish Date
2010
Start Page
208
End Page
218
DOI
10.1016/j.jmr.2010.02.021

Molecular MRI for sensitive and specific detection of lung metastases.

Early and specific detection of metastatic cancer cells in the lung (the most common organ targeted by metastases) could significantly improve cancer treatment outcomes. However, the most widespread lung imaging methods use ionizing radiation and have low sensitivity and/or low specificity for cancer cells. Here we address this problem with an imaging method to detect submillimeter-sized metastases with molecular specificity. Cancer cells are targeted by iron oxide nanoparticles functionalized with cancer-binding ligands, then imaged by high-resolution hyperpolarized (3)He MRI. We demonstrate in vivo detection of pulmonary micrometastates in mice injected with breast adenocarcinoma cells. The method not only holds promise for cancer imaging but more generally suggests a fundamentally unique approach to molecular imaging in the lungs.

Authors
Branca, RT; Cleveland, ZI; Fubara, B; Kumar, CSSR; Maronpot, RR; Leuschner, C; Warren, WS; Driehuys, B
MLA Citation
Branca, RT, Cleveland, ZI, Fubara, B, Kumar, CSSR, Maronpot, RR, Leuschner, C, Warren, WS, and Driehuys, B. "Molecular MRI for sensitive and specific detection of lung metastases." Proc Natl Acad Sci U S A 107.8 (February 23, 2010): 3693-3697.
PMID
20142483
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
107
Issue
8
Publish Date
2010
Start Page
3693
End Page
3697
DOI
10.1073/pnas.1000386107

Absolute temperature imaging using intermolecular multiple quantum MRI.

PURPOSE: A review of MRI temperature imaging methods based on intermolecular multiple quantum coherences (iMQCs) is presented. Temperature imaging based on iMQCs can provide absolute temperature maps that circumvent the artefacts that other proton frequency shift techniques suffer from such as distortions to the detected temperature due to susceptibility changes and magnetic field inhomogeneities. Thermometry based on iMQCs is promising in high-fat tissues such as the breast, since it relies on the fat signal as an internal reference. This review covers the theoretical background of iMQCs, and the necessary adaptations for temperature imaging using iMQCs. MATERIALS AND METHODS: Data is presented from several papers on iMQC temperature imaging. These studies were done at 7T in both phantoms and in vivo. Results from phantoms of cream (homogeneous mixture of water and fat) are presented as well as in vivo temperature maps in obese mice. RESULTS: Thermometry based on iMQCs offers the potential to provide temperature maps which are free of artefacts due to susceptibility and magnetic field inhomogeneities, and detect temperature on an absolute scale. CONCLUSIONS: The data presented in the papers reviewed highlights the promise of iMQC-based temperature imaging in fatty tissues such as the breast. The change in susceptibility of fat with temperature makes standard proton frequency shift methods (even with fat suppression) challenging and iMQC-based imaging offers an alternative approach.

Authors
Jenista, ER; Branca, RT; Warren, WS
MLA Citation
Jenista, ER, Branca, RT, and Warren, WS. "Absolute temperature imaging using intermolecular multiple quantum MRI." Int J Hyperthermia 26.7 (2010): 725-734. (Review)
PMID
20849265
Source
pubmed
Published In
International Journal of Hyperthermia (Informa)
Volume
26
Issue
7
Publish Date
2010
Start Page
725
End Page
734
DOI
10.3109/02656736.2010.499527

Nonlinear microscopy without fluorescence: Seeing the needle in the Haystack with Femtosecond pulse shaping

Authors
Warren, WS; Piletic, I; Fischer, M; Fu, D; Samenini, P; Matthews, T
MLA Citation
Warren, WS, Piletic, I, Fischer, M, Fu, D, Samenini, P, and Matthews, T. "Nonlinear microscopy without fluorescence: Seeing the needle in the Haystack with Femtosecond pulse shaping." Optics InfoBase Conference Papers (December 1, 2009).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2009

Optimized, unequal pulse spacing in multiple echo sequences improves refocusing in magnetic resonance.

A recent quantum computing paper (G. S. Uhrig, Phys. Rev. Lett. 98, 100504 (2007)) analytically derived optimal pulse spacings for a multiple spin echo sequence designed to remove decoherence in a two-level system coupled to a bath. The spacings in what has been called a "Uhrig dynamic decoupling (UDD) sequence" differ dramatically from the conventional, equal pulse spacing of a Carr-Purcell-Meiboom-Gill (CPMG) multiple spin echo sequence. The UDD sequence was derived for a model that is unrelated to magnetic resonance, but was recently shown theoretically to be more general. Here we show that the UDD sequence has theoretical advantages for magnetic resonance imaging of structured materials such as tissue, where diffusion in compartmentalized and microstructured environments leads to fluctuating fields on a range of different time scales. We also show experimentally, both in excised tissue and in a live mouse tumor model, that optimal UDD sequences produce different T(2)-weighted contrast than do CPMG sequences with the same number of pulses and total delay, with substantial enhancements in most regions. This permits improved characterization of low-frequency spectral density functions in a wide range of applications.

Authors
Jenista, ER; Stokes, AM; Branca, RT; Warren, WS
MLA Citation
Jenista, ER, Stokes, AM, Branca, RT, and Warren, WS. "Optimized, unequal pulse spacing in multiple echo sequences improves refocusing in magnetic resonance." J Chem Phys 131.20 (November 28, 2009): 204510-.
Website
http://hdl.handle.net/10161/3315
PMID
19947697
Source
pubmed
Published In
Journal of Chemical Physics
Volume
131
Issue
20
Publish Date
2009
Start Page
204510
DOI
10.1063/1.3263196

Estimation of molar absorptivities and pigment sizes for eumelanin and pheomelanin using femtosecond transient absorption spectroscopy.

Fundamental optical and structural properties of melanins are not well understood due to their poor solubility characteristics and the chemical disorder present during biomolecular synthesis. We apply nonlinear transient absorption spectroscopy to quantify molar absorptivities for eumelanin and pheomelanin and thereby get an estimate for their average pigment sizes. We determine that pheomelanin exhibits a larger molar absorptivity at near IR wavelengths (750 nm), which may be extended to shorter wavelengths. Using the molar absorptivities, we estimate that melanin pigments contain approximately 46 and 28 monomer units for eumelanin and pheomelanin, respectively. This is considerably larger than the oligomeric species that have been recently proposed to account for the absorption spectrum of eumelanin and illustrates that larger pigments comprise a significant fraction of the pigment distribution.

Authors
Piletic, IR; Matthews, TE; Warren, WS
MLA Citation
Piletic, IR, Matthews, TE, and Warren, WS. "Estimation of molar absorptivities and pigment sizes for eumelanin and pheomelanin using femtosecond transient absorption spectroscopy." J Chem Phys 131.18 (November 14, 2009): 181106-.
PMID
19916591
Source
pubmed
Published In
Journal of Chemical Physics
Volume
131
Issue
18
Publish Date
2009
Start Page
181106
DOI
10.1063/1.3265861

iDQC anisotropy map imaging for tumor tissue characterization in vivo.

Intermolecular double quantum coherences (iDQCs), signals that result from simultaneous transitions of two or more separated spins, are known to produce images that are highly sensitive to subvoxel structure, particularly local anisotropy. Here we demonstrate how iDQCs signal can be used to efficiently detect the anisotropy created in breast tumor tissues and prostate tumor tissues by targeted (LHRH-conjugated) superparamagnetic nanoparticles (SPIONs), thereby distinguishing the necrotic area from the surrounding tumor tissue.

Authors
Branca, RT; Chen, YM; Mouraviev, V; Galiana, G; Jenista, ER; Kumar, C; Leuschner, C; Warren, WS
MLA Citation
Branca, RT, Chen, YM, Mouraviev, V, Galiana, G, Jenista, ER, Kumar, C, Leuschner, C, and Warren, WS. "iDQC anisotropy map imaging for tumor tissue characterization in vivo." Magn Reson Med 61.4 (April 2009): 937-943.
PMID
19215050
Source
pubmed
Published In
Magnetic Resonance in Medicine
Volume
61
Issue
4
Publish Date
2009
Start Page
937
End Page
943
DOI
10.1002/mrm.21925

Increasing hyperpolarized spin lifetimes through true singlet eigenstates.

The sensitivity limitations for magnetic resonance imaging of organic molecules have recently been addressed by hyperpolarization methods, which prepare excess nuclear spin polarization. This approach can increase sensitivity by orders of magnitude, but the enhanced signal relaxes away in tens of seconds, even in favorable cases. Here we show theoretically that singlet states between strongly coupled spins in molecules can be used to store and retrieve population in very-long-lived disconnected eigenstates, as long as the coupling between the spins substantially exceeds both the couplings to other spins and the resonance frequency difference between them. Experimentally, 2,3-carbon-13-labeled diacetyl has a disconnected eigenstate that can store population for minutes and is read out by hydration to make the two spins inequivalent.

Authors
Warren, WS; Jenista, E; Branca, RT; Chen, X
MLA Citation
Warren, WS, Jenista, E, Branca, RT, and Chen, X. "Increasing hyperpolarized spin lifetimes through true singlet eigenstates." Science 323.5922 (March 27, 2009): 1711-1714.
PMID
19325112
Source
pubmed
Published In
Science
Volume
323
Issue
5922
Publish Date
2009
Start Page
1711
End Page
1714
DOI
10.1126/science.1167693

Hyperpolarized carbon-carbon intermolecular multiple quantum coherences.

Intermolecular multiple quantum coherences (iMQCs) can provide unique contrast with sub-voxel resolution. However, the characteristic growth rate of iMQCs mostly limits these effects to either hydrogen or hydrogen-coupled systems for thermally polarized samples. Hyperpolarization techniques such as dynamic nuclear polarization (DNP) allow for significant increases in the carbon signal (even more signal than that from hydrogen), making carbon iMQCs achievable. We present the first intermolecular multiple quantum signal between two carbon nuclei.

Authors
Jenista, ER; Branca, RT; Warren, WS
MLA Citation
Jenista, ER, Branca, RT, and Warren, WS. "Hyperpolarized carbon-carbon intermolecular multiple quantum coherences." J Magn Reson 196.1 (January 2009): 74-77.
PMID
18926750
Source
pubmed
Published In
Journal of Magnetic Resonance
Volume
196
Issue
1
Publish Date
2009
Start Page
74
End Page
77
DOI
10.1016/j.jmr.2008.09.027

LHRH-functionalized superparamagnetic iron oxide nanoparticles for breast cancer targeting and contrast enhancement in MRI

This paper shows that superparamagnetic iron oxide nanoparticles (SPIONs) conjugated to luteinizing hormone releasing hormone (LHRH) (LHRH-SPIONs), can be used to target breast cancer cells. They also act as contrast enhancement agents during the magnetic resonance imaging of breast cancer xenografts. A combination of transmission electron microscopy (TEM) and spectrophotometric analysis was used in our experiments, to investigate the specific accumulation of the functionalized superparamagnetic iron oxide nanoparticles (SPIONs) in cancer cells. The contrast enhancement of conventional T2 images obtained from the tumor tissue and of breast cancer xenograft bearing mice is shown to be much greater than that in saline controls, when the tissues were injected with LHRH-SPIONs. Magnetic anisotropy multi-CRAZED images of tissues extracted from mice injected with SPIONs were also found to have enhanced MRI contrast in breast cancer xenografts and metastases in the lungs. © 2008.

Authors
Meng, J; Fan, J; Galiana, G; Branca, RT; Clasen, PL; Ma, S; Zhou, J; Leuschner, C; Kumar, CSSR; Hormes, J; Otiti, T; Beye, AC; Harmer, MP; Kiely, CJ; Warren, W; Haataja, MP; Soboyejo, WO
MLA Citation
Meng, J, Fan, J, Galiana, G, Branca, RT, Clasen, PL, Ma, S, Zhou, J, Leuschner, C, Kumar, CSSR, Hormes, J, Otiti, T, Beye, AC, Harmer, MP, Kiely, CJ, Warren, W, Haataja, MP, and Soboyejo, WO. "LHRH-functionalized superparamagnetic iron oxide nanoparticles for breast cancer targeting and contrast enhancement in MRI." Materials Science and Engineering C 29.4 (2009): 1467-1479.
Source
scival
Published In
Materials Science and Engineering: C
Volume
29
Issue
4
Publish Date
2009
Start Page
1467
End Page
1479
DOI
10.1016/j.msec.2008.09.039

Nonlinear absorption microscopy

For the past two decades, nonlinear microscopy has been developed to overcome the scattering problem in thick tissue imaging. Owing to its increased imaging depth and high spatial resolution, nonlinear microscopy becomes the first choice for imaging living tissues. The use of nonlinear optical effects not only facilitates the signal originating from an extremely small volume defined by light focusing but also provides novel contrast mechanisms with molecular specificity. Nonlinear absorption is a nonlinear optical effect in which the absorption coefficient depends on excitation intensity. As a commonly used spectroscopy tool, nonlinear absorption measurement uncovers many photophysical and photochemical processes correlated with electronic states of molecules. Recently we have been focusing on adapting this spectroscopy method to a microscopy imaging technique. The effort leads to a novel modality in nonlinear microscopy - nonlinear absorption microscopy. This article summarizes the principles and instrumentation of this imaging technique and highlights some of the recent progress in applying it to imaging skin pigmentation and microvasculature under ex vivo or in vivo conditions. © 2008 The American Society of Photobiology.

Authors
Ye, T; Fu, D; Warren, WS
MLA Citation
Ye, T, Fu, D, and Warren, WS. "Nonlinear absorption microscopy." Photochemistry and Photobiology 85.3 (2009): 631-645.
PMID
19170931
Source
scival
Published In
Photochemistry & Photobiology
Volume
85
Issue
3
Publish Date
2009
Start Page
631
End Page
645
DOI
10.1111/j.1751-1097.2008.00514.x

Solvent suppression without crosspeak attenuation in iZQC experiments

The observation of solvent-solute iZQC peaks is often hampered by strong nearby solvent peaks. Previous researchers have overcome this problem by adding conventional solvent suppression modules during the dipolar evolution time. Here we show that these solvent suppression modules refocus the dipolar field and lead to a substantial signal intensity reduction, which is particularly damaging for the detection of low concentration species. We analyze, in detail, the effect of such modules on the signal formation, and demonstrate a method for solvent suppression that does not interfere with dipolar field evolution, leading to cleaner spectra. © 2009 Elsevier B.V. All rights reserved.

Authors
Branca, RT; Warren, WS
MLA Citation
Branca, RT, and Warren, WS. "Solvent suppression without crosspeak attenuation in iZQC experiments." Chemical Physics Letters 470.4-6 (2009): 325-331.
Source
scival
Published In
Chemical Physics Letters
Volume
470
Issue
4-6
Publish Date
2009
Start Page
325
End Page
331
DOI
10.1016/j.cplett.2009.01.063

Tilting after dutch windmills: Probably no long-lived davydov solitons in proteins

We present a summary of picosecond pump-probe and photon echo experiments in the mid-IR at 6 μm on the protein myoglobin. The intriguing temperature dependence of the amide I band in Mb is rather similar to the temperature dependence of the amide I band of acetanilide, the molecule that launched Al Scott down the road of looking for Davydov solitons in biology. Alas, after much effort, we believe the data show that there is no long-lived Davydov soliton, at least in myoglobin. © 2009 Springer Science+Business Media B.V.

Authors
Austin, RH; Xie, A; Fu, D; Warren, WW; Redlich, B; Meer, LVD
MLA Citation
Austin, RH, Xie, A, Fu, D, Warren, WW, Redlich, B, and Meer, LVD. "Tilting after dutch windmills: Probably no long-lived davydov solitons in proteins." Journal of Biological Physics 35.1 (2009): 91-101.
Source
scival
Published In
Journal of Biological Physics
Volume
35
Issue
1
Publish Date
2009
Start Page
91
End Page
101
DOI
10.1007/s10867-009-9130-7

Enhanced nonlinear magnetic resonance signals via square wave dipolar fields.

This report introduces a new approach that enhances nonlinear solution magnetic resonance signals from intermolecular dipolar interactions. The resulting signals can theoretically be as large as the full equilibrium magnetization. Simple, readily implemented pulse sequences using square-wave magnetization modulation simultaneously refocus all even order intermolecular multiple quantum coherences, leading to a substantial net signal enhancement, complex nonlinear dynamics, and improved structural sensitivity under realistic conditions.

Authors
Branca, RT; Galiana, G; Warren, WS
MLA Citation
Branca, RT, Galiana, G, and Warren, WS. "Enhanced nonlinear magnetic resonance signals via square wave dipolar fields." J Chem Phys 129.5 (August 7, 2008): 054502-.
PMID
18698909
Source
pubmed
Published In
Journal of Chemical Physics
Volume
129
Issue
5
Publish Date
2008
Start Page
054502
DOI
10.1063/1.2962976

Rapid pulse shaping with homodyne detection for measuring nonlinear optical signals.

We have designed a common-mode interferometric acousto-optic pulse shaper that is capable of shaping individual pulses differently from a mode-locked laser. The design enables the measurement of weak nonlinear optical signals such as two-photon absorption and self-phase modulation at megahertz rates. The experimental apparatus incorporates homodyne detection as a means of resolving the phase of the detected signals. The fast data acquisition rate and the ability to perform measurements in scattering media make this experimental apparatus amenable to imaging applications analogous to measurements of two-photon fluorescence using a mode-locked laser.

Authors
Piletic, IR; Fischer, MC; Samineni, P; Yurtsever, G; Warren, WS
MLA Citation
Piletic, IR, Fischer, MC, Samineni, P, Yurtsever, G, and Warren, WS. "Rapid pulse shaping with homodyne detection for measuring nonlinear optical signals." Opt Lett 33.13 (July 1, 2008): 1482-1484.
PMID
18594672
Source
pubmed
Published In
Optics Letters
Volume
33
Issue
13
Publish Date
2008
Start Page
1482
End Page
1484

Simultaneous self-phase modulation and two-photon absorption measurement by a spectral homodyne Z-scan method.

We developed a technique to simultaneously measure self-phase modulation and two-photon absorption using shaped femtosecond laser pulses. In the conventional Z-scan measurement technique the amount of nonlinearity is determined by measuring the change in shape and intensity of a transmitted laser beam. In contrast, our method sensitively measures nonlinearity-induced changes in the pulse spectrum. In this work we demonstrate the technique in nonlinear absorptive and dispersive samples, quantify the obtained signal, and compare the measurements with traditional Z-scans. This technique is capable of measuring these nonlinearities in highly scattering samples.

Authors
Fischer, MC; Liu, HC; Piletic, IR; Warren, WS
MLA Citation
Fischer, MC, Liu, HC, Piletic, IR, and Warren, WS. "Simultaneous self-phase modulation and two-photon absorption measurement by a spectral homodyne Z-scan method." Opt Express 16.6 (March 17, 2008): 4192-4205.
PMID
18542515
Source
pubmed
Published In
Optics express
Volume
16
Issue
6
Publish Date
2008
Start Page
4192
End Page
4205

Self-phase modulation signatures of neuronal activity.

We use phase-sensitive detection of spectral hole refilling to demonstrate strong novel intrinsic nonlinear signatures of neuronal activation in hippocampal brain slices. The ability to gain access to this fundamentally new intrinsic contrast with modest power levels suggests a new approach to in vivo neural imaging. We expect that we can extrapolate our method to high spatial and temporal resolution in deep tissue while retaining the noninvasive character.

Authors
Fischer, MC; Liu, HC; Piletic, IR; Escobedo-Lozoya, Y; Yasuda, R; Warren, WS
MLA Citation
Fischer, MC, Liu, HC, Piletic, IR, Escobedo-Lozoya, Y, Yasuda, R, and Warren, WS. "Self-phase modulation signatures of neuronal activity." Opt Lett 33.3 (February 1, 2008): 219-221.
PMID
18246134
Source
pubmed
Published In
Optics Letters
Volume
33
Issue
3
Publish Date
2008
Start Page
219
End Page
221

New nonlinear signatures in spectroscopy and imaging

Ultrafast laser pulse shaping makes it possible to observe nonlinear signatures, such as self phase modulation and sum frequency absorption, at safe laser powers for tissue. Neuronal activation and melanoma diagnosis are two early targets. ©2008 Optical Society of America.

Authors
Warren, WS; Fischer, M; Fu, D; Ye, T; Piletic, I; Matthews, T
MLA Citation
Warren, WS, Fischer, M, Fu, D, Ye, T, Piletic, I, and Matthews, T. "New nonlinear signatures in spectroscopy and imaging." Optics InfoBase Conference Papers (January 1, 2008).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2008

Accessing nonlinear contrast in imaging using rapid pulse shaping techniques

We have designed an interferometric acousto-optic pulse shaper capable of shaping individual pulses differently from a mode-locked laser. The design enables the measurement of weak nonlinear optical signals at megahertz (MHz) rates for imaging applications. © 2008 Optical Society of America.

Authors
Piletic, IR; Fischer, MC; Samineni, P; Warren, WS
MLA Citation
Piletic, IR, Fischer, MC, Samineni, P, and Warren, WS. "Accessing nonlinear contrast in imaging using rapid pulse shaping techniques." Optics InfoBase Conference Papers (January 1, 2008).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2008

Femtosecond laser pulse shaping for molecular imaging in biological tissue

Recently developed ultrafast laser pulse shaping technology allows highsensitivity measurements of nonlinear optical effects in highly scattering media. We present applications of these techniques to extract intrinsic structural, metabolic and functional contrast in biological tissue. © 2008 OSA.

Authors
Fischer, MC; Liu, HC; Fu, D; Semineni, P; Matthews, T; Piletic, I; Warren, WS
MLA Citation
Fischer, MC, Liu, HC, Fu, D, Semineni, P, Matthews, T, Piletic, I, and Warren, WS. "Femtosecond laser pulse shaping for molecular imaging in biological tissue." Optics InfoBase Conference Papers (January 1, 2008).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2008

Intrinsic nonlinear optical signatures of neuronal activity

Using novel femtosecond laser pulse shaping techniques and a virtually background-free detection strategy we demonstrate strong self-phase modulation signatures of neuronal activity in hippocampal brain slices without the use of exogenous contrast agents. © 2008 Optical Society of America.

Authors
Liu, HC; Fischer, MC; Samineni, P; Escobedo-Lozoya, Y; Yasuda, R; Warren, WS
MLA Citation
Liu, HC, Fischer, MC, Samineni, P, Escobedo-Lozoya, Y, Yasuda, R, and Warren, WS. "Intrinsic nonlinear optical signatures of neuronal activity." Optics InfoBase Conference Papers (January 1, 2008).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2008

Stimulated raman scattering with shaped ultrafast pulse trains

We explore the possibility of using Stimulated Raman (SRS) as a new imaging contrast and compared it to two photon absorption (TPA). Potential advantages over coherent anti-stokes Raman scattering (CARS) imaging are discussed. © 2008 Optical Society of America.

Authors
Fu, D; Warren, WS
MLA Citation
Fu, D, and Warren, WS. "Stimulated raman scattering with shaped ultrafast pulse trains." Optics InfoBase Conference Papers (January 1, 2008).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2008

New nonlinear signatures in spectroscopy and imaging

Ultrafast laser pulse shaping makes it possible to observe nonlinear signatures, such as self phase modulation and sum frequency absorption, at safe laser powers for tissue. Neuronal activation and melanoma diagnosis are two early targets. © 2008 Optical Society of America.

Authors
Warren, WS; Fischer, M; Fu, D; Ye, T; Piletic, I; Matthews, T
MLA Citation
Warren, WS, Fischer, M, Fu, D, Ye, T, Piletic, I, and Matthews, T. "New nonlinear signatures in spectroscopy and imaging." Optics InfoBase Conference Papers (January 1, 2008).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2008

New nonlinear signatures in spectroscopy and imaging

Ultrafast laser pulse shaping makes it possible to observe nonlinear signatures, such as self phase modulation and sum frequency absorption, at safe laser powers for tissue. Neuronal activation and melanoma diagnosis are two early targets. © 2008 Optical Society of America.

Authors
Warren, WS; Fischer, M; Fu, D; Ye, T; Piletic, I; Matthews, T
MLA Citation
Warren, WS, Fischer, M, Fu, D, Ye, T, Piletic, I, and Matthews, T. "New nonlinear signatures in spectroscopy and imaging." 2008 Conference on Quantum Electronics and Laser Science Conference on Lasers and Electro-Optics, CLEO/QELS (2008).
Source
scival
Published In
2008 Conference on Quantum Electronics and Laser Science Conference on Lasers and Electro-Optics, CLEO/QELS
Publish Date
2008
DOI
10.1109/CLEO.2008.4552392

New nonlinear signatures in spectroscopy and imaging

Ultrafast laser pulse shaping makes it possible to observe nonlinear signatures, such as self phase modulation and sum frequency absorption, at safe laser powers for tissue. Neuronal activation and melanoma diagnosis are two early targets. © 2008 Optical Society of America.

Authors
Warren, WS; Fischer, M; Fu, D; Ye, T; Piletic, I; Matthews, T
MLA Citation
Warren, WS, Fischer, M, Fu, D, Ye, T, Piletic, I, and Matthews, T. "New nonlinear signatures in spectroscopy and imaging." Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series (2008).
Source
scival
Published In
Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series
Publish Date
2008
DOI
10.1109/QELS.2008.4552901

Accurate temperature imaging based on intermolecular coherences in magnetic resonance

Conventional magnetic resonance methods that provide interior temperature profiles, which find use in clinical applications such as hyperthermic therapy, can develop inaccuracies caused by the inherently inhomogeneous magnetic field within tissues or by probe dynamics, and work poorly in important applications such as fatty tissues. We present a magnetic resonance method that is suitable for imaging temperature in a wide range of environments. It uses the inherently sharp resonances of intermolecular zero-quantum coherences, in this case flipping up a water spin while flipping down a nearby fat spin. We show that this method can rapidly and accurately assign temperatures in vivo on an absolute scale.

Authors
Galiana, G; Branca, RT; Jenista, ER; Warren, WS
MLA Citation
Galiana, G, Branca, RT, Jenista, ER, and Warren, WS. "Accurate temperature imaging based on intermolecular coherences in magnetic resonance." Science 322.5900 (2008): 421-424.
PMID
18927389
Source
scival
Published In
Science
Volume
322
Issue
5900
Publish Date
2008
Start Page
421
End Page
424
DOI
10.1126/science.1163242

Label-free in vivo optical imaging of microvasculature and oxygenation level

The ability to perform high-resolution imaging of microvasculature and its oxygenation is very important in studying early tumor development. Toward this goal, we improved upon our excited state absorption (ESA)-based imaging technique to allow us to not only image hemoglobin directly but also differentiate between oxy- and deoxyhemoglobin in tissue. We demonstrate the separation of arterioles from venules in a live nude mouse ear using our imaging technique. © 2008 Society of Photo-Optical Instrumentation Engineers.

Authors
Fu, D; Matthews, TE; Ye, T; Piletic, IR; Warren, WS
MLA Citation
Fu, D, Matthews, TE, Ye, T, Piletic, IR, and Warren, WS. "Label-free in vivo optical imaging of microvasculature and oxygenation level." Journal of Biomedical Optics 13.4 (2008).
PMID
19021307
Source
scival
Published In
Journal of Biomedical Optics
Volume
13
Issue
4
Publish Date
2008
DOI
10.1117/1.2968260

Probing skin pigmentation changes with transient absorption imaging of eumelanin and pheomelanin

As some of the most ubiquitous and biologically important natural pigments, melanins play essential roles in the photoprotection of skin. Changes in melanin production could potentially be useful for clinical diagnosis of the progression stage of melanoma. Previously we demonstrated a new method for imaging melanin distribution in tissue with two-color transient absorption microscopy. Here we extend this study to longer wavelengths and show that we are able to image melanin in fixed thin skin slices with higher signal-to-noise ratios (SNRs) and demonstrate epimode imaging. We show that both photothermal effects and long-lived excited states can contribute to the long-lived signal. Eumelanin and pheomelanin exhibit markedly different long-lived excited state absorption. This difference should enable us to map out their respective distribution in tissue samples with subcellular resolution. This technique could provide valuable information in diagnosing the malignant transformation of melanocytes. © 2008 Society of Photo-Optical Instrumentation Engineers.

Authors
Fu, D; Ye, T; Matthews, TE; Grichnik, J; Hong, L; Simon, JD; Warren, WS
MLA Citation
Fu, D, Ye, T, Matthews, TE, Grichnik, J, Hong, L, Simon, JD, and Warren, WS. "Probing skin pigmentation changes with transient absorption imaging of eumelanin and pheomelanin." Journal of Biomedical Optics 13.5 (2008).
PMID
19021416
Source
scival
Published In
Journal of Biomedical Optics
Volume
13
Issue
5
Publish Date
2008
DOI
10.1117/1.2976424

Propagation of complex shaped ultrafast pulses in highly optically dense samples

We examine the propagation of shaped (amplitude- and frequency-modulated) ultrafast laser pulses through optically dense rubidium vapor. Pulse reshaping, stimulated emission dynamics, and residual electronic excitation all strongly depend on the laser pulse shape. For example, frequency swept pulses, which produce adiabatic passage in the optically thin limit (independent of the sign of the frequency sweep), behave unexpectedly in optically dense samples. Paraxial Maxwell optical Bloch equations can model our ultrafast pulse propagation results well and provide insight. © 2008 American Institute of Physics.

Authors
Davis, JC; Fetterman, MR; Warren, WS; Goswami, D
MLA Citation
Davis, JC, Fetterman, MR, Warren, WS, and Goswami, D. "Propagation of complex shaped ultrafast pulses in highly optically dense samples." Journal of Chemical Physics 128.15 (2008).
PMID
18433214
Source
scival
Published In
Journal of Chemical Physics
Volume
128
Issue
15
Publish Date
2008
DOI
10.1063/1.2894871

Two-photon absorption and transient photothermal imaging of pigments in tissues

As a main pigment in skin tissues, melanin plays an important role in photo-protecting skin from UV radiation. However, melanogenesis may be altered due to disease or environmental factors; for example, sun exposure may cause damage and mutation of melanocytes and induce melanoma. Imaging pigmentation changes may provide invaluable information to catch the malignant transformation in its early stage and in turn improve the prognosis of patients. We have demonstrated previously that transmission mode, two-photon, one- or two-color absorption microscopy could provide remarkable contrast in imaging melanin in skin. In this report we demonstrate significantly improved sensitivity, so that we are now able to image in epi-mode (or back reflection) in two-photon absorption. This improvement makes possible for us to characterize the different types of pigmentation on the skin in vivo at virtually any location. Another finding is that we can also image transient photothermal dynamics due to the light absorption of melanin. By carefully choosing excitation and probe wavelengths, we might be able to image melanin in different structures under different micro-environments in skin, which could provide useful photochemical and photophysical insights in understanding how pigments are involved in photoprotection and photodamage of cells.

Authors
Ye, T; Fu, D; Matthews, TE; Hong, L; Simon, JD; Warren, WS
MLA Citation
Ye, T, Fu, D, Matthews, TE, Hong, L, Simon, JD, and Warren, WS. "Two-photon absorption and transient photothermal imaging of pigments in tissues." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 6842 (2008).
Source
scival
Published In
Proceedings of SPIE
Volume
6842
Publish Date
2008
DOI
10.1117/12.764248

Label free high resolution in vivo optical imaging of microvessels

We have demonstrated a new optical microscopy technique for imaging microvasculature without any labeling. With a very sensitive two-color excited state absorption (ESA) measurement method, we demonstrated that oxy-hemoglobin and deoxy-hemoglobin show distinct excited state dynamics. Since this is a collinear measurement, we can readily apply it to the microscopic study of biological tissue. We have already demonstrated in vivo imaging of blood vessels in the nude mouse ear. Here we optimized the excitation and detection pulse train toward longer wavelengths, where tissue scatters less and greater penetration depth can be obtained. More importantly, we are able to separate arterioles from venules by employing different pump and probe wavelength combinations. This provides a powerful method to image blood vessels and their oxygenation level at the same time with micrometer resolution.

Authors
Fu, D; Matthews, TE; Ye, T; Warren, WS
MLA Citation
Fu, D, Matthews, TE, Ye, T, and Warren, WS. "Label free high resolution in vivo optical imaging of microvessels." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 6860 (2008).
Source
scival
Published In
Proceedings of SPIE
Volume
6860
Publish Date
2008
DOI
10.1117/12.763969

Signal enhancement in CRAZED experiments.

Many of the promising applications of the CRAZED (COSY Revamped with Asymmetric Z-gradient Echo Detection) experiments are in biomedical and clinical technologies. In tissue, however, signal from the typical CRAZED experiment is largely limited by transverse relaxation. When relaxation is included, the maximum achievable signal from a prototypical CRAZED sequence, in the linear regime, is proportional to T(2)/tau(d). This means that for samples with a short T(2), as encountered in vivo, signals from intermolecular multiple-quantum coherences (iMQCs) reach very diminished signal intensities. While relaxation is generally regarded as a fundamental constraint, we show here that when T(2) is short but T(1) is long, as in tissue, there are simple sequence modifications that can increase signal beyond the T(2) limit. To better utilize the available signal intensity from iMQCs we propose a method to substitute part of the transverse magnetization with the longitudinally modulated magnetization. In this paper we show, with both simulations and experimental results, that in the presence of strong transverse relaxation the standard CRAZED scheme is not the optimal method for observing iMQCs, and can be improved upon with simple modifications.

Authors
Branca, RT; Galiana, G; Warren, WS
MLA Citation
Branca, RT, Galiana, G, and Warren, WS. "Signal enhancement in CRAZED experiments." J Magn Reson 187.1 (July 2007): 38-43.
PMID
17448714
Source
pubmed
Published In
Journal of Magnetic Resonance
Volume
187
Issue
1
Publish Date
2007
Start Page
38
End Page
43
DOI
10.1016/j.jmr.2007.02.017

Two-photon absorption imaging of hemoglobin

We demonstrated that both oxyhemoglobin and deoxyhemoglobin has sequential twophoton absorption properties that can serve as endogenous contrasts in microvasculature imaging. They can also be differentiated through their different excited state dynamics. © 2007 Optical Society of America.

Authors
Fu, D; Matthews, TE; Ye, T; Yurtserver, G; Warren, WS
MLA Citation
Fu, D, Matthews, TE, Ye, T, Yurtserver, G, and Warren, WS. "Two-photon absorption imaging of hemoglobin." Optics InfoBase Conference Papers (January 1, 2007).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2007

Novel nonlinear contrast improves deep-tissue microscopy

Femtosecond laser pulse and pulse-train shaping allow detection of new nonlinear effects, with modest powers, making new biomarkers accessible and permitting deeper tissue imaging than conventional microscopy. The most developed of these technique create light at a new wavelength, which can then be separated from the exciting laser. While the two photon fluorescence (TPF) can be induced by continuous wave lasers, the vast majority of studies use short laser pulses to achieve high peak power with relatively low tissue damage from average power dissipation. Two photon absorption (TPA) and self-phase modulation (SPM) are the two most important single-wavelength effect for the purpose of tissue engineering. TPA is more effective on the intense pulses than on the weak ones, and it thus distorts the amplitude modulation, creating extra sidebands. Microscopic resolution to depths of about 1mm should be achievable in most tissues with far more physiological contrast than conventional microscopy.

Authors
Warren, WS; Fischer, MC; Tong, Y
MLA Citation
Warren, WS, Fischer, MC, and Tong, Y. "Novel nonlinear contrast improves deep-tissue microscopy." Laser Focus World 43.6 (2007): 99-103.
Source
scival
Published In
Laser Focus World
Volume
43
Issue
6
Publish Date
2007
Start Page
99
End Page
103

High-resolution in vivo imaging of blood vessels without labeling

We demonstrate that both oxyhemoglobin and deoxyhemoglobin have sequential two-color, two-photon absorption properties that can serve as endogenous contrasts in microvasculature imaging. Using a sensitive modulation transfer technique, we are able to image hemoglobin in red blood cells with micrometer resolution, both in vitro and in vivo. We show that excellent contrast from hemoglobin without any labeling can be obtained in tissue. © 2007 Optical Society of America.

Authors
Fu, D; Ye, T; Matthews, TE; Chen, BJ; Yurtserver, G; Warren, WS
MLA Citation
Fu, D, Ye, T, Matthews, TE, Chen, BJ, Yurtserver, G, and Warren, WS. "High-resolution in vivo imaging of blood vessels without labeling." Optics Letters 32.18 (2007): 2641-2643.
PMID
17873920
Source
scival
Published In
Optics Letters
Volume
32
Issue
18
Publish Date
2007
Start Page
2641
End Page
2643
DOI
10.1364/OL.32.002641

Self-phase modulation and two-photon absorption imaging of cells and active neurons

Even though multi-photon fluorescence microscopy offers higher resolution and better penetration depth than traditional fluorescence microscopy, its use is restricted to the detection of molecules that fluoresce. Two-photon absorption (TPA) imaging can provide contrast in non-fluorescent molecules while retaining the high resolution and sectioning capabilities of nonlinear imaging modalities. In the long-wavelength water window, tissue TPA is dominated by the endogenous molecules melanin and hemoglobin with an almost complete absence of endogenous two-photon fluorescence. A complementary nonlinear contrast mechanism is self-phase modulation (SPM), which can provide intrinsic signatures that can depend on local tissue anisotropy, chemical environment, or other structural properties. We have developed a spectral hole refilling measurement technique for TPA and SPM measurements using shaped ultrafast laser pulses. Here we report on a microscopy setup to simultaneously acquire 3D, high-resolution TPA and SPM images. We have acquired data in mounted B16 melanoma cells with very modest laser power levels. We will also discuss the possible application of this measurement technique to neuronal imaging. Since SPM is sensitive to material structure we can expect SPM properties of neurons to change during neuronal firing. Using our hole-refilling technique we have now demonstrated strong novel intrinsic nonlinear signatures of neuronal activation in a hippocampal brain slice. The observed changes in nonlinear signal upon collective activation were up to factors of two, unlike other intrinsic optical signal changes on the percent level. These results show that TPA and SPM imaging can provide important novel functional contrast in tissue using very modest power levels suitable for in vivo applications.

Authors
Fischer, MC; Liu, H; Piletic, IR; Ye, T; Yasuda, R; Warren, WS
MLA Citation
Fischer, MC, Liu, H, Piletic, IR, Ye, T, Yasuda, R, and Warren, WS. "Self-phase modulation and two-photon absorption imaging of cells and active neurons." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 6442 (2007).
Source
scival
Published In
Proceedings of SPIE
Volume
6442
Publish Date
2007
DOI
10.1117/12.698693

Study of diffusion in erythrocyte suspension using internal magnetic field inhomogeneity

Transport of water and ions through cell membranes plays an important role in cell metabolism. We demonstrate a novel technique to measure water transport dynamics using erythrocyte suspensions as an example. This technique takes advantage of inhomogenous internal magnetic field created by the magnetic susceptibility contrast between the erythrocytes and plasma. The decay of longitudinal magnetization due to diffusion in this internal field reveals multi-exponential behavior, with one component corresponding to the diffusive exchange of water across erythrocyte membrane. The membrane permeability is obtained from the exchange time constant and is in good agreement with the literature values. As compared to the other methods, this technique does not require strong gradients of magnetic field or contrast agents and, potentially, can be applied in vivo. © 2007 Elsevier Inc. All rights reserved.

Authors
Lisitza, NV; Warren, WS; Song, Y-Q
MLA Citation
Lisitza, NV, Warren, WS, and Song, Y-Q. "Study of diffusion in erythrocyte suspension using internal magnetic field inhomogeneity." Journal of Magnetic Resonance 187.1 (2007): 146-154.
PMID
17498984
Source
scival
Published In
Journal of Magnetic Resonance
Volume
187
Issue
1
Publish Date
2007
Start Page
146
End Page
154
DOI
10.1016/j.jmr.2007.04.010

Magnetic resonance microscopic imaging based on high-order intermolecular multiple-quantum coherences

Most imaging studies using intermolecular multiple-quantum coherences (iMQCs) have focused on the two-spin dipolar interactions - zero and double quantum coherences. Here, we report the results of various experimental studies to assess the feasibility of magnetic resonance microscopy with high-order iMQCs in model systems at 7 and 14 T. Experimental results demonstrated that the iMQC microscopic images with high coherence orders are readily observable at high field and have unique contrast depending on the sample microstructure and coherence order. © 2007.

Authors
Cho, J-H; Ahn, S; Lee, C; Hong, KS; Chung, K-C; Chang, S-K; Cheong, C; Warren, WS
MLA Citation
Cho, J-H, Ahn, S, Lee, C, Hong, KS, Chung, K-C, Chang, S-K, Cheong, C, and Warren, WS. "Magnetic resonance microscopic imaging based on high-order intermolecular multiple-quantum coherences." Magnetic Resonance Imaging 25.5 (2007): 626-633.
PMID
17540273
Source
scival
Published In
Magnetic Resonance Imaging
Volume
25
Issue
5
Publish Date
2007
Start Page
626
End Page
633
DOI
10.1016/j.mri.2006.09.005

Intermolecular multiple quantum MR thermography

Authors
Galiana, G; Branca, RT; Jenista, ER; Warren, WS
MLA Citation
Galiana, G, Branca, RT, Jenista, ER, and Warren, WS. "Intermolecular multiple quantum MR thermography." Proceedings of the ASME Summer Bioengineering Conference 2007, SBC 2007 (2007): 71-72.
Source
scival
Published In
Proceedings of the ASME Summer Bioengineering Conference 2007, SBC 2007
Publish Date
2007
Start Page
71
End Page
72

Two-color, two-photon, and excited-state absorption microscopy

We develop a new approach in imaging nonfluorescent species with two-color two-photon and excited state absorption microscopy. If one of two synchronized mode-locked pulse trains at different colors is intensity modulated, the modulation transfers to the other pulse train when nonlinear absorption takes places in the medium. We can easily measure 10-6 absorption changes caused by either two-photon absorption or excited-state absorption with a RF lock-in amplifier. Sepia melanin is studied in detail as a model system. Spectroscopy studies on the instantaneous two-photon absorption (TPA) and the relatively long-lived excited-state absorption (ESA) of melanin are carried out in solution, and imaging capability is demonstrated in B16 cells. It is found that sepia melanin exhibits two distinct excited states with different lifetimes (one at 3 ps, one lasting hundreds of nanoseconds) when pumped at 775 nm. Its characteristic TPA/ESA enables us to image its distribution in cell samples with high resolution comparable to two-photon fluorescence microscopy (TPFM). This new technique could potentially provide valuable information in diagnosing melanoma. © 2007 Society of Photo-Optical Instrumentation Engineers.

Authors
Fu, D; Ye, T; Matthews, TE; Yurtsever, G; Warren, WS
MLA Citation
Fu, D, Ye, T, Matthews, TE, Yurtsever, G, and Warren, WS. "Two-color, two-photon, and excited-state absorption microscopy." Journal of Biomedical Optics 12.5 (2007).
PMID
17994892
Source
scival
Published In
Journal of Biomedical Optics
Volume
12
Issue
5
Publish Date
2007
DOI
10.1117/1.2780173

Two-photon absorption imaging of hemoglobin

We demonstrated that both oxyhemoglobin and deoxyhemoglobin has sequential twophoton absorption properties that can serve as endogenous contrasts in microvasculature imaging. They can also be differentiated through their different excited state dynamics. © 2007 Optical Society of America.

Authors
Fu, D; Matthews, TE; Ye, T; Yurtserver, G; Warren, WS
MLA Citation
Fu, D, Matthews, TE, Ye, T, Yurtserver, G, and Warren, WS. "Two-photon absorption imaging of hemoglobin." Conference on Lasers and Electro-Optics, 2007, CLEO 2007 (2007).
Source
scival
Published In
Conference on Lasers and Electro-Optics, 2007, CLEO 2007
Publish Date
2007
DOI
10.1109/CLEO.2007.4452968

Two-color excited-state absorption imaging of melanins

We have demonstrated a new method for imaging melanin with two-color excited state absorption microscopy. If one of two synchronized mode-locked pulse trains at different colors is intensity modulated, the modulation transfers to the other pulse train when nonlinear absorption takes place in the medium. We can easily measure 10-6 absorption changes caused by either instantaneous two-photon absorption or relatively long lived excited state absorption with a RF lock-in amplifier. Eumelanin and pheomelanin exhibit similar excited state dynamics. However, their difference in excited state absorption and ground state absorption leads to change in the phase of the transient absorption signal. Scanning microscopic imaging is performed with B16 cells, melanoma tissue to demonstrate the 3D high resolution imaging capability. Different melanosome samples are also imaged to illustrate the differences between eumelanin and pheomelanin signals. These differences could enable us to image their respective distribution in tissue samples and provide us with valuable information in diagnosing malignant transformation of melanocytes.

Authors
Fu, D; Ye, T; Matthews, TE; Yurtsever, G; Hong, L; Simon, JD; Warren, WS
MLA Citation
Fu, D, Ye, T, Matthews, TE, Yurtsever, G, Hong, L, Simon, JD, and Warren, WS. "Two-color excited-state absorption imaging of melanins." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 6424 (2007).
Source
scival
Published In
Proceedings of SPIE
Volume
6424
Publish Date
2007
DOI
10.1117/12.698756

Multiphoton femtosecond phase-coherent two-dimensional electronic spectroscopy

In this paper the authors compare 400 nm one-photon and 800 nm two-photon two-dimensional Fourier transform electronic spectra of the organic laser dye Coumarin 102 in methanol using collinear optical pulse sequences and phase cycling. Results from the two different experiments show differences in the photon echo peak positions and shapes, reflecting differences in the two-photon and one-photon selection rules. © 2007 American Institute of Physics.

Authors
Li, C; Wagner, W; Ciocca, M; Warren, WS
MLA Citation
Li, C, Wagner, W, Ciocca, M, and Warren, WS. "Multiphoton femtosecond phase-coherent two-dimensional electronic spectroscopy." Journal of Chemical Physics 126.16 (2007).
PMID
17477602
Source
scival
Published In
Journal of Chemical Physics
Volume
126
Issue
16
Publish Date
2007
DOI
10.1063/1.2721562

Hormone peptide conjugated ironoxide nanoparticles for detection and treatment of metastases

Authors
Leuschner, C; Kumar, C; Warren, W; Hansel, W; Branca, RT; Galiana, G; Hormes, F
MLA Citation
Leuschner, C, Kumar, C, Warren, W, Hansel, W, Branca, RT, Galiana, G, and Hormes, F. "Hormone peptide conjugated ironoxide nanoparticles for detection and treatment of metastases." 2007 NSTI Nanotechnology Conference and Trade Show - NSTI Nanotech 2007, Technical Proceedings 2 (2007): 429-430.
Source
scival
Published In
2007 NSTI Nanotechnology Conference and Trade Show - NSTI Nanotech 2007, Technical Proceedings
Volume
2
Publish Date
2007
Start Page
429
End Page
430

Tissue imaging with shaped femtosecond laser pulses

Authors
Warren, WS; Miller, A; Ye, T; Liu, H; Fischer, MC; Wagner, W
MLA Citation
Warren, WS, Miller, A, Ye, T, Liu, H, Fischer, MC, and Wagner, W. "Tissue imaging with shaped femtosecond laser pulses." 2007.
Source
wos-lite
Published In
Springer Series in Chemical Physics
Volume
88
Publish Date
2007
Start Page
807
End Page
+

Deep tissue imaging with shaped femtosecond laser pulses

Two-photon absorption and self phase modulation can be detected deep in tissue with modest laser powers, using shaped femtosecond pulses. This permit microscopic-resolution images of biologically important targets. © 2006 Optical Society of America.

Authors
Warren, WS; Ye, T; Fischer, M; Yurtsever, G; Li, C; Liu, H; Fu, D
MLA Citation
Warren, WS, Ye, T, Fischer, M, Yurtsever, G, Li, C, Liu, H, and Fu, D. "Deep tissue imaging with shaped femtosecond laser pulses." Optics InfoBase Conference Papers (January 1, 2006).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2006

Two-photon absorption of oxyhemoglobin and methemoglogin for microscopic imaging

We measured two-photon absorption of oxyhemoglobin and methemoglobin with modest laser powers. In combination with our previous work on melanin tissue imaging, this shows two-photon absorption imaging of hemoglobin state is feasible. © 2005 Optical Society of America.

Authors
Yurtsever, G; Weaver, K; Ye, T; Warren, WS
MLA Citation
Yurtsever, G, Weaver, K, Ye, T, and Warren, WS. "Two-photon absorption of oxyhemoglobin and methemoglogin for microscopic imaging." Optics InfoBase Conference Papers (January 1, 2006).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2006

Stimulated Raman scattering with shaped femtosecond pulses

Authors
Sariyanni, ZE; Rostovtsev, YV; Warren, WS; Scully, MO
MLA Citation
Sariyanni, ZE, Rostovtsev, YV, Warren, WS, and Scully, MO. "Stimulated Raman scattering with shaped femtosecond pulses." Optics InfoBase Conference Papers (January 1, 2006).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2006

Coherent and stimulated Raman spectroscopy with shaped femtosecond pulses in scattering media

We show that femtosecond shaped pulses can be used to detect coherent and stimulated Raman scattering in multi-scattering media. It is possible to perform Raman spectroscopy with such specially shaped pulses to determine vibrational frequencies and relaxation rates. The technique can be applied to spore detection and tissue microscopy. © 2006 Optical Society of America.

Authors
Rostovtsev, YV; Sariyanni, ZE; Warren, WS; Scully, MO
MLA Citation
Rostovtsev, YV, Sariyanni, ZE, Warren, WS, and Scully, MO. "Coherent and stimulated Raman spectroscopy with shaped femtosecond pulses in scattering media." Optics InfoBase Conference Papers (January 1, 2006).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2006

Coherent and stimulated Raman spectroscopy with shaped femtosecond pulses in scattering media

We show that femtosecond shaped pulses can be used to detect coherent and stimulated Raman scattering in multi-scattering media. It is possible to perform Raman spectroscopy with such specially shaped pulses to determine vibrational frequencies and relaxation rates. The technique can be applied to spore detection and tissue microscopy. © 2006 Optical Society of America.

Authors
Rostovtsev, YV; Sariyanni, ZE; Warren, WS; Scully, MO
MLA Citation
Rostovtsev, YV, Sariyanni, ZE, Warren, WS, and Scully, MO. "Coherent and stimulated Raman spectroscopy with shaped femtosecond pulses in scattering media." Optics InfoBase Conference Papers (January 1, 2006).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2006

Coherent and stimulated raman spectroscopy with shaped femtosecond pulses in scattering media

We show that femtosecond shaped pulses can be used to detect coherent and stimulated Raman scattering in multi-scattering media. It is possible to perform Raman spectroscopy with such specially shaped pulses to determine vibrational frequencies and relaxation rates. The technique can be applied to spore detection and tissue microscopy. © 2006 Optical Society of America.

Authors
Rostovtsev, YV; Sariyanni, ZE; Warren, WS; Scully, MO
MLA Citation
Rostovtsev, YV, Sariyanni, ZE, Warren, WS, and Scully, MO. "Coherent and stimulated raman spectroscopy with shaped femtosecond pulses in scattering media." Optics InfoBase Conference Papers (January 1, 2006).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2006

Coherent and stimulated Raman spectroscopy with shaped femtosecond pulses in scattering media

We show that femtosecond shaped pulses can be used to detect coherent and stimulated Raman scattering in multi-scattering media. It is possible to perform Raman spectroscopy with such specially shaped pulses to determine vibrational frequencies and relaxation rates. The technique can be applied to spore detection and tissue microscopy. © 2006 Optical Society of America.

Authors
Rostovtsev, YV; Sariyanni, ZE; Warren, WS; Scully, MO
MLA Citation
Rostovtsev, YV, Sariyanni, ZE, Warren, WS, and Scully, MO. "Coherent and stimulated Raman spectroscopy with shaped femtosecond pulses in scattering media." Optics InfoBase Conference Papers (January 1, 2006).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2006

Two-photon absorption microscopy of tissue

Two-photon absorption microscopy (TPAM) has been demonstrated to be able to image melanin with high sensitivity. TPAM opens up a wide range of nonfluorescent molecular targets. © 2005 Optical Society of America.

Authors
Ye, T; Fischer, M; Yurtsever, G; Warren, WS
MLA Citation
Ye, T, Fischer, M, Yurtsever, G, and Warren, WS. "Two-photon absorption microscopy of tissue." Optics InfoBase Conference Papers (January 1, 2006).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2006

Determining thickness independently from optical constants using ultrafast spectral interferometry

We show that the application of ultrafast techniques, specially femtosecond lasers, allow simultaneous measurements of material thickness and optical constants from transmission measurements using a frequency interferometer. © 2005 Optical Society of America.

Authors
Huang, F; Federici, JF; Gary, D; Jedju, T; Warren, WS
MLA Citation
Huang, F, Federici, JF, Gary, D, Jedju, T, and Warren, WS. "Determining thickness independently from optical constants using ultrafast spectral interferometry." Optics InfoBase Conference Papers (January 1, 2006).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2006

All-UV time-resolved CARS

Time-resolved, coherent anti-Stokes Raman scattering from internal vibrations in calcite is reported with all the wavelengths in the ultraviolet. Two-photon absorption, excitation-dependent dephasing times, and a comparison of ultraviolet and visible efficiencies are described. © 2005 Optical Society of America.

Authors
Mehendale, M; Giordmaine, JA; Gatzogiannis, E; Dogariu, A; Beadie, G; Warren, WS; Scully, MO
MLA Citation
Mehendale, M, Giordmaine, JA, Gatzogiannis, E, Dogariu, A, Beadie, G, Warren, WS, and Scully, MO. "All-UV time-resolved CARS." Optics InfoBase Conference Papers (January 1, 2006).
Source
scopus
Published In
Optics InfoBase Conference Papers
Publish Date
2006

Imaging melanin by two-photon absorption microscopy

Multiphoton excitation fluorescence microscopy has proven to be a powerful method for non-invasive, in vivo, thick tissue imaging with molecular specificity. However, many important endogenous biomolecules do not fluoresce (NAD) or fluoresce with low efficiency (Melanin). In this report femtosecond pulse shaping methods are used to measure two-photon absorption (TPA) directly with very high sensitivity. Combining with the laser scanning microscope, this Two-photon Absorption Microscopy (TPAM) retains the penetration and localization advantages of two-photon fluorescence microscopy and permits direct observation of important endogenous molecular markers (melanin or hemoglobin) which are invisible in multiphoton fluorescence microscopy. We have demonstrated here for the first time that TPAM can successfully and more efficiently image melanoma cells and tissues and provide a good melanin contrast in optical sectioning of the melanoma lesions which are comparable to pathological histology. Combining with the two-photon fluorescence images acquired simultaneously, the distribution patterns of the melanocytes and their intratissue behavior could be studied without cutting the lesions from patients. TPAM will undoubtedly find the applications in the clinical diagnosis and biomedical research.

Authors
Ye, T; Yurtsever, G; Fischer, M; Simon, JD; Warren, WS
MLA Citation
Ye, T, Yurtsever, G, Fischer, M, Simon, JD, and Warren, WS. "Imaging melanin by two-photon absorption microscopy." Proceedings of SPIE - The International Society for Optical Engineering 6089 (2006).
Source
scival
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
6089
Publish Date
2006
DOI
10.1117/12.646139

Spectroscopy: Shifting light with spin

NMR spectroscopy has changed enormously over the years, but signal detection has stayed the same since the technique was invented. The latest thinking literally shines a new light on things. ©2006 Nature Publishing Group.

Authors
Warren, WS
MLA Citation
Warren, WS. "Spectroscopy: Shifting light with spin." Nature 442.7106 (2006): 990--.
PMID
16943825
Source
scival
Published In
Nature
Volume
442
Issue
7106
Publish Date
2006
Start Page
990-
DOI
10.1038/442990a

Coherence, correlation and entanglement: Have we learned anything from NMR quantum computing?

Nearly a decades' worth of experimental efforts on solution NMR quantum computing have confirmed that such systems will not be scalable to a useful number of qubits, completely consistent with quantum mechanical predictions in 1997. However, the theoretical framework has led to new insights into the nature of coherence, correlation, and entanglement, and may ultimately help enable other magnetic resonance applications. © 2006 American Institute of Physics.

Authors
Warren, WS
MLA Citation
Warren, WS. "Coherence, correlation and entanglement: Have we learned anything from NMR quantum computing?." AIP Conference Proceedings 864 (2006): 324-330.
Source
scival
Published In
AIP Conference Proceedings
Volume
864
Publish Date
2006
Start Page
324
End Page
330
DOI
10.1063/1.2400903

All-ultraviolet time-resolved coherent anti-Stokes Raman scattering

We report all-UV coherent anti-Stokes Raman scattering (CARS) in calcite with 250-280 nm pump, Stokes, probe, and anti-Stokes light. UV CARS efficiency is ∼7X higher than for comparable scattering in the visible, 480-540 nm. Time-resolved UV CARS reveals lengthening of the dephasing time of 1086 cm -1 CO32- internal vibrations from 4 to 7 ps with increasing vibrational excitation, consistent with a phonon depletion model. © 2006 Optical Society of America.

Authors
Mehendale, M; Giordmaine, JA; Gatzogiannis, E; Dogariu, A; Warren, WS; Beadie, G; Scully, MO
MLA Citation
Mehendale, M, Giordmaine, JA, Gatzogiannis, E, Dogariu, A, Warren, WS, Beadie, G, and Scully, MO. "All-ultraviolet time-resolved coherent anti-Stokes Raman scattering." Optics Letters 31.2 (2006): 256-258.
Source
scival
Published In
Optics Letters
Volume
31
Issue
2
Publish Date
2006
Start Page
256
End Page
258
DOI
10.1364/OL.31.000256

Stimulated Raman scattering with shaped femtosecond pulses

We show that spectral hole refilling can be used to detect stimulated Raman scattering to determine vibrational frequency of molecules. The technique can be applied to spore detection and tissue microscopy. © 2005 Optical Society of America.

Authors
Sariyanni, ZE; Rostovtsev, YV; Warren, WS; Scully, MO
MLA Citation
Sariyanni, ZE, Rostovtsev, YV, Warren, WS, and Scully, MO. "Stimulated Raman scattering with shaped femtosecond pulses." Conference on Lasers and Electro-Optics and 2006 Quantum Electronics and Laser Science Conference, CLEO/QELS 2006 (2006).
Source
scival
Published In
Conference on Lasers and Electro-Optics and 2006 Quantum Electronics and Laser Science Conference, CLEO/QELS 2006
Publish Date
2006
DOI
10.1109/CLEO.2006.4628895

Two-photon absorption and self-phase modulation measurements with shaped femtosecond laser pulses

We demonstrate experimentally that phase sensitive detection of spectral hole refilling can yield information about self-phase modulation and two-photon absorption coefficients. © 2005 Optical Society of America.

Authors
Fischer, MC; Ye, T; Yurtsever, G; Miller, A; Ciocca, M; Wagner, W; Warren, WS
MLA Citation
Fischer, MC, Ye, T, Yurtsever, G, Miller, A, Ciocca, M, Wagner, W, and Warren, WS. "Two-photon absorption and self-phase modulation measurements with shaped femtosecond laser pulses." 2005 Conference on Lasers and Electro-Optics, CLEO 2 (December 1, 2005): 968-970.
Source
scopus
Published In
2005 Conference on Lasers and Electro-Optics, CLEO
Volume
2
Publish Date
2005
Start Page
968
End Page
970

Two-photon absorption microscopy of tissue

Two-photon absorption microscopy (TPAM) has been demonstrated to be able to image melanin with high sensitivity. TPAM opens up a wide range of nonfluorescent molecular targets. © 2005 Optical Society of America.

Authors
Ye, T; Fischer, M; Yurtsever, G; Warren, WS
MLA Citation
Ye, T, Fischer, M, Yurtsever, G, and Warren, WS. "Two-photon absorption microscopy of tissue." 2005 Conference on Lasers and Electro-Optics, CLEO 2 (December 1, 2005): 1512-1514.
Source
scopus
Published In
2005 Conference on Lasers and Electro-Optics, CLEO
Volume
2
Publish Date
2005
Start Page
1512
End Page
1514

Determining thickness independently from optical constants using ultrafast spectral interferometry

We show that the application of ultrafast techniques, specially femtosecond lasers, allow simultaneous measurements of material thickness and optical constants from transmission measurements using a frequency interferometer. © 2005 Optical Society of America.

Authors
Huang, F; Federici, JF; Gary, D; Jedju, T; Warren, WS
MLA Citation
Huang, F, Federici, JF, Gary, D, Jedju, T, and Warren, WS. "Determining thickness independently from optical constants using ultrafast spectral interferometry." 2005 Conference on Lasers and Electro-Optics, CLEO 2 (December 1, 2005): 1103-1105.
Source
scopus
Published In
2005 Conference on Lasers and Electro-Optics, CLEO
Volume
2
Publish Date
2005
Start Page
1103
End Page
1105

All-UV time-resolved CARS

Time-resolved, coherent anti-Stokes Raman scattering from internal vibrations in calcite is reported with all the wavelengths in the ultraviolet. Two-photon absorption, excitation-dependent dephasing times, and a comparison of ultraviolet and visible efficiencies are described. © 2005 Optical Society of America.

Authors
Mehendale, M; Giordmaine, JA; Gatzogiannis, E; Dogariu, A; Beadie, G; Warren, WS; Scully, MO
MLA Citation
Mehendale, M, Giordmaine, JA, Gatzogiannis, E, Dogariu, A, Beadie, G, Warren, WS, and Scully, MO. "All-UV time-resolved CARS." 2005 Conference on Lasers and Electro-Optics, CLEO 1 (December 1, 2005): 363-365.
Source
scopus
Published In
2005 Conference on Lasers and Electro-Optics, CLEO
Volume
1
Publish Date
2005
Start Page
363
End Page
365

Two-photon absorption and self-phase modulation measurements with shaped femtosecond laser pulses

We demonstrate experimentally that phase sensitive detection of spectral hole refilling can yield information about self-phase modulation and two-photon absorption coefficients. © 2005 Optical Society of America.

Authors
Fischer, MC; Ye, T; Yurtsever, G; Miller, A; Ciocca, M; Wagner, W; Warren, WS
MLA Citation
Fischer, MC, Ye, T, Yurtsever, G, Miller, A, Ciocca, M, Wagner, W, and Warren, WS. "Two-photon absorption and self-phase modulation measurements with shaped femtosecond laser pulses." Optics InfoBase Conference Papers (2005).
Source
scival
Published In
Optics InfoBase Conference Papers
Publish Date
2005

"Simultaneous measurement of two-photon absorption and self-phase modulation by femtosecond pulse shaping"

Authors
Miller, A; Fischer, M; Warren, WS
MLA Citation
Miller, A, Fischer, M, and Warren, WS. ""Simultaneous measurement of two-photon absorption and self-phase modulation by femtosecond pulse shaping" (Submitted)." Optics Letters (2005). (Academic Article)
Source
manual
Published In
Optics Letters
Publish Date
2005

"Probing structural anisotropy in heterogeneous media via indirect measurements of the dipole-dipole interaction between solid and liquid phases"

Authors
Bouchard, L-S; Chin, C-L; Wehrli, FW; Warren, WS
MLA Citation
Bouchard, L-S, Chin, C-L, Wehrli, FW, and Warren, WS. ""Probing structural anisotropy in heterogeneous media via indirect measurements of the dipole-dipole interaction between solid and liquid phases" (Submitted)." Phys. Rev. B. (2005). (Academic Article)
Source
manual
Published In
Phys. Rev. B.
Publish Date
2005

Multiple-quantum vector field imaging by magnetic resonance

Authors
Bouchard, L-S; Warren, WS
MLA Citation
Bouchard, L-S, and Warren, WS. "Multiple-quantum vector field imaging by magnetic resonance (Accepted)." J. Magn. Reson. 176 (2005): xx-. (Academic Article)
PMID
16087374
Source
manual
Published In
J. Magn. Reson.
Volume
176
Publish Date
2005
Start Page
xx

"Rapid phase-cycled two dimensional optical spectroscopy in flourescence and transmission mode"

Authors
Wagner, W; Li, C; Semmlow, J; Warren, WS
MLA Citation
Wagner, W, Li, C, Semmlow, J, and Warren, WS. ""Rapid phase-cycled two dimensional optical spectroscopy in flourescence and transmission mode"." Optics Express 13.10 (2005): 2697-3706. (Academic Article)
Source
manual
Published In
Optics Express
Volume
13
Issue
10
Publish Date
2005
Start Page
2697
End Page
3706

Structural anisotropy and internal magnetic fields in trabecular bone: Coupling solution and solid dipolar interactions

We investigate the use of intermolecular multiple-quantum coherence to probe structural anisotropy in trabecular bone. Despite the low volume fraction of bone, the bone-water interface produces internal magnetic field gradients which modulate the dipolar field, depending on sample orientation, choice of dipolar correlation length, correlation gradient direction, and evolution time. For this system, the probing of internal magnetic field gradients in the liquid phase permits indirect measurements of the solid phase dipolar field. Our results suggest that measurements of volume-averaged signal intensity as a function of gradient strength and three orthogonal directions could be used to non-invasively measure the orientation of structures inside a sample or their degree of anisotropy. The system is modeled as having two phases, solid and liquid (bone and water), which differ in their magnetization density and magnetic susceptibility. A simple calculation using a priori knowledge of the material geometry and distribution of internal magnetic fields verifies the experimental measurements as a function of gradient strength, direction, and sample orientation. © 2005 Elsevier Inc. All rights reserved.

Authors
Bouchard, L-S; Wehrli, FW; Chin, C-L; Warren, WS
MLA Citation
Bouchard, L-S, Wehrli, FW, Chin, C-L, and Warren, WS. "Structural anisotropy and internal magnetic fields in trabecular bone: Coupling solution and solid dipolar interactions." Journal of Magnetic Resonance 176.1 (2005): 27-36.
PMID
15953742
Source
scival
Published In
Journal of Magnetic Resonance
Volume
176
Issue
1
Publish Date
2005
Start Page
27
End Page
36
DOI
10.1016/j.jmr.2005.05.012

"Exploring permeation in blookd by its internal magnetic field"

Authors
Lisitza, N; Song, Y-Q; Warren, WS
MLA Citation
Lisitza, N, Song, Y-Q, and Warren, WS. ""Exploring permeation in blookd by its internal magnetic field" (Submitted)." Proc. Natl. Acad. Sci. (2005). (Academic Article)
Source
manual
Published In
Proc. Natl. Acad. Sci.
Publish Date
2005

Two-photon absorption and self-phase modulation measurements with shaped femtosecond laser pulses

We show that phase-sensitive detection of spectral hole refilling can yield information about self-phase modulation and two-photon absorption coefficients. We expect that, when applied to tissue microscopy, this technique will allow the study of endogenous molecular markers beneath the surface, even if those markers are nonfluorescent. © 2005 Optical Society of America.

Authors
Fischer, MC; Ye, T; Yurtsever, G; Miller, A; Ciocca, M; Wagner, W; Warren, WS
MLA Citation
Fischer, MC, Ye, T, Yurtsever, G, Miller, A, Ciocca, M, Wagner, W, and Warren, WS. "Two-photon absorption and self-phase modulation measurements with shaped femtosecond laser pulses." Optics Letters 30.12 (2005): 1551-1553.
PMID
16007804
Source
scival
Published In
Optics Letters
Volume
30
Issue
12
Publish Date
2005
Start Page
1551
End Page
1553
DOI
10.1364/OL.30.001551

Two-photon absorption microscopy of tissue

Two-photon absorption microscopy (TPAM) has been demonstrated to be able to image melanin with high sensitivity. TPAM opens up a wide range of nonfluorescent molecular targets. © 2005 Optical Society of America.

Authors
Ye, T; Fischer, M; Yurtsever, G; Warren, WS
MLA Citation
Ye, T, Fischer, M, Yurtsever, G, and Warren, WS. "Two-photon absorption microscopy of tissue." 2005 Conference on Lasers and Electro-Optics, CLEO 2 (2005): 1512-1514.
Source
scival
Published In
2005 Conference on Lasers and Electro-Optics, CLEO
Volume
2
Publish Date
2005
Start Page
1512
End Page
1514

Two-photon absorption and self-phase modulation measurements with shaped femtosecond laser pulses

We demonstrate experimentally that phase sensitive detection of spectral hole refilling can yield information about self-phase modulation and two-photon absorption coefficients. © 2005 Optical Society of America.

Authors
Fischer, MC; Ye, T; Yurtsever, G; Miller, A; Ciocca, M; Wagner, W; Warren, WS
MLA Citation
Fischer, MC, Ye, T, Yurtsever, G, Miller, A, Ciocca, M, Wagner, W, and Warren, WS. "Two-photon absorption and self-phase modulation measurements with shaped femtosecond laser pulses." 2005 Conference on Lasers and Electro-Optics, CLEO 2 (2005): 968-970.
Source
scival
Published In
2005 Conference on Lasers and Electro-Optics, CLEO
Volume
2
Publish Date
2005
Start Page
968
End Page
970

Ultrafast intermolecular zero quantum spectroscopy

Clinical magnetic resonance spectroscopy is typically limited by magnetic inhomogeneities which destroy spectral resolution, but intermolecular zero quantum coherences (iZQCs) are insensitive to such inhomogeneities. iZQC resolution in vivo, however, has been hampered by physiological fluctuations over the time scale of the two-dimensional acquisition. A faster iZQC sequence will allow us to average away these fluctuations, and thus we present a new approach to ultrafast two-dimensional spectroscopy. This communication reports iZQC experiments acquiring up to 31 t1-points per scan, as well as extensions to a broad range of other 2D sequences. Copyright © 2005 American Chemical Society.

Authors
Galiana, G; Branca, RT; Warren, WS
MLA Citation
Galiana, G, Branca, RT, and Warren, WS. "Ultrafast intermolecular zero quantum spectroscopy." Journal of the American Chemical Society 127.50 (2005): 17574-17575.
PMID
16351065
Source
scival
Published In
Journal of the American Chemical Society
Volume
127
Issue
50
Publish Date
2005
Start Page
17574
End Page
17575
DOI
10.1021/ja054463m

Gain-swept superradiance applied to the stand-off detection of trace impurities in the atmosphere

We show that gain-swept superradiance can be used to detect low (parts per million) concentrations of various gases at distances on the order of kilometers, which is done by using pulse timing to create small regions of gain at positions that sweep toward a detector. The technique is far more sensitive than previous methods such as light detection and ranging or differential absorption light detection and ranging. © 2005 by The National Academy of Sciences of the USA.

Authors
Kocharovsky, V; Cameron, S; Lehmann, K; Lucht, R; Miles, R; Rostovtsev, Y; Warren, W; Welch, GR; Scully, MO
MLA Citation
Kocharovsky, V, Cameron, S, Lehmann, K, Lucht, R, Miles, R, Rostovtsev, Y, Warren, W, Welch, GR, and Scully, MO. "Gain-swept superradiance applied to the stand-off detection of trace impurities in the atmosphere." Proceedings of the National Academy of Sciences of the United States of America 102.22 (2005): 7806-7811.
Source
scival
Published In
Proceedings of the National Academy of Sciences of the United States of America
Volume
102
Issue
22
Publish Date
2005
Start Page
7806
End Page
7811
DOI
10.1073/pnas.0500534102

Mitochondrial NADH as the bellwether of tissue O2 delivery

It is proposed that the redox state of mitochondrial NADH1 will complement blood gas analysis for measuring the health and welfare of human tissues. Use of arterial oxygen saturation levels (SaO2), especially as assayed by the Nellcor instrument, has spread almost everywhere in medicine despite the fact that hypoxia of internal organs, liver, kidney, brain, pancreas, etc. is not well indicated by peripheral digital oxygenation. Indeed, there is an implied liability in the failure to infer central oxygenation from peripheral values. Near infrared (NIR) sensing of deep tissue saturation of hemoglobin (StO2) requires multi-wavelength, multi-site measurement of both absorption and scattering properties by time or frequency domain NIR methods. Corrections for underlying water and lipid absorptions can be made so that the correct value for, and saturation oh hemoglobin are obtained. Nevertheless, the significance of blood oxygen saturation, even localized to particular organs, can be questioned from the standpoint of what is the critical value of the desaturation from which the tissue can recover2; for example, in the case of cortical neurons where stroke, compression ischemia, etc. cause O2 lack, this value becomes of significant clinical importance in both the brain and the spinal chord. These approaches are actively pursued and the possibility of subsurface redox state measurement in human tissues may eventually emerge as the quantitative metric of tissue metabolic state and of hypoxic stress. The great flexibility and versatility of the fast, economical and "tetherless" nature of opto-electronic technology is appropriate to the manifold challenges of neuronal function as currently measured by intrinsic signals and soon to be studiable by extrinsic signals of metabolism and electrophysiological functions.

Authors
Chance, B; Nioka, S; Warren, W; Yurtsever, G
MLA Citation
Chance, B, Nioka, S, Warren, W, and Yurtsever, G. "Mitochondrial NADH as the bellwether of tissue O2 delivery." Advances in Experimental Medicine and Biology 566 (2005): 231-242.
PMID
16594157
Source
scival
Published In
Advances in experimental medicine and biology
Volume
566
Publish Date
2005
Start Page
231
End Page
242
DOI
10.1007/0-387-26206-7_31

Rapid phase-cycled two-dimensional optical spectroscopy in fluorescence and transmission mode

Two dimensional magnetic and optical spectra contain information about structure and dynamics inaccessible to the linear spectroscopist. Recently, phase cycling techniques in optical spectroscopy have extended the capabilities of two-dimensional electronic spectroscopy. Here, we present a method to generate collinear pump/probe pulses at high update rates for two-dimensional electronic spectroscopy. Both fluorescence mode and transmission mode photon echo data from rubidium vapor is presented. © 2005 Optical Society of America.

Authors
Wagner, W; Li, C; Semmlow, J; Warren, WS
MLA Citation
Wagner, W, Li, C, Semmlow, J, and Warren, WS. "Rapid phase-cycled two-dimensional optical spectroscopy in fluorescence and transmission mode." Optics Express 13.10 (2005): 3697-3706.
Source
scival
Published In
Optics express
Volume
13
Issue
10
Publish Date
2005
Start Page
3697
End Page
3706
DOI
10.1364/OPEX.13.003697

Determining thickness independently from optical constants using ultrafast spectral interferometry

We show that the application of ultrafast techniques, specially femtosecond lasers, allow simultaneous measurements of material thickness and optical constants from transmission measurements using a frequency interferometer. © 2005 Optical Society of America.

Authors
Huang, F; Federici, JF; Gary, D; Jedju, T; Warren, WS
MLA Citation
Huang, F, Federici, JF, Gary, D, Jedju, T, and Warren, WS. "Determining thickness independently from optical constants using ultrafast spectral interferometry." 2005 Conference on Lasers and Electro-Optics, CLEO 2 (2005): 1103-1105.
Source
scival
Published In
2005 Conference on Lasers and Electro-Optics, CLEO
Volume
2
Publish Date
2005
Start Page
1103
End Page
1105

All-UV time-resolved CARS

Time-resolved, coherent anti-Stokes Raman scattering from internal vibrations in calcite is reported with all the wavelengths in the ultraviolet. Two-photon absorption, excitation-dependent dephasing times, and a comparison of ultraviolet and visible efficiencies are described. © 2005 Optical Society of America.

Authors
Mehendale, M; Giordmaine, JA; Gatzogiannis, E; Dogariu, A; Beadie, G; Warren, WS; Scully, MO
MLA Citation
Mehendale, M, Giordmaine, JA, Gatzogiannis, E, Dogariu, A, Beadie, G, Warren, WS, and Scully, MO. "All-UV time-resolved CARS." 2005 Conference on Lasers and Electro-Optics, CLEO 1 (2005): 363-365.
Source
scival
Published In
2005 Conference on Lasers and Electro-Optics, CLEO
Volume
1
Publish Date
2005
Start Page
363
End Page
365

"Simultaneous Acquistion of Multiple Orders of Intermolecular Multiple- Quantum Coherence Images in Vivo"

Authors
Shannon, KL; Branca, RT; Galiana, G; Cenzano, S; Soboyevo, W; Warren, WS
MLA Citation
Shannon, KL, Branca, RT, Galiana, G, Cenzano, S, Soboyevo, W, and Warren, WS. ""Simultaneous Acquistion of Multiple Orders of Intermolecular Multiple- Quantum Coherence Images in Vivo"." Magnetic Resonanace Imaging 22.10 (December 2004): 1407-1412. (Academic Article)
Source
manual
Published In
Magnetic Resonanace Imaging
Volume
22
Issue
10
Publish Date
2004
Start Page
1407
End Page
1412

Tensorial character of magnetization diffusion in periodic lattices

Averaged Bloch equations for magnetization evolution in a biphasic heterogeneous material with periodic structures are derived using a two-scale asymptotic expansion. Upscaling of the partial differential equations with microscopic boundary conditions results in equations of motion for the magnetization vector that are functionally similar to the Bloch equations, but without microscopic boundaries, and with a tensorial term describing effective diffusion behavior. In the process we obtain a prescription for calculating individual components of the diffusion tensor by solving an auxiliary boundary-valued problem on the microscopic unit cell. This allows, in particular, numerical calculations of the diffusion tensor for arbitrary geometries of the unit cellin a reasonable computing time.

Authors
Bouchard, L-S; Warren, WS
MLA Citation
Bouchard, L-S, and Warren, WS. "Tensorial character of magnetization diffusion in periodic lattices." Physical Review B - Condensed Matter and Materials Physics 70.22 (2004): 224426-1-224426-9-.
Source
scival
Published In
Physical Review B - Condensed Matter and Materials Physics
Volume
70
Issue
22
Publish Date
2004
Start Page
224426-1-224426-9
DOI
10.1103/PhysRevB.70.224426

Observing Bragg-like diffraction via multiple coupled nuclear spins

Using intermolecular multiple-quantum coherence (iMQC) we report the first observation of Bragg-like diffraction via multiple distantly coupled nuclear spins. A compact quantum-mechanical formalism has been developed for analytically calculating iMQCs. The diffraction of iMQCs of various orders has been studied in a two-dimensional array structure. It indicates that phase cycling and flip angle selection are crucial for accurately measuring iMQC and the specific iMQCs measured in previous studies were likely contaminated by undesired coherences. We have also examined the capability and the current limitation of applying iMQCs for structural studies. The observation of iMQC diffraction introduces a new method for studying collective dynamics. © 2004 Elsevier B.V. All rights reserved.

Authors
Tang, X-P; Chin, C-L; Bouchard, L-S; Wehrli, FW; Warren, WS
MLA Citation
Tang, X-P, Chin, C-L, Bouchard, L-S, Wehrli, FW, and Warren, WS. "Observing Bragg-like diffraction via multiple coupled nuclear spins." Physics Letters, Section A: General, Atomic and Solid State Physics 326.1-2 (2004): 114-125.
Source
scival
Published In
Physics Letters, Section A: General, Atomic and Solid State Physics
Volume
326
Issue
1-2
Publish Date
2004
Start Page
114
End Page
125
DOI
10.1016/j.physleta.2004.04.017

Signal irreproducibility in high-field solution magnetic resonance experiments caused by spin turbulence

The turbulent spin dynamics resulting from the joint action of radiation damping and distant dipolar field caused signal irreversibility in gradient based magnetic resonance experiments. The experiments for the stimulated echo variant were carried out which emphasize the generality of observed signal irreproducibility. The modulated magnetization was perturbed to render magic-angle gradients ineffective in supressing signal fluctuations. The results show that the magic-angle gradients may not completely curb unstable modes of growth leading to turbulent spin motion.

Authors
Huang, SY; Walls, JD; Wang, Y; Warren, WS; Lin, Y-Y
MLA Citation
Huang, SY, Walls, JD, Wang, Y, Warren, WS, and Lin, Y-Y. "Signal irreproducibility in high-field solution magnetic resonance experiments caused by spin turbulence." Journal of Chemical Physics 121.13 (2004): 6105-6109.
PMID
15446904
Source
scival
Published In
Journal of Chemical Physics
Volume
121
Issue
13
Publish Date
2004
Start Page
6105
End Page
6109
DOI
10.1063/1.1802492

Reconstruction of porous material geometry by stochastic optimization based on bulk NMR measurements of the dipolar field

The dependence of the bulk signal intensity from a CRAZED NMR pulse sequence on magnetic field gradient strength and direction as a method to probe the geometry of porous materials is investigated. In this article, we report on the reconstruction of three-dimensional media consisting of a void phase and an NMR-observable liquid phase using the bulk intensity of the distant dipolar field. The correlation gradient strength and direction provide the spatial encoding of the material geometry. An integral equation for the total signal intensity is then solved numerically by a simulated annealing algorithm to recover the indicator function of the fluid phase. Results show that cylindrical and spherical structures smaller than the volume contributing to the NMR signal can be resolved using three values of the correlation distance and three orthogonal gradient directions. This is done by minimizing a cost function which measures the distance between the bulk signal dependence on gradient parameters for the simulated configuration and the signal dependence for the target configuration. The algorithm can reconstruct and differentiate their spherical and cylindrical phase-inverted equivalents. It can also differentiate horizontal from vertical cylinders, demonstrating the potential for assessing structural anisotropy and other coarse geometric quantifiers in a porous material. © 2004 Published by Elsevier Inc.

Authors
Bouchard, L-S; Warren, WS
MLA Citation
Bouchard, L-S, and Warren, WS. "Reconstruction of porous material geometry by stochastic optimization based on bulk NMR measurements of the dipolar field." Journal of Magnetic Resonance 170.2 (2004): 299-309.
PMID
15388094
Source
scival
Published In
Journal of Magnetic Resonance
Volume
170
Issue
2
Publish Date
2004
Start Page
299
End Page
309
DOI
10.1016/j.jmr.2004.05.023

Propagation effects on the peak profile in two-dimensional optical photon echo spectroscopy

The effect of pulse propagation on the lineshape in a two-dimensional photon echo spectrum is investigated using the coupled Maxwell Bloch equations. Reshaping of excitation and signal pulses due to propagation results in broadening of peak profiles. The amount of broadening is not symmetric along the two dimensions and depends on pulse intensity and relaxation mechanism. It is found that relaxation mechanisms that give the same lineshape at low optical density (OD) can give different lineshapes at high OD. Even at relatively low OD the reshaping can be quite severe, and might result in misinterpretation of the obtained spectrum. © 2003 Published by Elsevier B.V.

Authors
Keusters, D; Warren, WS
MLA Citation
Keusters, D, and Warren, WS. "Propagation effects on the peak profile in two-dimensional optical photon echo spectroscopy." Chemical Physics Letters 383.1-2 (2004): 21-24.
Source
scival
Published In
Chemical Physics Letters
Volume
383
Issue
1-2
Publish Date
2004
Start Page
21
End Page
24
DOI
10.1016/j.cplett.2003.10.130

Two-photon absorption imaging with shaped femtosecond laser pulses

Femtosecond laser pulse shaping permits background-free detection of two-photon absorption, which tends to refill spectral holes. This opens up new spectroscopic windows for monitoring tissue characteristics.

Authors
Warren, WS; Miller, A; Wagner, W; Ye, T; Fischer, M; Yurtsever, G
MLA Citation
Warren, WS, Miller, A, Wagner, W, Ye, T, Fischer, M, and Yurtsever, G. "Two-photon absorption imaging with shaped femtosecond laser pulses." Springer Series in Chemical Physics 79 (2004): 867-869.
Source
scival
Published In
Springer Series in Chemical Physics
Volume
79
Publish Date
2004
Start Page
867
End Page
869

Deep tissue imaging approaches by direct capture of two-photon absorption

Multiphoton imaging with fluorescence detection has proven to be a powerful method for moderately deep tissue imaging (less than 1 mm) with molecular specificity. However, many important endogenous biomolecules do not fluoresce (NAD) or with low efficiency (Melanin). In this paper two femtosecond pulse shaping methods have been demonstrated to detect two-photon absorption (TPA), instead of fluorescence, with high sensitivity, which opens up a wide range of molecular targets. It also facilitates longer excitation wavelengths, which permit greater tissue penetration. Developing the imaging system by using these new methods will be also discussed. © 2004 IEEE.

Authors
Ye, T; Wagner, W; Tian, P; Yurtsever, G; Fischer, M; Warren, WS
MLA Citation
Ye, T, Wagner, W, Tian, P, Yurtsever, G, Fischer, M, and Warren, WS. "Deep tissue imaging approaches by direct capture of two-photon absorption." 2004 2nd IEEE International Symposium on Biomedical Imaging: Macro to Nano 1 (2004): 668-671.
Source
scival
Published In
2004 2nd IEEE International Symposium on Biomedical Imaging: Macro to Nano
Volume
1
Publish Date
2004
Start Page
668
End Page
671

Simultaneous acquisition of multiple orders of intermolecular multiple-quantum coherence images in vivo

Until recently, NMR imaging with intermolecular multiple-quantum coherences (iMQCs) has been based on the acquisition of a single echo. In vivo studies of iMQC image contrast would greatly benefit from a method that could acquire several orders of quantum coherence during the same acquisition. This would enable comparison of the image contrast for various orders and eliminate image coregistration problems between scans. It has previously been demonstrated that multiple orders of iMQC images can be simultaneously acquired of a simple phantom. Here, we examine the technique and its effect on biological tissue, both in vivo and in vitro. First, we establish the effectiveness of the iMQC sequence in vivo using earthworms as specimens. We then further show that the multi-CRAZED sequence enhances detection of next generation (nanoparticle) contrast agents on excised tumor tissue. © 2004 Elsevier Inc. All rights reserved.

Authors
Shannon, KL; Branca, RT; Galiana, G; Cenzano, S; Bouchard, L-S; Soboyejo, W; Warren, WS
MLA Citation
Shannon, KL, Branca, RT, Galiana, G, Cenzano, S, Bouchard, L-S, Soboyejo, W, and Warren, WS. "Simultaneous acquisition of multiple orders of intermolecular multiple-quantum coherence images in vivo." Magnetic Resonance Imaging 22.10 SPEC. ISS. (2004): 1407-1412.
PMID
15707790
Source
scival
Published In
Magnetic Resonance Imaging
Volume
22
Issue
10 SPEC. ISS.
Publish Date
2004
Start Page
1407
End Page
1412
DOI
10.1016/j.mri.2004.10.019

Towards an anthrax detector using the femtosecond adaptive spectroscopic technique for coherent anti-Stokes Raman spectroscopy: Coherent anti-Stokes Raman spectroscopy signal from dipicolinic acid in bacterial spores

We present experimental evidence of a resonant coherent antiStokes Raman spectroscopy (CARS) signal from dipicolinic acid, a marker molecule in anthrax spores. We also show some evidence of resonant CARS signal associated with the 1000cm-1 resonance from Bacillus Globigii spores which are similar to anthrax spores. These results constitute a first step towards developing a rapid identification technique for bacterial spores.

Authors
Mehendale, M; Bosacchi, B; Gatzogiannis, E; Dogariu, A; Warren, WS; Scully, MO
MLA Citation
Mehendale, M, Bosacchi, B, Gatzogiannis, E, Dogariu, A, Warren, WS, and Scully, MO. "Towards an anthrax detector using the femtosecond adaptive spectroscopic technique for coherent anti-Stokes Raman spectroscopy: Coherent anti-Stokes Raman spectroscopy signal from dipicolinic acid in bacterial spores." Journal of Modern Optics 51.16-18 (2004): 2645-2653.
Source
scival
Published In
Journal of Modern Optics
Volume
51
Issue
16-18
Publish Date
2004
Start Page
2645
End Page
2653
DOI
10.1080/09500340412331286784

Rapid two-dimensional optical spectroscopy through acousto-optic pulse shaping

Phase-matching techniques are widely used to retrieve nonlinear optical signals of electronic and vibrational transitions. Here, collinear, phase cycled pulses are used to collect the same nonlinear signals in direct analogy to nuclear magnetic resonance studies. An acousto-optic pulse shaper is used to create suitable sequences of ultrashort pulses with arbitrary relative delays and phases. The rapid update rate of the acousto-optic modulator allows for impressive data rates.

Authors
Wagner, W; Tian, P; Chunqiang, LI; Semmlow, J; Warren, WS
MLA Citation
Wagner, W, Tian, P, Chunqiang, LI, Semmlow, J, and Warren, WS. "Rapid two-dimensional optical spectroscopy through acousto-optic pulse shaping." Journal of Modern Optics 51.16-18 (2004): 2655-2663.
Source
scival
Published In
Journal of Modern Optics
Volume
51
Issue
16-18
Publish Date
2004
Start Page
2655
End Page
2663
DOI
10.1080/09500340412331284858

Direct-detection DWDM and information transmission using infrared acousto-optic femtosecond pulse shaping

Acousto-optic modulator (AOM)-based pulse shaping permits precise spectrum slicing, which is useful for dense wavelength division multiplexed (DWDM)-based architectures. In essence, this method uses microsecond-duration radio frequency pulses to completely control the spectra of femtosecond laser pulses, hence achieves dramatic temporal data compression. We demonstrated the AOM pulse shaper as the modulator and a CCD camera with 256 pixels as the receiver. The spectrum of a 200 fs Erbium Doped Fiber Laser (EDFL) pulse was dispersed across the AOM's aperture (FWHM was 35 nm) and was then modulated in a conventional pulse shaper. We tested 87 channels with channel-spacing of 0.41 nm using a 518-MHz modulator, and 120 channels with channel-spacing of 0.29 nm using a 148-MHz modulator (in each case a 0.1 nm guard band was used). Starting from the original pulses, this modulation creates time slots of 43 ps and 63.4 ps respectively. The equivalent speed of the transmission will be 2.0 Tb/s and 1.9 Tb/s in a highly multiplexed system. The spectral efficiencies achieved in this experiment were ∼46%, approaching the theoretical limit of 50% for On-Off Keying (OOK) modulation. A benchmark image was successfully sent over the test bed.

Authors
Huang, F; Warren, WS
MLA Citation
Huang, F, and Warren, WS. "Direct-detection DWDM and information transmission using infrared acousto-optic femtosecond pulse shaping." Proceedings of SPIE - The International Society for Optical Engineering 5579.PART 2 (2004): 652-660.
Source
scival
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
5579
Issue
PART 2
Publish Date
2004
Start Page
652
End Page
660
DOI
10.1117/12.563513

Generation and detection of pulsed T-Rays for use in the study of biological and bio-terrorism issues

Terahertz (T-Rays) spectroscopy has recently emerged as a powerful method to access a heretofore barely explored region of the electromagnetic spectrum where fundamental molecular resonances occur. Besides their importance for fundamental research, these resonances could be used as signatures in the identification of molecular species and as sensitive probes in a wide variety of molecular processes. In this paper we consider the potential of THz spectroscopy in the application to relevant biomedical and homeland security problems such as the analysis of normal and diseased tissues and the detection of toxic biomolecules. As examples, we present preliminary experimental data which suggest that THz spectroscopy 1)can discriminate between cancerous and normal tissue, and 2) can reveal the presence of foreign substances hidden in an envelope and even allow their specific identification. This capability is of particular relevance as a straifghtforward homeland security tool for the detection of anthrax and other biotoxic molecules.

Authors
Jedju, T; Bosacchi, B; Warren, WS; Nahata, A; Kuenstner, T
MLA Citation
Jedju, T, Bosacchi, B, Warren, WS, Nahata, A, and Kuenstner, T. "Generation and detection of pulsed T-Rays for use in the study of biological and bio-terrorism issues." Proceedings of SPIE - The International Society for Optical Engineering 5411 (2004): 92-98.
Source
scival
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
5411
Publish Date
2004
Start Page
92
End Page
98
DOI
10.1117/12.541531

Evolutionary Pulse Shaping in CARS Signal Enhancement

We discuss the role of evolutionary adaptive algorithms in shaping femtosecond pulses with an eye toward their use in the quantum control of optical properties. In particular, we report preliminary results from an ongoing attempt to implement the recently proposed FAST CARS technique for the detection and identification of bacterial spores. In the initial phase of this project, we are studying the CARS signal from a deuterated water (D2O) solution of Dipicolinic Acid (DPA), which is an important constituent of the spores. We have detected CARS signal associated with the DPA vibrational resonances at ∼ 1,600 and ∼ 3,000cm-1. We also find preliminary evidence of a pulse shaping enhancement of the CARS intensity. This effect is weak, but significant. It is premature to ascribe it to any particular mechanism, but its detection encourages its optimization by searching the space of all possible pulse shapes via an evolutionary feedback algorithm.

Authors
Mehendale, M; Bosacchi, B; Warren, WS; Scully, MO
MLA Citation
Mehendale, M, Bosacchi, B, Warren, WS, and Scully, MO. "Evolutionary Pulse Shaping in CARS Signal Enhancement." Proceedings of SPIE - The International Society for Optical Engineering 5200 (2003): 46-55.
Source
scival
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
5200
Publish Date
2003
Start Page
46
End Page
55

Computational Intelligence in Bacterial Spore Detection & Identification

Optical techniques are very promising for detecting and identifying bacterial spores. They are potentially superior to the existing "wet chemistry" approaches regarding several important features of an effective alarm system, such as speed, in-field use, continuous monitoring, and reliability. In this paper we discuss the role that computational intelligence (CI) can play in the control and optimization of optical experiments, and in the analysis and interpretation of the large amount of data they provide. After a brief discussion of the use of CI in the classification of optical spectra, we introduce the recently proposed FAST CARS (Femtosecond Adaptive Spectroscopic Techniques for Coherent Anti-Stokes Raman Scattering) technique. Here the role of CI is essential: using an adaptive feedback approach based on genetic algorithms, the hardware system evolves and organizes itself to optimize the intensity of the CARS signal.

Authors
Bosacchi, B; Mehendale, M; Warren, WS; Rabitz, H; Scully, MO
MLA Citation
Bosacchi, B, Mehendale, M, Warren, WS, Rabitz, H, and Scully, MO. "Computational Intelligence in Bacterial Spore Detection & Identification." Proceedings of SPIE - The International Society for Optical Engineering 5200 (2003): 31-45.
Source
scival
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
5200
Publish Date
2003
Start Page
31
End Page
45

"Intermolecular Mulitple-Quantum Coherence of Imaging of Murine Tumors Depends on Choice of Dipolar Correlation Distance"

Authors
Bouchard, LS; Poptani, H; Rizi, RR; Glickson, JD; Warren, WS
MLA Citation
Bouchard, LS, Poptani, H, Rizi, RR, Glickson, JD, and Warren, WS. ""Intermolecular Mulitple-Quantum Coherence of Imaging of Murine Tumors Depends on Choice of Dipolar Correlation Distance"." Proc. Intl. Soc. Mag. Reson. Med. 11 (2003): 1112-. (Academic Article)
Source
manual
Published In
Proc. Intl. Soc. Mag. Reson. Med.
Issue
11
Publish Date
2003
Start Page
1112

"Magnetic Resonance Imaging of the Distant Dipolar Field in Structured Samples Using Intermolecular Multiple-Quantum Coherences of Various Orders"

Authors
Bouchard, LS; Tang, X; Chin, C; Wehrli, FW; Warren, WS
MLA Citation
Bouchard, LS, Tang, X, Chin, C, Wehrli, FW, and Warren, WS. ""Magnetic Resonance Imaging of the Distant Dipolar Field in Structured Samples Using Intermolecular Multiple-Quantum Coherences of Various Orders"." Proc. Intl. Soc. Mag. Reson. Med. 11 (2003): 1110-. (Academic Article)
Source
manual
Published In
Proc. Intl. Soc. Mag. Reson. Med.
Issue
11
Publish Date
2003
Start Page
1110

The prospects for high resolution optical brain imaging: The magnetic resonance perspective

Various analogs of NMR and MRI are now technically possible in optics; specifically, high-resolution laser-pulse shaping and complex pulse sequence generation with well-defined phase shifts has been demonstrated. Here we summarize this technology and discuss the potential for these methods to enhance optical functional imaging, competing with (and surpassing?) what is possible by functional MRI. © 2003 Elsevier Inc. All rights reserved.

Authors
Warren, WS; Wagner, W; Ye, T
MLA Citation
Warren, WS, Wagner, W, and Ye, T. "The prospects for high resolution optical brain imaging: The magnetic resonance perspective." Magnetic Resonance Imaging 21.10 (2003): 1225-1233.
PMID
14725930
Source
scival
Published In
Magnetic Resonance Imaging
Volume
21
Issue
10
Publish Date
2003
Start Page
1225
End Page
1233
DOI
10.1016/j.mri.2003.08.024

Simultaneous acquisition of multiple orders of intermolecular multiple-quantum coherence images

Recent studies have demonstrated the ability to detect images based on intermolecular multiple-quantum coherences (iMQCs) that correspond to flipping of two or more separated spins simultaneously, as opposed to conventional magnetic resonance where only one spin is flipped at a time. Until now, iMQC imaging has only acquired one coherence signal per pulse sequence. Here we report a new sequence that successfully detects five orders of coherence (2, 1, 0, -1, and -2-quantum coherence images) in one pulse sequence, with each signal having its full intensity. The simultaneous acquisition highlights substantial contrast differences between conventional and iMQC images, and between the different types of iMQC images. © 2003 Elsevier Inc. All rights reserved.

Authors
Tang, X; Ong, H; Shannon, K; Warren, WS
MLA Citation
Tang, X, Ong, H, Shannon, K, and Warren, WS. "Simultaneous acquisition of multiple orders of intermolecular multiple-quantum coherence images." Magnetic Resonance Imaging 21.10 (2003): 1141-1149.
PMID
14725921
Source
scival
Published In
Magnetic Resonance Imaging
Volume
21
Issue
10
Publish Date
2003
Start Page
1141
End Page
1149
DOI
10.1016/j.mri.2003.08.015

Isolating quantum coherences in structural imaging using intermolecular double-quantum coherence MRI

Intermolecular multiple-quantum coherence (iMQC) MR imaging provides a fundamentally different contrast mechanism. It allows probing tissue microstructure by tuning the direction and strength of the correlation gradient. However, iMQC images of a specific quantum-coherence can easily be contaminated by leakage signals from undesired quantum coherences (zero, single, and triple quantum coherence in this work). Using a modified double-quantum CRAZED imaging sequence, we show that signals originating from various coherence orders (M=0, 1, 2, 3) can be predicted in k-space and effectively isolated by means of a four-step phase cycling scheme and judicious choice of flip angles. Finally, preliminary data suggest the method to be able to provide information on trabecular bone architecture such as regional mean trabecular plate separation. © 2003 Elsevier Inc. All rights reserved.

Authors
Chin, C-L; Tang, X; Bouchard, L-S; Saha, PK; Warren, WS; Wehrli, FW
MLA Citation
Chin, C-L, Tang, X, Bouchard, L-S, Saha, PK, Warren, WS, and Wehrli, FW. "Isolating quantum coherences in structural imaging using intermolecular double-quantum coherence MRI." Journal of Magnetic Resonance 165.2 (2003): 309-314.
PMID
14643714
Source
scival
Published In
Journal of Magnetic Resonance
Volume
165
Issue
2
Publish Date
2003
Start Page
309
End Page
314
DOI
10.1016/j.jmr.2003.08.007

Relative-phase ambiguities in measurements of ultrashort pulses with well-separated multiple frequency components

A study is performed on relative-phase ambiguities in measurements of ultrashort pulses with well-separated multiple frequency components. It is shown that if a laser pulse consists of components that are well separated in the frequency domain, the self-referenced pulse characterization techniques are incapable of yielding the overall phase relation among the spectral components of the pulse. If a well-characterized reference pulse is available, spectral interferometry can determine the phase relation.

Authors
Keusters, D; Tan, H-S; O'Shea, P; Zeek, E; Trebino, R; Warren, WS
MLA Citation
Keusters, D, Tan, H-S, O'Shea, P, Zeek, E, Trebino, R, and Warren, WS. "Relative-phase ambiguities in measurements of ultrashort pulses with well-separated multiple frequency components." Journal of the Optical Society of America B: Optical Physics 20.10 (2003): 2226-2237.
Source
scival
Published In
Journal of the Optical Society of America B
Volume
20
Issue
10
Publish Date
2003
Start Page
2226
End Page
2237

Femtosecond phase-coherent two-dimensional spectroscopy

Femtosecond phase-coherent two-dimensional (2D) spectroscopy has been experimentally demonstrated as the direct optical analog of 2D nuclear magnetic resonance. An acousto-optic pulse shaper created a collinear three-pulse sequence with well-controlled and variable interpulse delays and phases, which interacted with a model atomic system of rubidium vapor. The desired nonlinear polarization was selected by phase cycling (coadding experimental results obtained with different interpulse phases). This method may enhance our ability to probe the femtosecond structural dynamics of macromolecules.

Authors
Tian, P; Keusters, D; Suzaki, Y; Warren, WS
MLA Citation
Tian, P, Keusters, D, Suzaki, Y, and Warren, WS. "Femtosecond phase-coherent two-dimensional spectroscopy." Science 300.5625 (2003): 1553-1555.
PMID
12791987
Source
scival
Published In
Science
Volume
300
Issue
5625
Publish Date
2003
Start Page
1553
End Page
1555
DOI
10.1126/science.1083433

Mid infrared pulse shaping by optical parametric amplification and its application to optical free induction decay measurement

We produce microjoule energy shaped mid infrared (MIR) pulses in an optical parametric amplification (OPA) process by imposing the phase and amplitude profile of an arbitrarily shaped pump pulse onto the idler pulse. Using phase locked pulses created using this technique, we measure for the first time, complex optical free induction decay (OFID) of the vibrational coherence of a C-H stretching mode. © 2003 Optical Society of America.

Authors
Tan, H-S; Warren, WS
MLA Citation
Tan, H-S, and Warren, WS. "Mid infrared pulse shaping by optical parametric amplification and its application to optical free induction decay measurement." Optics Express 11.9 (2003): 1021-1028.
Source
scival
Published In
Optics express
Volume
11
Issue
9
Publish Date
2003
Start Page
1021
End Page
1028

Effect of pulse propagation on the two-dimensional photon echo spectrum of multilevel systems

A perturbative method was used to investigate the effect of propagation on multilevel systems, specifically on the relative intensity and profile of the cross peaks. It was shown that both the peak profiles and the relative intensity of the peaks in a 2D spectrum change as the pulse propagates through the sample. The behavior of the peaks was found to be counterintuitive, and depends not only on the optical density, but also on the dynamics of the system.

Authors
Keusters, D; Warren, WS
MLA Citation
Keusters, D, and Warren, WS. "Effect of pulse propagation on the two-dimensional photon echo spectrum of multilevel systems." Journal of Chemical Physics 119.8 (2003): 4478-4489.
Source
scival
Published In
Journal of Chemical Physics
Volume
119
Issue
8
Publish Date
2003
Start Page
4478
End Page
4489
DOI
10.1063/1.1591175

Reduction of optical intensity noise by means of two-photon absorption

We demonstrate an all-optical intensity noise reduction technique by using two-photon absorption of ZnSe in a Z-scan configuration. We measure the nonlinear transmission and the shot-to-shot energy fluctuations of 860-nm intense femtosecond laser pulses. At a 40% nonlinear transmission level the noise in the pulse train is reduced to 24%. This yields an additional 40% reduction in the relative pulse energy fluctuation. A realistic theoretical treatment is presented and is found to be in good agreement with experimental results. © 2003 Optical Society of America.

Authors
Cao, H; Warren, WS; Dogariu, A; Wang, LJ
MLA Citation
Cao, H, Warren, WS, Dogariu, A, and Wang, LJ. "Reduction of optical intensity noise by means of two-photon absorption." Journal of the Optical Society of America B: Optical Physics 20.3 (2003): 560-563.
Source
scival
Published In
Journal of the Optical Society of America B
Volume
20
Issue
3
Publish Date
2003
Start Page
560
End Page
563

Towards a FAST-CARS anthrax detector: CARS signal from dipicolinic acid

An overview is given of experimental results towards the realization of an alternative optical technique, the FAST CARS (Femtosecond Adaptive Spectroscopic Technique for Coherent Anti-Stokes Raman Spectroscopy) approach. This proposal makes use of the CARS configuration, thus exploiting the specificity of the vibrational spectra, and attempts to maximize the signal intensity through a few enhancement mechanisms.

Authors
Mehendale, M; Bosacchi, B; Warren, WS; Scully, MO
MLA Citation
Mehendale, M, Bosacchi, B, Warren, WS, and Scully, MO. "Towards a FAST-CARS anthrax detector: CARS signal from dipicolinic acid." Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS 1 (2003): 311-312.
Source
scival
Published In
Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS
Volume
1
Publish Date
2003
Start Page
311
End Page
312

Infrared pulse shaping by parametric amplification

We create arbitrarily shaped ultrashort pulses in the mid infrared (∼3.0μm). The amplitude and phase profile of a shaped broadband near infrared signal pulse is transferred to the mid infrared idler pulse in a KNbO3 optical parametric amplification system pumped with a 805nm narrow bandwidth pump pulse.

Authors
Tan, H-S; Schreiber, E; Warren, WS
MLA Citation
Tan, H-S, Schreiber, E, and Warren, WS. "Infrared pulse shaping by parametric amplification." Springer Series in Chemical Physics 71 (2003): 202-204.
Source
scival
Published In
Springer Series in Chemical Physics
Volume
71
Publish Date
2003
Start Page
202
End Page
204

Ultrafast two-photon free induction decay

Phase sensitive measurement of two-photon induced coherence is demonstrated, using phase coherent pulse pairs. By using an acousto-optic pulse shaper the different coherence transfer pathways in the two-photon absorption process can be separated.

Authors
Keusters, D; Tian, P; Warren, WS
MLA Citation
Keusters, D, Tian, P, and Warren, WS. "Ultrafast two-photon free induction decay." Springer Series in Chemical Physics 71 (2003): 85-87.
Source
scival
Published In
Springer Series in Chemical Physics
Volume
71
Publish Date
2003
Start Page
85
End Page
87

Ultrafast measurement of two-photon absorption by loss modulation

We demonstrate a direct and sensitive technique for measuring two-photon absorption (TPA). An intensity-modulated femtosecond laser beam passes through a sample exhibiting TPA. A TPA signal at twice the modulation frequency is then generated and subsequently measured by a lock-in amplifier. The absolute TPA cross section of Rhodamine 6G at 800 nm is found to be (15.3 ± 2.0) × 10-50 cm4 s/photon and agrees well with previously published results obtained with much higher intensity [J. Chem. Phys. 112, 9201 (2000)]. Our method may be especially useful in measuring nonlinear absorptions of nonfluorescent materials. © 2002 Optical Society of America.

Authors
Tian, P; Warren, WS
MLA Citation
Tian, P, and Warren, WS. "Ultrafast measurement of two-photon absorption by loss modulation." Optics Letters 27.18 (2002): 1634-1636.
Source
scival
Published In
Optics Letters
Volume
27
Issue
18
Publish Date
2002
Start Page
1634
End Page
1636

Direct and sensitive measurement of two-photon absorption cross sections

Direct and sensitive measurement of two-photon absorption (TPA) cross sections was presented. As a proof of principle, δ was measured for rhodamine 6G (R6G) in methanol. Results showed that the technique using moderate power from a mode-locked laser gave sensitivity of 10-6 cm/GW.

Authors
Tian, P; Keusters, D; Warren, WS
MLA Citation
Tian, P, Keusters, D, and Warren, WS. "Direct and sensitive measurement of two-photon absorption cross sections." Pacific Rim Conference on Lasers and Electro-Optics, CLEO - Technical Digest (2002): 447-448.
Source
scival
Published In
Pacific Rim Conference on Lasers and Electro-Optics, CLEO - Technical Digest
Publish Date
2002
Start Page
447
End Page
448

Magnetization structure contrast based on intermolecular multiple-quantum coherences

In vivo and ex vivo MRI based on intermolecular multiple-quantum coherences (iMQC) is predicted to provide a fundamentally different source of contrast for MRI. This article investigates the dependence of image contrast upon the choice of correlation distance for a heterogeneous material. A closely packed array of parallel hollow cylinders was used to demonstrate signal intensity variations when the correlation distance becomes comparable to the gap size between the cylinders. The observed effects agree well with three-dimensional calculations of the time evolution of magnetization under the nonlinear Bloch equations. © 2002 Wiley-Liss, Inc.

Authors
Bouchard, L-S; Rizi, RR; Warren, WS
MLA Citation
Bouchard, L-S, Rizi, RR, and Warren, WS. "Magnetization structure contrast based on intermolecular multiple-quantum coherences." Magnetic Resonance in Medicine 48.6 (2002): 973-979.
PMID
12465106
Source
scival
Published In
Magnetic Resonance in Medicine
Volume
48
Issue
6
Publish Date
2002
Start Page
973
End Page
979
DOI
10.1002/mrm.10293

Signal interferences from turbulent spin dynamics in solution nuclear magnetic resonance spectroscopy

The signal interference from turbulent spin dynamics in solution nuclear magnetic resonance spectroscopy was discussed. The unexpected dynamics, triggered by the joint action of the radiation damping and the distant dipolar field deteriorates the performances of the certain pulse sequences incorporating weak pulsed field gradients and long evolution times. The effects were demonstrated in three general classes of gradient NMR applications including solvent signal suppression, diffusion measurements, and coherence pathway selection.

Authors
Huang, SY; Lin, Y-Y; Lisitza, N; Warren, WS
MLA Citation
Huang, SY, Lin, Y-Y, Lisitza, N, and Warren, WS. "Signal interferences from turbulent spin dynamics in solution nuclear magnetic resonance spectroscopy." Journal of Chemical Physics 116.23 (2002): 10325-10337.
Source
scival
Published In
Journal of Chemical Physics
Volume
116
Issue
23
Publish Date
2002
Start Page
10325
End Page
10337
DOI
10.1063/1.1467333

High-resolution indirect pulse shaping by parametric transfer

The phase and amplitude profile of a shaped pulse in the visible is transferred to a pulse in the near-infrared via an optical parametric amplification (OPA) process. Complex shaped pulses, such as multiple-pulse trains and pulses with high-order phase chirp, are produced at 1.2 μm. Theoretical conditions necessary for high-fidelity parametric shape transfer are discussed. Similar schemes can be implemented for other OPA systems pumped at near-infrared wavelengths to generate high-resolution shaped pulses in the mid-infrared. © 2002 Optical Society of America.

Authors
Tan, H-S; Schreiber, E; Warren, WS
MLA Citation
Tan, H-S, Schreiber, E, and Warren, WS. "High-resolution indirect pulse shaping by parametric transfer." Optics Letters 27.6 (2002): 439-441.
Source
scival
Published In
Optics Letters
Volume
27
Issue
6
Publish Date
2002
Start Page
439
End Page
441

Understanding third-order dipolar effects in solution nuclear magnetic resonance: Hahn echo decays and intermolecular triple-quantum coherences

The coupled-spin framework is used to take into account the properties of the "third-order experiments," namely Hahn echo decay and triple-quantum CRAZED. It is shown that the Hahn echo decay reflects the unique contrast present in other CRAZED experiments, but that double-quantum and zero-quantum experiments are more useful.

Authors
Warren, WS; Huang, SY; Ahn, S; Lin, YY
MLA Citation
Warren, WS, Huang, SY, Ahn, S, and Lin, YY. "Understanding third-order dipolar effects in solution nuclear magnetic resonance: Hahn echo decays and intermolecular triple-quantum coherences." Journal of Chemical Physics 116.5 (2002): 2075-2084.
Source
scival
Published In
Journal of Chemical Physics
Volume
116
Issue
5
Publish Date
2002
Start Page
2075
End Page
2084
DOI
10.1063/1.1419061

Spin chaos in magnetic resonance

The joint action of two readily observed effects in solution magnetic resonance- radiation damping and the dipolar field-are shown to generate spatiotemporal chaos in routine experiments. The extreme sensitivity of the chaotic spin dynamics to experimental conditions during the initial evolution period can be used to construct a spin amplifier to enhance sensitivity and contrast in magnetic resonance spectroscopy and imaging. Alternatively, amplification of intrinsic spin noise or tiny experimental perturbations such as temperature gradient fluctuations leads to signal interferences and highly irreproducible measurements. Controlling the underlying chaotic evolution provides the crucial link between amplifying weak signals and counteracting unwanted signal fluctuations.

Authors
Lin, Y-Y; Huang, SY; Lisitza, N; Warren, WS
MLA Citation
Lin, Y-Y, Huang, SY, Lisitza, N, and Warren, WS. "Spin chaos in magnetic resonance." Proceedings of SPIE - The International Society for Optical Engineering 4787 (2002): 124-131.
Source
scival
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
4787
Publish Date
2002
Start Page
124
End Page
131
DOI
10.1117/12.455874

Frequency-domain differential phase-shift keying (FD-DPSK) of ultrafast laser pulses

The frequency-domain differential phase-shift-keying (DPSK) using ultrafast laser pulses has been demonstrated. Spectral coding based on acoustic optical modulator pulse shaping is used for modulation, and the ultrafast pulse characterization based on spectral interferometry is used for demodulation. The encoded differential phase pattern is successfully retrieved after transmission over 4-km dispersion-shifted fiber, which induces substantial nonlinear distortions.

Authors
Yang, W; Kobayashi, H; Warren, WS
MLA Citation
Yang, W, Kobayashi, H, and Warren, WS. "Frequency-domain differential phase-shift keying (FD-DPSK) of ultrafast laser pulses." IEEE Photonics Technology Letters 14.2 (2002): 215-217.
Source
scival
Published In
IEEE Photonics Technology Letters
Volume
14
Issue
2
Publish Date
2002
Start Page
215
End Page
217
DOI
10.1109/68.980526

Multidimensional symmetry in a three-dimensional world

Authors
Warren, WS
MLA Citation
Warren, WS. "Multidimensional symmetry in a three-dimensional world." Science 294.5546 (2001): 1475-1476.
Source
scival
Published In
Science
Volume
294
Issue
5546
Publish Date
2001
Start Page
1475
End Page
1476
DOI
10.1126/science.1066542

Fast-frequency-hopping modulation and detection demonstration

We demonstrate fast-frequency-hopping modulation that exploits the unique features of acousto-optic-modulator based laser pulse shaping and the spectrally and temporally resolved upconversion technique (STRUT) pulse-characterization method. These pulses have been specifically designed so that they can be characterized by the STRUT, without any processing of the STRUT data set. We present examples of complex fast-frequency-hopping laser pulses that have been generated and characterized by our pulse-shaping system and STRUT. We discuss the theoretical limitations on the data rate that can be obtained with such a technique. © 2001 Optical Society of America.

Authors
Fetterman, MR; Davis, JC; Tan, H-S; Yang, W; Goswami, D; Rhee, J-K; Warren, WS
MLA Citation
Fetterman, MR, Davis, JC, Tan, H-S, Yang, W, Goswami, D, Rhee, J-K, and Warren, WS. "Fast-frequency-hopping modulation and detection demonstration." Journal of the Optical Society of America B: Optical Physics 18.9 (2001): 1372-1376.
Source
scival
Published In
Journal of the Optical Society of America B
Volume
18
Issue
9
Publish Date
2001
Start Page
1372
End Page
1376

Generation and amplification of ultrashort shaped pulses in the visible by a two-stage noncollinear optical parametric process

We report the generation and amplification of ultrashort shaped pulses in the visible by a two-stage non-collinear optical parametric amplification process. Phase and amplitude profiles of the shaped pulses are conserved in our amplification scheme. The energy losses normally associated with the production of complex shaped pulses are eliminated. © 2001 Optical Society of America.

Authors
Tan, H-S; Warren, WS; Schreiber, E
MLA Citation
Tan, H-S, Warren, WS, and Schreiber, E. "Generation and amplification of ultrashort shaped pulses in the visible by a two-stage noncollinear optical parametric process." Optics Letters 26.22 (2001): 1812-1814.
Source
scival
Published In
Optics Letters
Volume
26
Issue
22
Publish Date
2001
Start Page
1812
End Page
1814

Femtosecond polarization detection using high-speed pulse shaping

We demonstrate a method for femtosecond, phase sensitive detection of optical polarization, using an acousto-optic pulse shaper to create a sequence of up to several hundred phase coherent pulses. Essential to this method is the ability of the acousto-optic pulse shaper to update the phase relation of the pulses in the sequence on a nanosecond timescale. The method is demonstrated by measuring the optical free induction decay of rubidium vapor, and can be particularly useful for experiments involving very low or very high optical densities. It can easily be extended to multidimensional spectroscopy.

Authors
Keusters, D; Tian, P; Warren, WS
MLA Citation
Keusters, D, Tian, P, and Warren, WS. "Femtosecond polarization detection using high-speed pulse shaping." Springer Series in Chemical Physics 66 (2001): 165-167.
Source
scival
Published In
Springer Series in Chemical Physics
Volume
66
Publish Date
2001
Start Page
165
End Page
167

Generation, amplification and characterization of tunable visible ultrashort shaped pulses

By producing non-collinear optical amplification (NOPA) with an internal acousto-optic modulator (AOM), we generate amplified shaped ultrashort pulses (∼5μJ, <50fs) tunable from 500 to 700nm with up to 50THz bandwidths. The shaped pulses are fully characterized by a variation of the spectrally and temporally resolved up-conversion technique (STRUT).

Authors
Tan, H-S; Warren, WS; Schreiber, E
MLA Citation
Tan, H-S, Warren, WS, and Schreiber, E. "Generation, amplification and characterization of tunable visible ultrashort shaped pulses." Springer Series in Chemical Physics 66 (2001): 105-107.
Source
scival
Published In
Springer Series in Chemical Physics
Volume
66
Publish Date
2001
Start Page
105
End Page
107

Quadrature spectral interferometric detection and pulse shaping

We introduce a new variant of spectral interferometry, using spectrally dispersed ultrafast laser pulses and quadrature detection to measure optical thickness variations related to surface structure. We can resolve surface features with depths of 3 mm to 25 nm, using a lateral resolution of ∼100 μm. Quadrature detection gives a larger dynamic range and solves the sign ambiguity problem. This method has potential applications in device manufacture, optical communications, and error compensation in pulse shaping. © 2001 Optical Society of America.

Authors
Huang, F; Yang, W; Warren, WS
MLA Citation
Huang, F, Yang, W, and Warren, WS. "Quadrature spectral interferometric detection and pulse shaping." Optics Letters 26.6 (2001): 382-384.
Source
scival
Published In
Optics Letters
Volume
26
Issue
6
Publish Date
2001
Start Page
382
End Page
384

Experimental characterization of intermolecular multiple-quantum coherence pumping efficiency in solution NMR

The behavior of intermolecular multiple-quantum coherences in a variety of simple liquids with different chemical and magnetic properties is investigated experimentally and modeled by numerical simulations based on modified Bloch equations. The effects of spin concentration, temperature, intramolecular conformational flexibility, chemical exchange, and spin-spin coupling on the formation of high-order coherences are examined. It is shown that any process that makes the Larmor frequency time-dependent may interfere with the formation of these coherences. Good agreement is achieved between experiments and simulation, using independently known values of the magnetization density, the rate constants for translational diffusion, spin-spin and spin-lattice relaxation, and radiation damping. © 2001 Academic Press.

Authors
Zhang, H; Lizitsa, N; Bryant, RG; Warren, WS
MLA Citation
Zhang, H, Lizitsa, N, Bryant, RG, and Warren, WS. "Experimental characterization of intermolecular multiple-quantum coherence pumping efficiency in solution NMR." Journal of Magnetic Resonance 148.1 (2001): 200-208.
PMID
11133293
Source
scival
Published In
Journal of Magnetic Resonance
Volume
148
Issue
1
Publish Date
2001
Start Page
200
End Page
208
DOI
10.1006/jmre.2000.2195

High-ratio electro-optical data compression for massive accessing networks using AOM-based ultrafast pulse shaping

Electro-optical data compression was demonstrated using the acousto-optic modulator (AOM) based ultrafast pulse shaping techniques. The comparison of electronic data packet into an optical data packet with effective data rate was demonstrated. The AOM-based pulse shaping compressed a 14-bit data frame of slower electronic signal into one single 20 picosecond time slot of the optical channel. The high ratio data compression technique enabled electronic end-user to share the optical channel directly.

Authors
Yang, W; Fetterman, MR; Goswami, D; Warren, WS
MLA Citation
Yang, W, Fetterman, MR, Goswami, D, and Warren, WS. "High-ratio electro-optical data compression for massive accessing networks using AOM-based ultrafast pulse shaping." Journal of Optical Communications 22.1 (2001): 15-18.
Source
scival
Published In
Journal of Optical Communications
Volume
22
Issue
1
Publish Date
2001
Start Page
15
End Page
18

Amplified shaped ultrashort pulses in the visible by a double stage non-collinear optical parametric process

A double stage noncollinear optical parametric process was used to generate amplified shaped ultrashort pulses in the visible light range. The pulses were shaped in the spectral domain by the Acousto-optic modulation (AOM) technique. Pulse shapes were characterized by a cross-correlation variant of the spectrally and temporally resolved upconversion technique (STRUT). Amplification of the shaped pulse by the non-collinear optical process recovered a significant amount of energy lost in the pulse shaping process.

Authors
Tan, H-S; Warren, WS; Schreiber, E
MLA Citation
Tan, H-S, Warren, WS, and Schreiber, E. "Amplified shaped ultrashort pulses in the visible by a double stage non-collinear optical parametric process." Conference on Lasers and Electro-Optics Europe - Technical Digest (2001): 49--.
Source
scival
Published In
Conference on Lasers and Electro-Optics Europe - Technical Digest
Publish Date
2001
Start Page
49-

Ultrafast laser pulse spectral domain differential phase shift keying

Pulse spectral-domain differential-phase-shift-keying has been demonstrated using AOM-based pulse shaping for modulation and spectral interferometry for demodulation. The encoded differential phase is successfully retrieved despite of the nonlinear distortions after 4-km dispersion-shifted fiber transmission.

Authors
Yang, W; Kobayashi, H; Warren, WS
MLA Citation
Yang, W, Kobayashi, H, and Warren, WS. "Ultrafast laser pulse spectral domain differential phase shift keying." Conference on Optical Fiber Communication, Technical Digest Series 54.3 (2001): WDD45/1-WDD45/3.
Source
scival
Published In
Conference on Optical Fiber Communication, Technical Digest Series
Volume
54
Issue
3
Publish Date
2001
Start Page
WDD45/1
End Page
WDD45/3

Phase lock loop control of two optical pulses and pulse shaping at 1.55 μm

Feedback phase control of two optical pulses and its application for the optimization of acousto-optic pulse shaping was investigated. The difference between the reference pulse and target, provided feedback to the RF control signal and permitted closed loop optimization. The comparison of spectral interference pattern to one obtained after a π/2 phase shift in AOM driving voltage resolved the sign ambiguity with phase leading or lagging the reference point and doubled the dynamic range.

Authors
Huang, F; Warren, WS
MLA Citation
Huang, F, and Warren, WS. "Phase lock loop control of two optical pulses and pulse shaping at 1.55 μm." Conference on Lasers and Electro-Optics Europe - Technical Digest (2001): 268-269.
Source
scival
Published In
Conference on Lasers and Electro-Optics Europe - Technical Digest
Publish Date
2001
Start Page
268
End Page
269

An all-optical noise eater

The shot-to-shot energy fluctations of a laser was reduced using nonlinear absorption. Two-photon absorption (2PA) was used as the optical limiting mechanism. The histograms of input and output pulses were examined and standard deviatation for each set was calculated. Reduction in noise figure was demonstrated by allowing reduced throughput of the device.

Authors
Cao, H; Dogariu, A; Kuzmich, A; Warren, WS; Wang, LJ
MLA Citation
Cao, H, Dogariu, A, Kuzmich, A, Warren, WS, and Wang, LJ. "An all-optical noise eater." Conference on Lasers and Electro-Optics Europe - Technical Digest (2001): 509-510.
Source
scival
Published In
Conference on Lasers and Electro-Optics Europe - Technical Digest
Publish Date
2001
Start Page
509
End Page
510

Intermolecular zero-quantum coherence imaging of the human brain.

The first intermolecular zero-quantum coherence (iZQC) MR images of the human brain at 4T are presented. To generate iZQC images, a modified echo-planar imaging pulse sequence was used which included an additional 45 degrees RF pulse and a correlation gradient. The observability and nonconventional contrast of human brain iZQC images at 4T is demonstrated. Axial images are presented for various pulse sequence parameters, and a zero-quantum relaxation map is obtained.

Authors
Rizi, RR; Ahn, S; Alsop, DC; Garrett-Roe, S; Mescher, M; Richter, W; Schnall, MD; Leigh, JS; Warren, WS
MLA Citation
Rizi, RR, Ahn, S, Alsop, DC, Garrett-Roe, S, Mescher, M, Richter, W, Schnall, MD, Leigh, JS, and Warren, WS. "Intermolecular zero-quantum coherence imaging of the human brain." Magnetic resonance in medicine 43.5 (May 2000): 627-632.
PMID
10800025
Source
epmc
Published In
Magnetic Resonance in Medicine
Volume
43
Issue
5
Publish Date
2000
Start Page
627
End Page
632
DOI
10.1002/(sici)1522-2594(200005)43:5<627::aid-mrm2>3.0.co;2-j

High-resolution, >1 GHz NMR in unstable magnetic fields

Resistive or resistive-superconducting hybrid magnets generate spatial homogeneity and temporal stability. As a result, these magnets are unacceptable for high-resolution experiments. The possibility of effectively homogenizing and stabilizing these magnets by spin manipulations that exploit intermolecular zero-quantum coherences (iZQCs) is demonstrated.

Authors
Lin, Y-Y; Ahn, S; Murali, N; Brey, W; Bowers, CR; Warren, WS
MLA Citation
Lin, Y-Y, Ahn, S, Murali, N, Brey, W, Bowers, CR, and Warren, WS. "High-resolution, >1 GHz NMR in unstable magnetic fields." Physical Review Letters 85.17 (2000): 3732-3735.
PMID
11030993
Source
scival
Published In
Physical Review Letters
Volume
85
Issue
17
Publish Date
2000
Start Page
3732
End Page
3735
DOI
10.1103/PhysRevLett.85.3732

Resurrection of crushed magnetization and chaotic dynamics in solution NMR spectroscopy

We show experimentally and theoretically that two readily observed effects in solution nuclear magnetic resonance (NMR) - radiation damping and the dipolar field - combine to generate bizarre spin dynamics (including chaotic evolution) even with extraordinarily simple sequences. For example, seemingly insignificant residual magnetization after a crusher gradient triggers exponential regrowth of the magnetization, followed by aperiodic turbulent spin motion. The estimated Lyapunov exponent suggests the onset of spatial-temporal chaos and the existence of chaotic attractors. This effect leads to highly irreproducible experimental decays that amplify minor nonuniformities such as temperature gradients. Imaging applications and consequences for other NMR studies are discussed.

Authors
Lin, Y-Y; Lisitza, N; Ahn, S; Warren, WS
MLA Citation
Lin, Y-Y, Lisitza, N, Ahn, S, and Warren, WS. "Resurrection of crushed magnetization and chaotic dynamics in solution NMR spectroscopy." Science 290.5489 (2000): 118-121.
Source
scival
Published In
Science
Volume
290
Issue
5489
Publish Date
2000
Start Page
118
End Page
121
DOI
10.1126/science.290.5489.118

Numerical Studies of Intermolecular Multiple Quantum Coherences: High-Resolution NMR in Inhomogeneous Fields and Contrast Enhancement in MRI

A fast, efficient numerical algorithm is used to study intermolecular zero-quantum coherences (iZQCs) and double-quantum coherences (iDQCs) in two applications where the three-dimensional structure of the magnetization is important: high-resolution NMR in inhomogeneous fields and contrast enhancement in MRI. Simulations with up to 2 million coupled volume elements (256 × 256 × 32) show that iZQCs can significantly narrow linewidths in the indirectly detected dimension of systems with inhomogeneous fields and explore the effects of shape and orientation of the inhomogeneities. In addition, this study shows that MR images from iZQC and iDQC CRAZED pulse sequences contain fundamentally new contrast, and a modified CRAZED pulse sequence (modCRAZED) can isolate the contrast from chemically inequivalent Spins. © 2000 Academic Press.

Authors
Garrett-Roe, S; Warren, WS
MLA Citation
Garrett-Roe, S, and Warren, WS. "Numerical Studies of Intermolecular Multiple Quantum Coherences: High-Resolution NMR in Inhomogeneous Fields and Contrast Enhancement in MRI." Journal of Magnetic Resonance 146.1 (2000): 1-13.
PMID
10968952
Source
scival
Published In
Journal of Magnetic Resonance
Volume
146
Issue
1
Publish Date
2000
Start Page
1
End Page
13
DOI
10.1006/jmre.2000.2096

Automatic quantum error correction

The ability to engineer the interaction between a bath and a system is demonstrated. It is shown that this ability makes it possible to implement quantum error correction simply through dissipative dynamics, without requiring any external manipulation. An example that uses only well-understood magnetic interactions is considered to demonstrate the potential for a physically realizable implementation of automatic quantum error correcting codes.

Authors
Barnes, JP; Warren, WS
MLA Citation
Barnes, JP, and Warren, WS. "Automatic quantum error correction." Physical Review Letters 85.4 (2000): 856-859.
Source
scival
Published In
Physical Review Letters
Volume
85
Issue
4
Publish Date
2000
Start Page
856
End Page
859
DOI
10.1103/PhysRevLett.85.856

Functional magnetic resonance imaging with intermolecular multiple- quantum coherences

For the first time, we demonstrate here functional magnetic resonance imaging (fMRI) using intermolecular multiple-quantum coherences (iMQCs). iMQCs are normally not observed in liquid-state NMR because dipolar interactions between spins average to zero. If the magnetic isotropy of the sample is broken through the use of magnetic field gradients, dipolar couplings can reappear, and hence iMQCs can be observed. Conventional (BOLD) fMRI measures susceptibility variations averaged over each voxel. In the experiment performed here, the sensitivity of iMQCs to frequency variations over mesoscopic and well-defined distances is exploited. We show that iMQC contrast is qualitatively and quantitatively different from BOLD contrast in a visual stimulation task. While the number of activated pixels is smaller in iMQC contrast, the intensity change in some pixels exceeds that of BOLD contrast severalfold. (C) 2000 Elsevier Science Inc.

Authors
Richter, W; Richter, M; Warren, WS; Merkle, H; Andersen, P; Adriany, G; Ugurbil, K
MLA Citation
Richter, W, Richter, M, Warren, WS, Merkle, H, Andersen, P, Adriany, G, and Ugurbil, K. "Functional magnetic resonance imaging with intermolecular multiple- quantum coherences." Magnetic Resonance Imaging 18.5 (2000): 489-494.
PMID
10913709
Source
scival
Published In
Magnetic Resonance Imaging
Volume
18
Issue
5
Publish Date
2000
Start Page
489
End Page
494
DOI
10.1016/S0730-725X(00)00133-8

Driving wave packet recurrences with optimally modulated laser pulses

In the weak-field limit, laser pulses optimized to induce vibrational wave packet recurrences in excited state potentials were calculated for Morse oscillators and for a real system [the X1Σ+ and A 3II(1) states of IBr]. The performance of the optimized pulses was studied via simulated wave packet propagation. Such optimal light fields may be computationally generated given only the form of the electronic potential surfaces, knowledge of the particular ground state supplying population, and simple molecular constants. Thus it should be possible to use the modulation of light fields experimentally optimized to achieve recurrences in order to obtain substantial information regarding previously uncharacterized potential surfaces in both diatomic and polyatomic molecules. Moreover, it should be possible to generalize this approach to the strong-field limit. © 2000 American Institute of Physics.

Authors
Goodson, BM; Goswami, D; Rabitz, H; Warren, WS
MLA Citation
Goodson, BM, Goswami, D, Rabitz, H, and Warren, WS. "Driving wave packet recurrences with optimally modulated laser pulses." Journal of Chemical Physics 112.11 (2000): 5081-5090.
Source
scival
Published In
Journal of Chemical Physics
Volume
112
Issue
11
Publish Date
2000
Start Page
5081
End Page
5090

Generation and amplification of shaped ultrafast laser pulses, tunable between 500 to 700 nm

If quantum control and spectroscopy is to be applied in general to a wide range of atomic or molecular systems, methods should be developed to generate shaped optical pulses at widely tunable wavelengths to fit the corresponding resonance frequency of the various systems under study. This article describes and demonstrates such a method.

Authors
Tan, H-S; Schreiber, E; Warren, WS
MLA Citation
Tan, H-S, Schreiber, E, and Warren, WS. "Generation and amplification of shaped ultrafast laser pulses, tunable between 500 to 700 nm." Pacific Rim Conference on Lasers and Electro-Optics, CLEO - Technical Digest (2000): 475--.
Source
scival
Published In
Pacific Rim Conference on Lasers and Electro-Optics, CLEO - Technical Digest
Publish Date
2000
Start Page
475-

Intermolecular multiple quantum coherences in liquids

In the early 1990s, the traditional framework of NMR spectroscopy was challenged through a series of simple experiments. The pulse sequences used consisted of a few RF pulses and a few gradient pulses, and the samples were mixtures of simple molecules. The spectra showed unexpected cross peaks between spins in different molecules. In order to explain these results, two basic assumptions had to be revisited: (1) the high-temperature approximation to the Boltzmann distribution at equilibrium, and (2) the cancellation of dipolar couplings in solution. A close look at the physics involved showed that correlations between spins in separate molecules exist even after a single pulse, and that dipolar couplings can make these correlations visible in the presence of gradient pulses. A comprehensive description of the effect is given here, and some present and future applications are discussed. © 2000 lohn Wiley & Sons, Inc.

Authors
Richter, W; Warren, WS
MLA Citation
Richter, W, and Warren, WS. "Intermolecular multiple quantum coherences in liquids." Concepts in Magnetic Resonance 12.6 (2000): 396-409.
Source
scival
Published In
Concepts in Magnetic Resonance
Volume
12
Issue
6
Publish Date
2000
Start Page
396
End Page
409

Functional MRI with intermolecular multiple quantum coherences

Authors
Richter, W; Richter, M; Warren, W; Merkle, H; Adriany, G; Andersen, P; Ugtirbil, K
MLA Citation
Richter, W, Richter, M, Warren, W, Merkle, H, Adriany, G, Andersen, P, and Ugtirbil, K. "Functional MRI with intermolecular multiple quantum coherences." NeuroImage 11.5 PART II (2000): S451-.
Source
scival
Published In
NeuroImage
Volume
11
Issue
5 PART II
Publish Date
2000
Start Page
S451

Intermolecular zero-quantum coherence imaging of the human brain

The first intermolecular zero-quantum coherence (iZQC) MR images of the human brain at 4T are presented. To generate iZQC images, a modified echo- planar imaging pulse sequence was used which included an additional 45°RF pulse and a correlation gradient. The observability and nonconventional contrast of human brain iZQC images at 4T is demonstrated. Axial images are presented for various pulse sequence parameters, and a zero-quantum relaxation map is obtained. (C) 2000 Wiley-Liss, Inc.

Authors
Rizi, RR; Ahn, S; Alsop, DC; Garrett-Roe, S; Mescher, M; Richter, W; Schnall, MD; Leigh, JS; Warren, WS
MLA Citation
Rizi, RR, Ahn, S, Alsop, DC, Garrett-Roe, S, Mescher, M, Richter, W, Schnall, MD, Leigh, JS, and Warren, WS. "Intermolecular zero-quantum coherence imaging of the human brain." Magnetic Resonance in Medicine 43.5 (2000): 627-632.
Source
scival
Published In
Magnetic Resonance in Medicine
Volume
43
Issue
5
Publish Date
2000
Start Page
627
End Page
632
DOI
10.1002/(SICI)1522-2594(200005)43:5<627::AID-MRM2>3.0.CO;2-J

Spectral interference measurement of nonlinear pulse propagation dynamics in optical fibers

Ultrafast pulse shaping and ultrafast pulse spectral phase-retrieval techniques are used in the spectral interference measurement of nonlinear pulse propagation dynamics in dispersion-shifted optical fiber. Nonlinear responses in both amplitude profile and phase profile of the pulses at zero-dispersion wavelength as well as at nonzero-dispersion wavelength are directly measured. A numerical simulation that uses a third-oder-dispersion-included nonlinear Schrödinger equation gives excellent agreement with the experimental data. © 2000 Optical Society of America.

Authors
Yang, W; Fetterman, MR; Davis, JC; Warren, WS
MLA Citation
Yang, W, Fetterman, MR, Davis, JC, and Warren, WS. "Spectral interference measurement of nonlinear pulse propagation dynamics in optical fibers." Optics Letters 25.1 (2000): 22-24.
Source
scival
Published In
Optics Letters
Volume
25
Issue
1
Publish Date
2000
Start Page
22
End Page
24

Real-time adaptive amplitude feedback in an AOM-based ultrafast optical pulse shaping system

We demonstrate real-time adaptive amplitude feedback in an AOM-based ultrafast optical pulse shaping system operating at λ = 1550 nm wavelength for optical communication applications. At the optimized feedback depth, a simple negative feedback algorithm converges in fewer than 10 iterations to within 5% of the target shape. This technique may be very useful for many applications including spectrum-sliced WDM.

Authors
Yang, W; Huang, F; Fetterman, MR; Davis, JC; Goswami, D; Warren, WS
MLA Citation
Yang, W, Huang, F, Fetterman, MR, Davis, JC, Goswami, D, and Warren, WS. "Real-time adaptive amplitude feedback in an AOM-based ultrafast optical pulse shaping system." IEEE Photonics Technology Letters 11.12 (1999): 1665-1667.
Source
scival
Published In
IEEE Photonics Technology Letters
Volume
11
Issue
12
Publish Date
1999
Start Page
1665
End Page
1667
DOI
10.1109/68.806881

Role of pulse phase and direction in two-dimensional optical spectroscopy

This paper examines the parallels between magnetic resonance and optical spectroscopy, with the goal of determining to what extent the benefits of 2DNMR might be extended into the optical regime. Precise optical analogues of the simplest 2DNMR sequences (collinear pulse sequences with phased laser pulse generation, phase sensitive detection, and phase cycling) are now feasible, and we demonstrate that they do generate cross-peaks which reveal common energy levels, even when averaged over the distribution of pulse flip angles expected in most optical experiments. One enormous difference between laser and NMR experiments-the use of pulses in different directions in optics-can be exploited to eliminate much of the phase cycling required in NMR. Phase control does permit rotating-frame detection, which is likely to be a substantial practical advantage. Finally, we point out optical analogues of the simplest 2DNMR sequences (COSY and NOESY) will likely add little to our understanding of ultrafast dynamics. Optical analogues of more complex 2D sequences, combining phase control for selective refocusing with noncollinear pulse generation for coherence pathway selection, show more promise. © 1999 American Chemical Society.

Authors
Keusters, D; Tan, H-S; Warren, WS
MLA Citation
Keusters, D, Tan, H-S, and Warren, WS. "Role of pulse phase and direction in two-dimensional optical spectroscopy." Journal of Physical Chemistry A 103.49 (1999): 10369-10380.
Source
scival
Published In
The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
Volume
103
Issue
49
Publish Date
1999
Start Page
10369
End Page
10380

Multiple spin echo generation by gradients of the radio frequency amplitude: Two-dimensional nutation spectroscopy and multiple rotary echoes

NMR (nuclear magnetic resonance) nutation is treated with respect to demagnetizing-field effects on the evolution of spin coherences. A two-dimensional NMR nutation spectroscopy scheme is suggested consisting of a single radio frequency (RF) pulse and a free-evolution period. The RF pulse amplitude as well as the external magnetic field are assumed to be subject to gradients in the same but otherwise arbitrary direction. Cross peaks are predicted as frequency domain counterparts of multiple echoes. It is suggested to analyze the cross peak shape in terms of distributions of internal gradients arising from magnetic susceptibility inhomogeneities in heterogeneous samples. Furthermore, a pulse scheme solely based on gradients of the RF amplitude is treated resulting in the prediction of multiple rotary echoes as counterparts to the conventional rotary echo. The origin again is evolution in the presence of spatially modulated longitudinal magnetization in the tilted rotating frame. © 1999 American Institute of Physics.

Authors
Kimmich, R; Ardelean, I; Lin, Y-Y; Ahn, S; Warren, WS
MLA Citation
Kimmich, R, Ardelean, I, Lin, Y-Y, Ahn, S, and Warren, WS. "Multiple spin echo generation by gradients of the radio frequency amplitude: Two-dimensional nutation spectroscopy and multiple rotary echoes." Journal of Chemical Physics 111.14 (1999): 6501-6509.
Source
scival
Published In
Journal of Chemical Physics
Volume
111
Issue
14
Publish Date
1999
Start Page
6501
End Page
6509

Decoherence and programmable quantum computation

When coherent states of the electromagnetic field are used to drive the evolution of a quantum computer, a decoherence results due to the back reaction from the qubits onto the fields. We show how to calculate this effect. No assumptions about the environment are necessary, so this represents a useful model to test the fidelity of quantum error correcting codes. We examine two cases of interest. First, the decoherence from the Walsh-Hadamard transformations in Grover's search algorithm is found [Phys. Rev. Lett. 79, 325 (1997)]. Interference effects, and decoherence-dependent phases, are present that could be useful in reducing the decoherence. Second, Shor's fault-tolerant controlled-NOT gate is examined, utilizing frequency-selective pulses [Proceedings, 35th Annual Symposium on Foundations of Computer Science (IEEE Press, New York, 1994), pp. 56-65]. This implementation is found not to be optimal in regards to fault-tolerant quantum computation.

Authors
Barnes, JP; Warren, WS
MLA Citation
Barnes, JP, and Warren, WS. "Decoherence and programmable quantum computation." Physical Review A - Atomic, Molecular, and Optical Physics 60.6 (1999): 4363-4374.
Source
scival
Published In
Physical Review A - Atomic, Molecular, and Optical Physics
Volume
60
Issue
6
Publish Date
1999
Start Page
4363
End Page
4374

Visualizing the dipolar field in solution NMR and MR imaging: Three-dimensional structure simulations

We propose and demonstrate an efficient numerical approach which switches back and forth between real and Fourier spaces to handle dipolar field effects for heterogeneous three-dimensional structures. Applications to magnetic resonance imaging and improving field homogeneity are discussed.

Authors
Enss, T; Ahn, S; Warren, WS
MLA Citation
Enss, T, Ahn, S, and Warren, WS. "Visualizing the dipolar field in solution NMR and MR imaging: Three-dimensional structure simulations." Chemical Physics Letters 305.1-2 (1999): 101-108.
Source
scival
Published In
Chemical Physics Letters
Volume
305
Issue
1-2
Publish Date
1999
Start Page
101
End Page
108

Selective excitation of high vibrational states using Raman chirped adiabatic passage

Calculations indicate that high vibrational states of oxygen and chlorine can be excited using a series of nonresonant Raman pulses, where both the pump and the Stokes pulses are chirped with linear frequency sweeps. Most of the previously reported coherent processes (such as simple adiabatic passage) are seriously degraded when rotational effects are included. However, we find that the laser pulse parameters (intensity and bandwidth) required to invert population into high vibrational states via Raman chirped adiabatic passage are achievable using technology that is currently available. Applications to homonuclear diatomic molecules are discussed in detail. © 1999 American Institute of Physics.

Authors
Davis, JC; Warren, WS
MLA Citation
Davis, JC, and Warren, WS. "Selective excitation of high vibrational states using Raman chirped adiabatic passage." Journal of Chemical Physics 110.9 (1999): 4229-4237.
Source
scival
Published In
Journal of Chemical Physics
Volume
110
Issue
9
Publish Date
1999
Start Page
4229
End Page
4237

Altering excitation dynamics in optically dense media using shaped ultrafast laser pulses

Shaped pulses are routinely used in various applications to alter the excitation dynamics of atoms and molecules. In this context, the interaction between intense, shaped ultrafast laser pulses and optically dense samples of Rb vapor was investigated. Excited state Rb is interesting in its own right, as it is a key reagent in the preparation of the spin-polarized noble gases that are used in magnetic resonance imaging lung studies.

Authors
Davis, JC; Fetterman, MR; Goswami, D; Yang, WG; Keusters, D; Warren, WS
MLA Citation
Davis, JC, Fetterman, MR, Goswami, D, Yang, WG, Keusters, D, and Warren, WS. "Altering excitation dynamics in optically dense media using shaped ultrafast laser pulses." IQEC, International Quantum Electronics Conference Proceedings (1999): 107-108.
Source
scival
Published In
IQEC, International Quantum Electronics Conference Proceedings
Publish Date
1999
Start Page
107
End Page
108

Propagation of complex laser pulses in optically dense media

Optically dense rubidium vapor was excited using picosecond laser pulses. Effects such as pulse reshaping, self-focusing and stimulated emission are observed when shaped laser pulses propagated through the rubidium vapor. The pulse shapers, sech+, sech- and Gaussian pulses, can control the pulse reshaping in the atomic rubidium, thereby exciting the atomic system in different fashions.

Authors
Fetterman, MR; Davis, JC; Goswami, D; Yang, W; Warren, WS
MLA Citation
Fetterman, MR, Davis, JC, Goswami, D, Yang, W, and Warren, WS. "Propagation of complex laser pulses in optically dense media." Physical Review Letters 82.20 (1999): 3984-3987.
Source
scival
Published In
Physical Review Letters
Volume
82
Issue
20
Publish Date
1999
Start Page
3984
End Page
3987

MR imaging contrast enhancement based on intermolecular zero quantum coherences

A new method for magnetic resonance imaging (MRI) based on the detection of relatively strong signal from intermolecular zero-quantum coherences (iZQCs) is reported. Such a signal would not be observable in the conventional framework of magnetic resonance; it originates in long-range dipolar couplings (10 micrometers to 1 millimeter) that are traditionally ignored. Unlike conventional MRI, where image contrast is based on variations in spin density and relaxation times (often with injected contrast agents), contrast with iZQC images comes from variations in the susceptibility over a distance dictated by gradient strength. Phantom and in vivo (rat brain) data confirm that iZQC images give contrast enhancement. This contrast might be useful in the detection of small tumors, in that susceptibility correlates with oxygen concentration and in functional MRI.

Authors
Warren, WS; Ahn, S; Mescher, M; Garwood, M; Ugurbil, K; Richter, W; Rizi, RR; Hopkins, J; Leigh, JS
MLA Citation
Warren, WS, Ahn, S, Mescher, M, Garwood, M, Ugurbil, K, Richter, W, Rizi, RR, Hopkins, J, and Leigh, JS. "MR imaging contrast enhancement based on intermolecular zero quantum coherences." Science 281.5374 (1998): 247-251.
PMID
9657717
Source
scival
Published In
Science
Volume
281
Issue
5374
Publish Date
1998
Start Page
247
End Page
251
DOI
10.1126/science.281.5374.247

Ultrafast pulse shaping: Amplification and characterization

We demonstrate high-resolution amplified pulse shaping using an acousto-optic modulator (AOM) at a center-wavelength of 795nm. The output pulses have energy of 200μJ/pulse and a transform-limited pulsewidth of 150fs. A spectral modulation of over 40 features is achieved in a single pulse. We characterize the pulses using the STRUT (Spectrally and Temporally Resolved Upconversion Technique). Using predistortion techniques, we demonstrate that the pulses can be shaped in amplitude and phase. We create a complex pulse shape with hyperbolic secant amplitude and hyperbolic tangent frequency sweep, which is useful for applications in adiabatic rapid passage experiments. © 1998 Optical Society of America.

Authors
Fetterman, MR; Goswami, D; Keusters, D; Yang, W; Warren, WS
MLA Citation
Fetterman, MR, Goswami, D, Keusters, D, Yang, W, and Warren, WS. "Ultrafast pulse shaping: Amplification and characterization." Optics Express 3.10 (1998): 366-375.
Source
scival
Published In
Optics express
Volume
3
Issue
10
Publish Date
1998
Start Page
366
End Page
375

Intermolecular Zero-Quantum Coherences of Multi-component Spin Systems in Solution NMR

Intermolecular zero-quantum coherences (iZQC) induced by the dipolar demagnetizing field can give both P- and N-type cross peaks. This paper shows that the relative intensities of the two types of iZQC peaks follow a simple relation, tan2 (θ/2), from both the quantum (spin density matrix) and classical (modified Bloch equation) calculations. The experimental data and numerical simulations agree well with the prediction. In addition, higher-order iZQCs are experimentally examined for the first time and are explained by the quantum picture in which dipolar couplings convert four-spin operators into observable magnetization. © 1998 Academic Press.

Authors
Ahn, S; Lisitza, N; Warren, WS
MLA Citation
Ahn, S, Lisitza, N, and Warren, WS. "Intermolecular Zero-Quantum Coherences of Multi-component Spin Systems in Solution NMR." Journal of Magnetic Resonance 133.2 (1998): 266-272.
Source
scival
Published In
Journal of Magnetic Resonance
Volume
133
Issue
2
Publish Date
1998
Start Page
266
End Page
272

Effects of intermolecular dipolar couplings in solution NMR in separated time intervals: The competition for coherence transfer pathways

We investigate the competition between intermolecular dipolar effects in multiple time intervals and develop a theoretical framework to understand coherence transfer when this competition is important. The quantum picture permits explicit evaluation of coherence transfer pathways, which have been verified by experimental data obtained from pulse sequences with multiple-quantum selective phase cycling. Implications for sequences in common use in biological applications are discussed.

Authors
Ahn, S; Warren, WS
MLA Citation
Ahn, S, and Warren, WS. "Effects of intermolecular dipolar couplings in solution NMR in separated time intervals: The competition for coherence transfer pathways." Chemical Physics Letters 291.1-2 (1998): 121-129.
Source
scival
Published In
Chemical Physics Letters
Volume
291
Issue
1-2
Publish Date
1998
Start Page
121
End Page
129

Rethinking solution NMR

Authors
Warren, WS
MLA Citation
Warren, WS. "Rethinking solution NMR." Science 280.5362 (1998): 398-399.
Source
scival
Published In
Science
Volume
280
Issue
5362
Publish Date
1998
Start Page
398
End Page
399
DOI
10.1126/science.280.5362.398

Laser enhanced NMR spectroscopy, revisited

Experimental investigations of the effects of moderately powerful (10-20 W cm-2) off-resonant continuous lasers on NMR spectra provide no evidence for the B(3) field recently proposed, or for any other mechanism which depends on the light polarization. Observed 1H and 13C line shifts with argon-ion laser irradiation for the molecule p-methoxyphenyliminocamphor mostly can be explained by heating effects. Residual shifts due to other mechanisms appear to be at most 0·1 Hz (5% of the linewidth). One mechanism which could account for residual shifts of this magnitude is differences between NMR frequencies in the excited (triplet) and ground electronic states, although our data have insufficient resolution to make definitive claims. However, it seems unlikely that this effect can be made sufficiently large to give practical resolution enhancements without massive heating.

Authors
Warren, WS; Goswami, D; Mayr, S
MLA Citation
Warren, WS, Goswami, D, and Mayr, S. "Laser enhanced NMR spectroscopy, revisited." Molecular Physics 93.3 (1998): 371-375.
Source
scival
Published In
Molecular Physics
Volume
93
Issue
3
Publish Date
1998
Start Page
371
End Page
375

Feedback quantum control of population transfer using shaped femtosecond pulses

Quantum control is extended to complex molecular systems by using experimental feedback to control the acousto-optic tailoring of ultrashort pulses.

Authors
Bardeen, C; Yakovlev, VV; Wilson, KR; Carpenter, SD; Weber, PM; Warren, WS
MLA Citation
Bardeen, C, Yakovlev, VV, Wilson, KR, Carpenter, SD, Weber, PM, and Warren, WS. "Feedback quantum control of population transfer using shaped femtosecond pulses." Springer Series in Chemical Physics 63 (1998): 645-647.
Source
scival
Published In
Springer Series in Chemical Physics
Volume
63
Publish Date
1998
Start Page
645
End Page
647

Generation of amplified shaped pulses for highly adiabatic excitation

Complex amplified pulses, including a 1 ps, 100 μJ tanh-swept sech pulse for adiabatic inversion, are generated experimentally. STRUT detection verifies the modulation and follows the dynamics induced by such pulses in Rb vapor. Applications to production of spin-polarized gases for medical imaging are discussed.

Authors
Fetterman, M; Goswami, D; Keusters, D; Rhee, J-K; Warren, WS
MLA Citation
Fetterman, M, Goswami, D, Keusters, D, Rhee, J-K, and Warren, WS. "Generation of amplified shaped pulses for highly adiabatic excitation." Springer Series in Chemical Physics 63 (1998): 24-26.
Source
scival
Published In
Springer Series in Chemical Physics
Volume
63
Publish Date
1998
Start Page
24
End Page
26

The boundary between liquidlike and solidlike behavior in magnetic resonance

Recent experimental work in two-dimensional solution NMR (nuclear magnetic resonance) has demonstrated anomalous cross-peaks and additional resonances due to dipolar couplings between distant nuclei. These spectra have been analyzed either classically, using Bloch equations which include a mean-field approximation to the demagnetizing field, or quantum mechanically, using a full density matrix picture which shows that the peaks correspond to intermolecular multiple-quantum coherences (iMQCs). Here we use a density matrix treatment to predict intensities in solution for dipolar effects conventionally seen in solids; we also explore in detail the fundamental differences between dipolar effects in solids and liquids. For example, even though polarization transfer via the dipolar Hamiltonian in solution is not possible, indirect detection with substantial signal enhancement is possible. We find that, even for high-γ nuclei such as 1H or 3He, solidlike dipolar effects are quite small unless the diffusion constant is roughly one million times smaller than that of water - which means that deviations between the quantum and classical treatments are barely observable in solution NMR, and that even solid 3He has liquidlike dipolar effects in agreement with experiment. However, the dipolar correlation function has an extremely unusual functional form - the long time falloff is proportional to t-3/2, not the exponential one commonly encounters. Because of this long falloff, solidlike dipolar effects can be substantial in solution electron spin resonance, and the classical picture of the demagnetizing field would fail in that case. © 1998 American Institute of Physics.

Authors
Warren, WS; Ahn, S
MLA Citation
Warren, WS, and Ahn, S. "The boundary between liquidlike and solidlike behavior in magnetic resonance." Journal of Chemical Physics 108.4 (1998): 1313-1325.
Source
scival
Published In
Journal of Chemical Physics
Volume
108
Issue
4
Publish Date
1998
Start Page
1313
End Page
1325

Optical wavelength domain code-division multiplexing using an AOM-based ultrafast optical pulse shaping approach

Optical wavelength domain code-division multiplexing access (WD-CDMA) using an AOM-based ultrafast optical pulse shaping approach is proposed and demonstrated experimentally at 1550 nm. This new multiplexing technique utilizes wavelength domain codes that are essentially different optical spectral patterns in order to achieve CDMA. In addition to the advantages of the conventional CDMA technique, WD-CDMA can make full use of the entire optical bandwidth without requiring faster optical switches or modulators. This approach also drastically reduces sensitivity to fiber dispersion. Experimentally, we demonstrate an optical spectral encoder using ultrafast optical pulse shaping with 16 wavelength bits over an optical bandwidth of 5 THz. The spectrally-encoded optical pulse generated with the spectral encoder is then decoded with different WD-CDMA codes in the spectral domain. Different code-division channels can thus extract their own bit information while sharing the same spectral-encoded laser pulse as their common carrier. These spectral-encoded pulses are shown using the cross-correlation technique to be confined within a time slot of 15 ps. A larger number of WD bits is also achievable with our system.

Authors
Yang, W; Davis, J; Goswami, D; Fetterman, M; Warren, WS
MLA Citation
Yang, W, Davis, J, Goswami, D, Fetterman, M, and Warren, WS. "Optical wavelength domain code-division multiplexing using an AOM-based ultrafast optical pulse shaping approach." Proceedings of SPIE - The International Society for Optical Engineering 3531 (1998): 80-86.
Source
scival
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
3531
Publish Date
1998
Start Page
80
End Page
86

New ways to observe and control dynamics

We summarize recent progress aimed at observing biochemical and biological dynamics using confocal microscopy with 3D spatial resolution down to a few hundred nm and temporal resolution to 15 fs. We also review recent control of population dynamics using tailored ultrafast pulses, i.e. quantum control. Progress is described for i) feedback control, ii) multiphoton control, and iii) molecular π pulse. Finally, using ultrafast light pulses, we combine confocal and quantum control techniques to produce a new way to measure the microscopic chemical environment, in this case pH, potentially with a spatial resolution of a few hundred nanometers.

Authors
Wilson, KR; Bardeen, C; Barty, CPJ; Brakenhoff, GJ; Buist, AH; Cao, J; Carpenter, SD; Che, J; Fittinghoff, DN; Müller, M; Squier, JA; Warren, WS; Weber, PM; Yakovlev, VV
MLA Citation
Wilson, KR, Bardeen, C, Barty, CPJ, Brakenhoff, GJ, Buist, AH, Cao, J, Carpenter, SD, Che, J, Fittinghoff, DN, Müller, M, Squier, JA, Warren, WS, Weber, PM, and Yakovlev, VV. "New ways to observe and control dynamics." Proceedings of SPIE - The International Society for Optical Engineering 3273 (1998): 214-218.
Source
scival
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
3273
Publish Date
1998
Start Page
214
End Page
218
DOI
10.1117/12.306130

New tricks in quantum control

Quantum control involving multiple interactions with light of different colors within the same light pulse is analyzed. Experiments on I2 have demonstrated up to a 300% enhancement of the multiphoton yield with the appropriately chirped pulse. Such multiphoton control can be the basis of the molecular `π pulse,' capable of inverting the entire electronic ground state population of a molecule to an excited electronic state. This multiphoton quantum control is applied to produce a new class of molecular reporter system for ultrafast measurement of the molecular scale chemical environment, and is used to measure the pH from the fluorescence intensity ratio for positive and negative chirped pulses.

Authors
Wilson, KR; Bardeen, CJ; Brakenhoff, GJ; Buist, A; Cao, J; Carpenter, SD; Che, J; Squier, JA; Warren, WS; Weber, PM; Yakovlev, VV
MLA Citation
Wilson, KR, Bardeen, CJ, Brakenhoff, GJ, Buist, A, Cao, J, Carpenter, SD, Che, J, Squier, JA, Warren, WS, Weber, PM, and Yakovlev, VV. "New tricks in quantum control." Technical Digest - European Quantum Electronics Conference (1998): 3--.
Source
scival
Published In
Technical Digest - European Quantum Electronics Conference
Publish Date
1998
Start Page
3-

The competition between intramolecular J couplings, radiation damping, and intermolecular dipolar couplings in two-dimensional solution nuclear magnetic resonance

Scalar couplings have long been used to observe forbidden transitions indirectly, e.g., the multiple-quantum transitions detected frequently in the indirect dimension of multidimensional NMR experiments. Recent work has shown that intermolecular dipolar couplings in solution will also permit the detection of multiple-quantum coherences, this time between separated spins (intermolecular multiple-quantum coherences, iMQCs). Analytical expressions are derived to describe spin evolution for an essentially arbitrarily complex coupled spin system when dipolar couplings or radiation damping also are significant. The results are tested on an A2B3+Cn system (methyl ethyl ketone). iMQCs that are forbidden from radiation damping or dipolar couplings alone can become allowed in the presence of J couplings, but the multiplet patterns differ dramatically from conventional multiplets. Scalar couplings open up new pathways for pumping the normally allowed transitions.

Authors
Ahn, S; Lee, S; Warren, WS
MLA Citation
Ahn, S, Lee, S, and Warren, WS. "The competition between intramolecular J couplings, radiation damping, and intermolecular dipolar couplings in two-dimensional solution nuclear magnetic resonance." Molecular Physics 95.5 (1998): 769-785.
Source
scival
Published In
Molecular Physics
Volume
95
Issue
5
Publish Date
1998
Start Page
769
End Page
785

Rapid ultrafine-tunable optical delay line at the 1.55-μm wavelength

A fast, ultrafine-tunable delay line at 1550 nm is demonstrated by use of acousto-optic pulse shaping. Delays of up to 30 ps can be achieved without any optical readjustment. The delay is linear to the rf center frequency applied to the acousto-optic modulator and is fully electronic. It takes only 3 μm to switch between different time slots, irrespective of the time separation in the tuning range of 30 ps; for a smaller tuning range the tuning speed can be faster. The tuning resolution and range depend on the choice of system parameters. The pulse energy can be regulated by rf power. © 1998 Optical Society of America.

Authors
Yang, W; Keusters, D; Goswami, D; Warren, WS
MLA Citation
Yang, W, Keusters, D, Goswami, D, and Warren, WS. "Rapid ultrafine-tunable optical delay line at the 1.55-μm wavelength." Optics Letters 23.23 (1998): 1843-1845.
Source
scival
Published In
Optics Letters
Volume
23
Issue
23
Publish Date
1998
Start Page
1843
End Page
1845

Optical frequency domain differential phase shift keying in femtosecond-pulse spectral modulation systems

We propose a novel scheme of differential phase shift keying (DPSK) in the optical frequency domain. We take advantage of the intrinsic coherence among spectral elements derived by spectrum slicing a femtosecond optical pulse, introducing differential phase modulation between adjacent spectral elements with a femtosecond-pulse shaper. Detection of the differential phase is achieved by a Mach-Zehnder (MZ) or Sagnac interferometric receiver without requirement of any external phase reference.

Authors
Rhee, J-K; Kobayashi, H; Warren, WS
MLA Citation
Rhee, J-K, Kobayashi, H, and Warren, WS. "Optical frequency domain differential phase shift keying in femtosecond-pulse spectral modulation systems." Journal of Lightwave Technology 15.12 (1997): 2214-2222.
Source
scival
Published In
Journal of Lightwave Technology
Volume
15
Issue
12
Publish Date
1997
Start Page
2214
End Page
2222
DOI
10.1109/50.643543

Quantum Treatment of Intermolecular Multiple-Quantum Coherences with Intramolecular J Coupling in Solution NMR

A recently introduced density matrix picture for dipolar effects in solution NMR (1996, J. Chem. Phys. 105, 874) gave complete solutions for intermolecular multiple-quantum coherences for single-component samples without scalar couplings. This paper, for the first time, shows that this quantum picture can lead to explicit signal expressions for multicomponent samples of molecules with internal scalar couplings (here assumed to generate a first-order spectrum) and long-range dipolar couplings. Experimental observation of a triplet in the indirectly detected dimension for a heteronuclear CRAZED sequence (13CHCl3 sample, ZQ or 2Q coherences) gives clear evidence that the coupling is due to the intermolecular dipolar coupling. We also make comparisons with classical pictures which introduce the dipolar demagnetization field in multicomponent spin systems. © 1997 Academic Press.

Authors
Ahn, S; Warren, WS; Lee, S
MLA Citation
Ahn, S, Warren, WS, and Lee, S. "Quantum Treatment of Intermolecular Multiple-Quantum Coherences with Intramolecular J Coupling in Solution NMR." Journal of Magnetic Resonance 128.2 (1997): 114-129.
PMID
9356265
Source
scival
Published In
Journal of Magnetic Resonance
Volume
128
Issue
2
Publish Date
1997
Start Page
114
End Page
129

Feedback quantum control of molecular electronic population transfer

Feedback quantum control, where the sample 'teaches' a computer-controlled arbitrary lightform generator to find the optimal light field, is experimentally demonstrated for a molecular system. Femtosecond pulses tailored by a computer-controlled acousto-optic pulse shaper excite fluorescence from laser dye molecules in solution. Fluorescence and laser power are monitored, and the computer uses the experimental data and a genetic algorithm to optimize population transfer from ground to first excited state. Both efficiency (the ratio of excited state population to laser energy) and effectiveness (total excited state population) are optimized. Potential use as an 'automated theory tester' is discussed.

Authors
Bardeen, CJ; Yakovlev, VV; Wilson, KR; Carpenter, SD; Weber, PM; Warren, WS
MLA Citation
Bardeen, CJ, Yakovlev, VV, Wilson, KR, Carpenter, SD, Weber, PM, and Warren, WS. "Feedback quantum control of molecular electronic population transfer." Chemical Physics Letters 280.1-2 (1997): 151-158.
Source
scival
Published In
Chemical Physics Letters
Volume
280
Issue
1-2
Publish Date
1997
Start Page
151
End Page
158

High-resolution acousto-optic shaping of unamplified and amplified femtosecond laser pulses

We focus theoretically and experimentally on the fundamental limitations of spectral pulse shaping using an acousto-optic modulator. We analyze the role of the relative thickness of the interaction region as dictated by the acousto-optic Q parameter and show that varying Q allows flexibility in choosing between diffraction efficiency and pixels of resolution. We model and experimentally demonstrate the effects of potential nonidealities such as nonlinear acoustic attenuation. In addition, we derive a simple and intuitive expression to predict the magnitude of the distortions in the spatial profile generated by an acousto-optic-modulator spectral light modulator. Finally, we demonstrate amplification of acousto-optic-modulator-generated shaped pulses for the first time. © 1997 Optical Society of America.

Authors
Dugan, MA; Tull, JX; Warren, WS
MLA Citation
Dugan, MA, Tull, JX, and Warren, WS. "High-resolution acousto-optic shaping of unamplified and amplified femtosecond laser pulses." Journal of the Optical Society of America B: Optical Physics 14.9 (1997): 2348-2358.
Source
scival
Published In
Journal of the Optical Society of America B
Volume
14
Issue
9
Publish Date
1997
Start Page
2348
End Page
2358

High-resolution, ultrafast laser pulse shaping and its applications

Authors
Tull, JX; Dugan, MA; Warren, WS
MLA Citation
Tull, JX, Dugan, MA, and Warren, WS. "High-resolution, ultrafast laser pulse shaping and its applications." Advances in Magnetic and Optical Resonance 20.C (1997): 1-II.
Source
scival
Published In
Advances in Magnetic and Optical Resonance
Volume
20
Issue
C
Publish Date
1997
Start Page
1
End Page
II
DOI
10.1016/S1057-2732(97)80002-2

A terabit-per-second network with the spectral-domain modulation

We discuss an architecture and underlying technologies of terabit-per-second network with the spectral-domain modulation. The baseline architecture is TDM which exploits our techniques for imposing > 1000 pixel phase and amplitude modulation on the spectrum of a 100 fs laser pulse, using microsecond radiofrequency pulse trains, for all-optical demultiplexing to efficiently select 100 fs-100 ps time slices. The network architectures we will initially explore is a single-hop star network that uses an active star coupler as a shared medium. We will also explore a WDM/TDM network with a waveguide grating router as its hub.

Authors
Kobayashi, H; Prucnal, PR; Warren, WS
MLA Citation
Kobayashi, H, Prucnal, PR, and Warren, WS. "A terabit-per-second network with the spectral-domain modulation." Proceedings of SPIE - The International Society for Optical Engineering 3231 (1997): 75-86.
Source
scival
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
3231
Publish Date
1997
Start Page
75
End Page
86
DOI
10.1117/12.290449

The usefulness of NMR quantum computing

Authors
Warren, WS; Gershenfeld, N; Chuang, I
MLA Citation
Warren, WS, Gershenfeld, N, and Chuang, I. "The usefulness of NMR quantum computing." Science 277.5332 (1997): 1688-1690.
Source
scival
Published In
Science
Volume
277
Issue
5332
Publish Date
1997
Start Page
1688
End Page
1690
DOI
10.1126/science.277.5332.1688

Quantum treatment of the effects of dipole-dipole interactions in liquid nuclear magnetic resonance

Experimental observation of anomalous intermolecular cross-peaks in two-dimensional solution NMR spectra have attracted significant recent attention. Extremely simple pulse sequences on extremely simple samples with large equilibrium magnetization give resonances in the indirectly detected dimension which are simply impossible in the conventional density matrix framework of NMR. Here we extend a recently proposed density matrix treatment [Science 262, 2005 (1993)] to calculate the exact time evolution for a variety of pulse sequences. This density matrix treatment explicitly removes two fundamental assumptions of the standard theory - it includes the dipolar interaction between spins in solution (which is only partially averaged away by diffusion) and completely removes the high temperature approximation to the equilibrium density matrix [exp(-βℋ)≈1-βℋ]. We compare this quantum mechanical treatment to a corrected classical model, which modifies the dipolar demagnetizing field formulation to account for the effects of residual magnetization, and show that the quantum picture can be reduced to this corrected classical model when certain assumptions about the retained dipolar couplings are valid. The combination of quantum and classical pictures provides enormously better predictive power and computational convenience than either technique alone. © 1996 American Institute of Physics.

Authors
Lee, S; Richter, W; Vathyam, S; Warren, WS
MLA Citation
Lee, S, Richter, W, Vathyam, S, and Warren, WS. "Quantum treatment of the effects of dipole-dipole interactions in liquid nuclear magnetic resonance." Journal of Chemical Physics 105.3 (1996): 874-900.
Source
scival
Published In
Journal of Chemical Physics
Volume
105
Issue
3
Publish Date
1996
Start Page
874
End Page
900

Homogeneous NMR spectra in inhomogeneous fields

Researchers interested in high-resolution nuclear magnetic resonance (NMR) spectroscopy have long sought higher magnetic fields to enhance resolution and simplify spectra. Magnets with substantially larger fields than those available in the best commercial spectrometers are available, but the inhomogeneity is unacceptable for high-resolution spectra. A detection method (termed HOMOGENIZED) is presented that removes inhomogeneity while retaining chemical shift differences and J couplings. With existing inhomogeneous magnets, this method could nearly doublethe largest resonance frequency available for high-resolution NMR. The HOMOGENIZED sequence is based on observations of intermolecular zero-quantum coherences between a solute molecule and solvent molecules that are micrometers away; as long as the field is homogeneous over this short distance, sharp resonances are recovered without echoes. Experimental demonstrations and a detailed density matrix theory to explain the effect are presented.

Authors
Vathyam, S; Lee, S; Warren, WS
MLA Citation
Vathyam, S, Lee, S, and Warren, WS. "Homogeneous NMR spectra in inhomogeneous fields." Science 272.5258 (1996): 92-96.
PMID
8600541
Source
scival
Published In
Science
Volume
272
Issue
5258
Publish Date
1996
Start Page
92
End Page
96

Minimizing the water resonance in biological NMR: Characterization and suppression of intermolecular dipolar interactions by multiple-axis gradients

Anomalous crosspeaks and additional resonances in the indirectly detected dimension have been previously observed in a number of 2D NMR experiments applied to samples having at least one concentrated species. These unexpected peaks exhibit all the characteristics of intermolecular multiple-quantum coherences. Since these coherences are possible within the concentrated species alone, their creation and subsequent detection may be one of the causes for poor water suppression in a variety of biomolecular NMR experiments, e.g., the conventional MQ-filtered-(MQF) and MQ-COSY experiments applied to proteins/peptides in 90% water. In this report, we experimentally characterize the creation/observation of intermolecular water-water MQ coherences using variable-angle pulsed field gradients. We show that the existing theoretical picture is consistent with all of our experimental observations, thereby validating the predictive power of the intuition gained from this picture. We also provide an increased understanding of the effect that variable-angle gradients can have on the intensity of observable magnetization arising from these intermolecular MQ coherences. Finally, we establish a basis on which one may reasonably speculate concerning the impact of these coherences on water suppression within the repertoire of gradient-enhanced heteronuclear experiments that are currently being applied to 13C/15N isotopically labeled proteins in 90% water.

Authors
Mattiello, DL; Warren, WS; Mueller, L; II, BTF
MLA Citation
Mattiello, DL, Warren, WS, Mueller, L, and II, BTF. "Minimizing the water resonance in biological NMR: Characterization and suppression of intermolecular dipolar interactions by multiple-axis gradients." Journal of the American Chemical Society 118.13 (1996): 3253-3261.
Source
scival
Published In
Journal of the American Chemical Society
Volume
118
Issue
13
Publish Date
1996
Start Page
3253
End Page
3261
DOI
10.1021/ja953186o

Detection of intermolecular heteronuclear multiple-quantum coherences in solution NMR

Authors
Bachiller, PR; Ahn, S; Warren, WS
MLA Citation
Bachiller, PR, Ahn, S, and Warren, WS. "Detection of intermolecular heteronuclear multiple-quantum coherences in solution NMR." Journal of Magnetic Resonance - Series A 122.1 (1996): 94-99.
Source
scival
Published In
Journal of Magnetic Resonance - Series A
Volume
122
Issue
1
Publish Date
1996
Start Page
94
End Page
99

High-resolution ultrafast laser pulse shaping for quantum control and terabit per second communications

High resolution (≈ 1000 pixels), rapidly updatable fs laser pulse shaping permits a terabit per second communications architecture and quantum control.

Authors
Dugan, M; Tull, JX; Ree, J-K; Warren, WS
MLA Citation
Dugan, M, Tull, JX, Ree, J-K, and Warren, WS. "High-resolution ultrafast laser pulse shaping for quantum control and terabit per second communications." Springer Series in Chemical Physics 62 (1996): 26-27.
Source
scival
Published In
Springer Series in Chemical Physics
Volume
62
Publish Date
1996
Start Page
26
End Page
27

Correcting the classical dipolar demagnetizing field in solution NMR

Numerous observations of anomalous intermolecular multiple-quantum and cross correlation peaks in solution NMR have led to a variety of theoretical treatments, some involving radiation damping or modified classical Bloch equations, others involving full quantum mechanical derivations. We explore the theoretical underpinnings of the classical model, which invokes the dipolar demagnetizing field, and correct a significant omission in the original formulation which has been propagated in later papers. This correction gives good agreement between theory and experiment. © 1995.

Authors
Warren, WS; Lee, S; Richter, W; Vathyam, S
MLA Citation
Warren, WS, Lee, S, Richter, W, and Vathyam, S. "Correcting the classical dipolar demagnetizing field in solution NMR." Chemical Physics Letters 247.3 (1995): 207-214.
Source
scival
Published In
Chemical Physics Letters
Volume
247
Issue
3
Publish Date
1995
Start Page
207
End Page
214
DOI
10.1016/0009-2614(95)01184-5

Imaging with intermolecular multiple-quantum coherences in solution nuclear magnetic resonance

A magnetic resonance imaging technique based on intermolecular multiple-quantum coherences in solution (the correlated spectroscopy revamped by asymmetric z gradient echo detection or CRAZED experiment) is described here. Correlations between spins in different molecules were detected by magnetic-field gradient pulses. In order for a correlation to yield an observable signal, the separation between the two spins must be within a narrow band that depends on the area of the gradient pulses. The separation can be tuned from less than 10 micrometers to more than 1 millimeter, a convenient range for many applications.

Authors
Richter, W; Lee, S; Warren, WS; He, Q
MLA Citation
Richter, W, Lee, S, Warren, WS, and He, Q. "Imaging with intermolecular multiple-quantum coherences in solution nuclear magnetic resonance." Science 267.5198 (1995): 654-657.
PMID
7839140
Source
scival
Published In
Science
Volume
267
Issue
5198
Publish Date
1995
Start Page
654
End Page
657

Erratum: Adiabatic population transfer with frequency swept laser pulses (The Journal of Chemical Physics (1994) 101 (6439))

Authors
Melinger, JS; Gandhi, SR; Hariharan, A; Goswami, D; Warren, WS
MLA Citation
Melinger, JS, Gandhi, SR, Hariharan, A, Goswami, D, and Warren, WS. "Erratum: Adiabatic population transfer with frequency swept laser pulses (The Journal of Chemical Physics (1994) 101 (6439))." The Journal of Chemical Physics 102.13 (1995): 5574--.
Source
scival
Published In
Journal of Chemical Physics
Volume
102
Issue
13
Publish Date
1995
Start Page
5574-

Selective excitation of vibrational overtones in an anharmonic ladder with frequency- and amplitude-modulated laser pulses

We show numerically that the complex hyperbolic secant pulse provides robust selective inversion of vibrational overtones. A density-matrix analysis is performed for a ten-level Morse-oscillator approximation of a diatomic molecule. We also show that in the limit of adiabatic excitation the complex-hyperbolic-secant pulse yields an inversion spectrum that is narrower than its spectral bandwidth. © 1995 The American Physical Society.

Authors
Melinger, JS; McMorrow, D; Hillegas, C; Warren, WS
MLA Citation
Melinger, JS, McMorrow, D, Hillegas, C, and Warren, WS. "Selective excitation of vibrational overtones in an anharmonic ladder with frequency- and amplitude-modulated laser pulses." Physical Review A 51.4 (1995): 3366-3369.
Source
scival
Published In
Physical Review A - Atomic, Molecular, and Optical Physics
Volume
51
Issue
4
Publish Date
1995
Start Page
3366
End Page
3369
DOI
10.1103/PhysRevA.51.3366

Femtosecond laser pulse shaping by use of microsecond radio-frequency pulses

In this paper, a method for modulating femtosecond pulses was presented, using microsecond rf pulses in an acousto-optic modulator (AOM). It was demonstrated that an AOM at the line focus of a zero-dispersion grating pair furnished convenient and powerful capabilities for femtosecond pulse shaping. In comparison with current methods, this approach has the advantages of faster update times, no pixel gaps, high isolation, and simple calibration. It was also better suited for application with existing commercial components. Experimental data were provided that exhibited effective modulation and discussed the possible ultimate capacities and limitations.

Authors
Hillegas, CW; Tull, JX; Goswami, D; Strickland, D; Warren, WS
MLA Citation
Hillegas, CW, Tull, JX, Goswami, D, Strickland, D, and Warren, WS. "Femtosecond laser pulse shaping by use of microsecond radio-frequency pulses." Optics Letters 19.10 (1994): 737-739.
Source
scival
Published In
Optics Letters
Volume
19
Issue
10
Publish Date
1994
Start Page
737
End Page
739

Adiabatic population transfer with frequency-swept laser pulses

The application of frequency-swept picosecond laser pulses in achieving efficient population transfer via adiabatic rapid passage (ARP) was described. The basic theoretical considerations useful for understanding ARP in both few-level and multi-level systems were presented. A detailed report of the experimental arrangement and methods used to generate frequency-swept laser pulses was also provided. The results of coherent population transfer experiments on solid phase and vapor phase systems were presented and compared to theoretical calculations on model systems. It was determined that the frequency sweep of the laser pulse need not necessarily be linear, nor even monotonic. Selective excitation and enhanced population will surely occur provided the conditions for ARP are well satisfied.

Authors
Melinger, JS; Gandhi, SR; Hariharan, A; Goswami, D; Warren, WS
MLA Citation
Melinger, JS, Gandhi, SR, Hariharan, A, Goswami, D, and Warren, WS. "Adiabatic population transfer with frequency-swept laser pulses." Journal of Chemical Physics 101.8 (1994): 6439-6454.
Source
scival
Published In
Journal of Chemical Physics
Volume
101
Issue
8
Publish Date
1994
Start Page
6439
End Page
6454
DOI
10.1063/1.468368

Effects of pulses with simple phase and frequency modulations

The effects of pulse shapes with simple phase and frequency modulation (phase proportional to amplitude or intensity, frequency proportional to intensity) are explored numerically. Many such shapes can be generated by combining self-phase-modulation with modern laser pulse-shaping capabilities (which are more flexible for amplitude modulation than for frequency modulation). Even though all of these wave forms begin and end at the same frequency (and hence violate the mathematical conditions for adiabatic inversion), we show that they can generate adiabatic population inversion or suppress intramolecular energy redistribution. © 1994 The American Physical Society.

Authors
Goswami, D; Warren, WS
MLA Citation
Goswami, D, and Warren, WS. "Effects of pulses with simple phase and frequency modulations." Physical Review A 50.6 (1994): 5190-5196.
Source
scival
Published In
Physical Review A - Atomic, Molecular, and Optical Physics
Volume
50
Issue
6
Publish Date
1994
Start Page
5190
End Page
5196
DOI
10.1103/PhysRevA.50.5190

Generation of impossible cross-peaks between bulk water and biomolecules in solution NMR

Intermolecular multiple-quantum coherences between bulk water and a glycoprotein fragment at modest concentration (20 mM) have been experimentally produced and detected, although such coherences are inconceivable in the normal theoretical framework of nuclear magnetic resonance. A density matrix treatment explains these results by including the long-range dipolar interaction between spins and by discarding the high-temperature approximation. These results imply that peak intensities (critical for structural determinations) can be distorted in many gradient experiments, and show that magic-angle gradients provide substantial improvements with reduced gradient strengths. They also suggest methods for contrast enhancement in magnetic resonance imaging.

Authors
Warren, WS; Richter, W; Andreotti, AH; II, BTF
MLA Citation
Warren, WS, Richter, W, Andreotti, AH, and II, BTF. "Generation of impossible cross-peaks between bulk water and biomolecules in solution NMR." Science 262.5142 (1993): 2005-2009.
PMID
8266096
Source
scival
Published In
Science
Volume
262
Issue
5142
Publish Date
1993
Start Page
2005
End Page
2009

Coherent control of quantum dynamics: The dream is alive

Current experimental and theoretical progress toward the goal of controlling quantum dynamics is summarized. Two key developments have now revitalized the field. First, appropriate ultrafast laser pulse shaping capabilities have only recently become practical. Second, the introduction of engineering control concepts has put the required theoretical framework on a rigorous foundation. Extrapolations to determine what is realistically possible are presented.

Authors
Warren, WS; Rabitz, H; Dahleh, M
MLA Citation
Warren, WS, Rabitz, H, and Dahleh, M. "Coherent control of quantum dynamics: The dream is alive." Science 259.5101 (1993): 1581-1589.
Source
scival
Published In
Science
Volume
259
Issue
5101
Publish Date
1993
Start Page
1581
End Page
1589

Intermolecular multiple-quantum coherences and cross correlations in solution nuclear magnetic resonance

It was recently reported that multiple-quantum NMR coherences could apparently be observed in water and other concentrated samples, in direct violation of established theory. These results were previously explained in a dressed-state framework as manifestations of the coupling between the spins and the coil (quantized radiation damping). Here we provide details of previously communicated experimental explorations of these effects [J. Chem. Phys. 96, 1659 (1992)], and we extend these results to multicomponent samples. We observe cross peaks between independent molecules in solution in two-dimensional experiments, including spectra with multiple-quantum coherence transfer echoes; we also demonstrate coherence transfer between solvent and (dilute) solute molecules. However, we show that these intermolecular cross peaks are induced by a mechanism which is local in nature, and thus radiation damping (either classical or quantized) cannot provide the bulk of the explanation for their occurrence. Simulations and analytical results show that the dipolar demagnetizing field can account for many of these surprising effects, although a complete picture must be more complex. © 1993 American Institute of Physics.

Authors
He, Q; Richter, W; Vathyam, S; Warren, WS
MLA Citation
He, Q, Richter, W, Vathyam, S, and Warren, WS. "Intermolecular multiple-quantum coherences and cross correlations in solution nuclear magnetic resonance." The Journal of Chemical Physics 98.9 (1993): 6779-6800.
Source
scival
Published In
Journal of Chemical Physics
Volume
98
Issue
9
Publish Date
1993
Start Page
6779
End Page
6800

Laser-enhanced NMR spectroscopy: Theoretical considerations

Authors
Warren, WS; Mayr, S; Goswami, D; Jr, APW
MLA Citation
Warren, WS, Mayr, S, Goswami, D, and Jr, APW. "Laser-enhanced NMR spectroscopy: Theoretical considerations." Science 259.5096 (1993): 836--.
Source
scival
Published In
Science
Volume
259
Issue
5096
Publish Date
1993
Start Page
836-

Chemistry with photons

Authors
Warren, WS
MLA Citation
Warren, WS. "Chemistry with photons." Science 262.5136 (1993): 1008-1009.
Source
scival
Published In
Science
Volume
262
Issue
5136
Publish Date
1993
Start Page
1008
End Page
1009

Laser-enhanced NMR spectroscopy: Theoretical considerations

Authors
Harris, RA; Jr, IT; Warren, WS; Mayr, S; Goswami, D; Jr, APW
MLA Citation
Harris, RA, Jr, IT, Warren, WS, Mayr, S, Goswami, D, and Jr, APW. "Laser-enhanced NMR spectroscopy: Theoretical considerations." Science 259.5096 (1993): 835-836.
Source
scival
Published In
Science
Volume
259
Issue
5096
Publish Date
1993
Start Page
835
End Page
836

Stimulated emission pumping and selective excitation by adiabatic passage with frequency-modulated picosecond laser pulses

We demonstrate that picosecond frequency modulated laser pulses produce more efficient population transfer, and more selective excitation than equivalent (same spectral width) nearly transform limited laser pulses. We also note the ″ robustness″, or insensitivity of the properties of the material excitation to the parameters of the laser field, that is inherent to the adiabatic process. The robustness obtainable by adiabatic passage may ultimately prove useful to laboratory applications of theoretical schemes for laser-control of chemical reaction dynamics.

Authors
Melinger, JS; Hariharan, A; Gandhi, SR; Warren, WS
MLA Citation
Melinger, JS, Hariharan, A, Gandhi, SR, and Warren, WS. "Stimulated emission pumping and selective excitation by adiabatic passage with frequency-modulated picosecond laser pulses." Springer Series in Chemical Physics 55 (1993): 113-115.
Source
scival
Published In
Springer Series in Chemical Physics
Issue
55
Publish Date
1993
Start Page
113
End Page
115

Control of chemical dynamics by restricting intramolecular vibrational relaxation

We address the issue of localization of bond energy in a molecule by stopping intramolecular vibrational relaxation (IVR). We show through model calculations that appropriate frequency sweeps permit selective locking over a well-defined range of resonance frequencies, with little excitation outside that range. We also propose a modified version of an adiabatic half passage experiment that will perform photon locking without complications from inhomogeneities or partial excitation of other transitions for a bright state coupled to a finite number of dark states. © 1993 American Institute of Physics.

Authors
Goswami, D; Warren, WS
MLA Citation
Goswami, D, and Warren, WS. "Control of chemical dynamics by restricting intramolecular vibrational relaxation." The Journal of Chemical Physics 99.6 (1993): 4509-4517.
Source
scival
Published In
Journal of Chemical Physics
Volume
99
Issue
6
Publish Date
1993
Start Page
4509
End Page
4517

Laser-enhanced NMR spectroscopy

Experimental studies show that optical irradation far from any absorption bands can shift the resonances in a nuclear magnetic resonance (NMR) spectrum without significant heating. This effect may lead to increased dispersion in NMR studies of complex molecules.

Authors
Warren, WS; Mayr, S; Goswami, D; Jr, APW
MLA Citation
Warren, WS, Mayr, S, Goswami, D, and Jr, APW. "Laser-enhanced NMR spectroscopy." Science 255.5052 (1992): 1683-1685.
PMID
1553555
Source
scival
Published In
Science
Volume
255
Issue
5052
Publish Date
1992
Start Page
1683
End Page
1685

Pulse shaping in quadrupole-echo NMR

Shaped radiofrequency pulses are designed to extend the quadrupole-echo excitation bandwidth without insidious phase distortions. The quadrupole-shaped pulse (QUASH) is constructed by a simple iterative optimization procedure which directly solves a density-matrix equation of motion for an arbitrary amplitude-modulated pulse acting on a three-level system. Computer simulations and experimental 2H NMR studies comparing the performance of simple rectangular, composite, and shaped quadrupole-echo sequences on the partially rotating methyl group on 1-alanine-d3,3,3 show a dramatic improvement using the shaped excitation pulse. Increases in the effective bandwidth by a factor of two and three were realized over composite and rectangular sequences, respectively, without phase distortions. © 1992.

Authors
McCoy, MA; Warren, WS
MLA Citation
McCoy, MA, and Warren, WS. "Pulse shaping in quadrupole-echo NMR." Journal of Magnetic Resonance (1969) 98.1 (1992): 24-35.
Source
scival
Published In
Journal of Magnetic Resonance (1969)
Volume
98
Issue
1
Publish Date
1992
Start Page
24
End Page
35

Testing the limits of shape optimization by large-flip-angle pulses

Optimized waveforms for inverting pulses with areas up to 9π are reported. Both differences and similarities in rectangularity of inversion and sensitivity to inhomogeneity are found. For some applications many-π pulses may be more useful than low-flip-angle pulses. © 1992.

Authors
McDonald, SD; Warren, WS
MLA Citation
McDonald, SD, and Warren, WS. "Testing the limits of shape optimization by large-flip-angle pulses." Journal of Magnetic Resonance (1969) 99.2 (1992): 282-291.
Source
scival
Published In
Journal of Magnetic Resonance (1969)
Volume
99
Issue
2
Publish Date
1992
Start Page
282
End Page
291

Generation of narrowband inversion with broadband laser pulses

We show experimentally, here for Na vapor, and theoretically that picosecond frequency-swept laser pulses create in multilevel systems an inversion profile that is far narrower than the pulse spectrum. This selectivity persists even when the Rabi frequency is substantially larger than the spacing between pumped and suppressed transitions. © 1992 The American Physical Society.

Authors
Melinger, JS; Gandhi, SR; Hariharan, A; Tull, JX; Warren, WS
MLA Citation
Melinger, JS, Gandhi, SR, Hariharan, A, Tull, JX, and Warren, WS. "Generation of narrowband inversion with broadband laser pulses." Physical Review Letters 68.13 (1992): 2000-2003.
Source
scival
Published In
Physical Review Letters
Volume
68
Issue
13
Publish Date
1992
Start Page
2000
End Page
2003
DOI
10.1103/PhysRevLett.68.2000

Population transfer by stimulated Raman scattering with delayed pulses using spectrally broad light

The feasability of selective and complete population transfer between atomic or molecular levels by stimulated Raman scattering with delayed pulses involving spectrally broad light with characteristics typical for pulsed lasers is investigated. In extension of previous work, the effect on the transfer efficiency of phase fluctuations and of the detuning ΔR of the laser frequencies from the two-photon resonance is analyzed. The minimum pulse energy Pmin required to achieve a transfer efficiency of nearly unity is derived analytically, with some restrictions imposed on the type of phase fluctuations. Pmin increases approximately proportional to the square of the bandwidth of the laser radiation and to the square of ΔR. The conclusions are confirmed by the results of extensive numerical calculations. These studies also reveal a high sensitivity of the transfer efficiency to the autocorrelation of the fluctuating light. © 1992 American Institute of Physics.

Authors
Kuhn, A; Coulston, GW; He, GZ; Schiemann, S; Bergmann, K; Warren, WS
MLA Citation
Kuhn, A, Coulston, GW, He, GZ, Schiemann, S, Bergmann, K, and Warren, WS. "Population transfer by stimulated Raman scattering with delayed pulses using spectrally broad light." The Journal of Chemical Physics 96.6 (1992): 4215-4223.
Source
scival
Published In
Journal of Chemical Physics
Volume
96
Issue
6
Publish Date
1992
Start Page
4215
End Page
4223

Reply to the comment on: Is multiple quantum nuclear magnetic resonance of water real? [5]

Authors
Warren, WS; He, Q; McCoy, M; Spano, FC
MLA Citation
Warren, WS, He, Q, McCoy, M, and Spano, FC. "Reply to the comment on: Is multiple quantum nuclear magnetic resonance of water real? [5]." The Journal of Chemical Physics 96.2 (1992): 1659-1661.
Source
scival
Published In
Journal of Chemical Physics
Volume
96
Issue
2
Publish Date
1992
Start Page
1659
End Page
1661

Adiabatic population inversion in I2 vapor with picosecond laser pulses

Authors
Melinger, JS; Hariharan, A; Gandhi, SR; Warren, WS
MLA Citation
Melinger, JS, Hariharan, A, Gandhi, SR, and Warren, WS. "Adiabatic population inversion in I2 vapor with picosecond laser pulses." The Journal of Chemical Physics 95.3 (1991): 2210-2213.
Source
scival
Published In
Journal of Chemical Physics
Volume
95
Issue
3
Publish Date
1991
Start Page
2210
End Page
2213

Optimal design of external fields for controlling molecular motion: application to rotation

A general discussion of quantum controllability leads to the specific focus of this work, namely the use of tailored radiation to excite rotational states, either specific |JM〉 states or superposition states which correspond to a high degree of molecular orientation. It is shown that starting from the |00> state it is in principle possible to produce any eigenstate or superposition state given a long enough pulse and specific examples are presented. Highly ordered states, which are useful in a variety of spectroscopic applications, can be prepared by realistic tailored microwave fields. © 1990.

Authors
Judson, RS; Lehmann, KK; Rabitz, H; Warren, WS
MLA Citation
Judson, RS, Lehmann, KK, Rabitz, H, and Warren, WS. "Optimal design of external fields for controlling molecular motion: application to rotation." Journal of Molecular Structure 223.C (1990): 425-456.
Source
scival
Published In
Journal of Molecular Structure
Volume
223
Issue
C
Publish Date
1990
Start Page
425
End Page
456
DOI
10.1016/0022-2860(90)80485-3

Three-quantum nuclear magnetic resonance spectroscopy of liquid water: Intermolecular multiple-quantum coherence generated by spin-cavity coupling

Authors
McCoy, MA; Warren, WS
MLA Citation
McCoy, MA, and Warren, WS. "Three-quantum nuclear magnetic resonance spectroscopy of liquid water: Intermolecular multiple-quantum coherence generated by spin-cavity coupling." The Journal of Chemical Physics 93.1 (1990): 858-860.
Source
scival
Published In
Journal of Chemical Physics
Volume
93
Issue
1
Publish Date
1990
Start Page
858
End Page
860

Investigation of momentum relaxation and time-dependent conductance in radiation-damaged GaAs

We report experimental characterization of a transient capacitative electrical effect in a GaAs photoconductive switch due to initial momentum relaxation of the carriers within the photoexcited plasma. The carrier-momentum-dampening rate (d) of approximately 1 ps is characterized by optical square-pulse excitation in a radiation-damaged GaAs substrate, which produces asymmetries in the electrical impulse response of the photoconductor. Defect densities in the radiation-damaged samples are measured with use of medium-energy Rutherford backscattering and correlated with the electrical characteristics. Simulations of the electron transport and electrical response under our experimental conditions agree favorably with the observed electrical characteristics of the photoconductor. We discuss the effect of plasma dampening on electrical-switching characteristics and the site-defect capture process. © 1990 The American Physical Society.

Authors
Haner, M; Warren, WS
MLA Citation
Haner, M, and Warren, WS. "Investigation of momentum relaxation and time-dependent conductance in radiation-damaged GaAs." Physical Review B 41.9 (1990): 5792-5798.
Source
scival
Published In
Physical Review B - Condensed Matter and Materials Physics
Volume
41
Issue
9
Publish Date
1990
Start Page
5792
End Page
5798
DOI
10.1103/PhysRevB.41.5792

Photon echo decays in optically dense media

In this paper we investigate the influence of optical density or superradiance on the photon echo decay using the coupled Maxwell-Bloch equations. Our theory applies to optically thick but dilute media, where the transition dipole-dipole interaction between nearby chromophores is negligible, but the far-field interaction is not. Corrections to the (normalized) echo decay in the optically thin limit, IeN(tπ) = exp [-4tπ/T2] (tπ and T2 are the interpulse separation times and the coherence relaxation times, respectively), are found by expanding the polarization, excited state population and pulse electric fields in powers of ζ = αz, where α is the inverse Beer's absorption length, and z is the coordinate along the pulse propagation axis. Numerical solutions for optically thick samples are also presented, and when ζ≫ 1 the normalized echo intensity is found to obey the simple analytic form: IeN(tπ) = 2 exp [- t π/T1] - 1, when tπ/T1<1n 2 and IeN (tπ) = 0 for longer times. (T 1 is the population relaxation time.) In this limit the echo decay is independent of the coherence relaxation time T2, illustrating the profound effect intermolecular coupling may have on any nonlinear optical measurement. We show that at low temperatures, when T2 = 2T 1, the echo decay rate increases as the optical density increases. However, for higher temperatures, when T2 is sufficiently shorter than 2T1, the opposite behavior results, that is, the echo decay rate decreases as the optical density increases. © 1990 American Institute of Physics.

Authors
Spano, FC; Warren, WS
MLA Citation
Spano, FC, and Warren, WS. "Photon echo decays in optically dense media." The Journal of Chemical Physics 93.3 (1990): 1546-1556.
Source
scival
Published In
Journal of Chemical Physics
Volume
93
Issue
3
Publish Date
1990
Start Page
1546
End Page
1556

Spectroscopic applications of programmable subpicosecond resolution laser pulse shaping

A method has been developed for producing voltage-programmable, arbitrarily shaped laser pulses with approximately 100-fs resolution and >107-W peak power. Rectangular 600-1500-fs pulses have been used to probe hot carrier relaxation by photoconductive sampling, and phase- and amplitude-modulated laser pulses have been used to create complex solitons in optical fibers. Other applications that illustrate the use of shaped laser pulses in atomic and molecular spectroscopy are briefly described, as is the use of optical analogs of spin-locking experiments to turn off intramolecular vibrational redistribution.

Authors
Warren, WS
MLA Citation
Warren, WS. "Spectroscopic applications of programmable subpicosecond resolution laser pulse shaping." (1989): 82-84.
Source
scival
Publish Date
1989
Start Page
82
End Page
84

Energy redistribution from high vibrational levels populated by stimulated emission pumping

Laser pulses with finely controlled amplitude envelopes can selectively invert a portion of a Doppler broadened line, but the extent of inversion varies as the Rabi frequency of the transition changes. Modulation of the phase in addition to the amplitude can compensate for Rabi frequency variations, and pulses can be designed to invert a transition completely over a chosen well-defined frequency range. Using such a pulse, ground-state molecules within a selected range of velocities can be put into an electronically excited state and with a second pulse subsequently transferred to a high vibrational level of the ground electronic state. Excitation of a narrow and well-defined portion of a Doppler profile allows not only vibrational and rotational thermalization of the molecules to be followed but also subtle changes in translational energy of the state. Collisional cross sections of ground-state molecules with many vibrational quanta can be directly compared with cross sections obtained from electronically excited molecules to reveal electronic state contributions to collisional dynamics.

Authors
Wooldridge, PJ; Bates, JL; Lin, CP; Warren, WS
MLA Citation
Wooldridge, PJ, Bates, JL, Lin, CP, and Warren, WS. "Energy redistribution from high vibrational levels populated by stimulated emission pumping." (1989): 44--.
Source
scival
Publish Date
1989
Start Page
44-

NMR dipole-dipole refocusing with shaped pulses

Authors
Lee, CJ; Murali, N; Warren, WS
MLA Citation
Lee, CJ, Murali, N, and Warren, WS. "NMR dipole-dipole refocusing with shaped pulses." Journal of Magnetic Resonance (1969) 84.3 (1989): 643-647.
Source
scival
Published In
Journal of Magnetic Resonance (1969)
Volume
84
Issue
3
Publish Date
1989
Start Page
643
End Page
647

Symmetry properties of coupled spin systems under arbitrarily shaped radiofrequency pulse fields

Authors
Lee, CJ; Warren, WS
MLA Citation
Lee, CJ, and Warren, WS. "Symmetry properties of coupled spin systems under arbitrarily shaped radiofrequency pulse fields." Journal of Magnetic Resonance (1969) 82.1 (1989): 185-192.
Source
scival
Published In
Journal of Magnetic Resonance (1969)
Volume
82
Issue
1
Publish Date
1989
Start Page
185
End Page
192
DOI
10.1016/0022-2364(89)90181-9

Understanding dephasing in mixed molecular crystals. II. Semiclassical dephasing and superradiance for hundreds of coupled absorbers

We numerically investigate optical dephasing from as many as 500 interacting two-level absorbers by making the semiclassical approximation on the radiation-matter interaction which includes retarded dipole-dipole coupling and superradiant coupling. We calculate the superradiant decay rate following single pulse optical excitation, the photon echo decay and the fluorescence. By carrying out an expansion to the second order in time we demonstrate a fundamental difference between the homogeneous free-induction decay and photon echo decay which is due to radiation damping. We show that an echo sequence is capable of reversing superradiant damping in some cases. Specific computations for pentacene doped mixed molecular crystals, where "domains" of resonant impurities are likely to exist, are presented and compared with experimental results. © 1989 American Institute of Physics.

Authors
Spano, FC; Warren, WS
MLA Citation
Spano, FC, and Warren, WS. "Understanding dephasing in mixed molecular crystals. II. Semiclassical dephasing and superradiance for hundreds of coupled absorbers." The Journal of Chemical Physics 90.11 (1989): 6034-6046.
Source
scival
Published In
Journal of Chemical Physics
Volume
90
Issue
11
Publish Date
1989
Start Page
6034
End Page
6046

Spectroscopic applications of programmable subpicosecond resolution laser pulse shaping

A method has been developed for producing voltage-programmable, arbitrarily shaped laser pulses with ~100-fs resolution and >107-W peak power. Rectangular 600-1500-fs pulses have been used to probe hot carrier relaxation by photoconductive sampling, and phase- and amplitude-modulated laser pulses have been used to create complex solitons in optical fibers. Other applications that illustrate the use of shaped laser pulses in atomic and molecular spectroscopy are briefly described, as is the use of optical analogs of spin-locking experiments to turn off intramolecular vibrational redistribution.

Authors
Warren, WS
MLA Citation
Warren, WS. "Spectroscopic applications of programmable subpicosecond resolution laser pulse shaping." CONFERENCE ON LASERS AND ELECTRO-0PTICS (1989): 154--.
Source
scival
Published In
CONFERENCE ON LASERS AND ELECTRO-0PTICS
Publish Date
1989
Start Page
154-

Dynamics of radiation damping in nuclear magnetic resonance

The time evolution of spins-1/2 subject to radiation damping, which is commonly encountered for solvent peaks at high field, is examined in detail. The well-known analytic results for rectangular pulses on undamped spin-1/2 systems are extended to the radiation damped case, and reveal surprisingly complex dynamics. Explanations in terms of Bloch vectors are also presented, and composite pulse sequences which would also be insensitive to radiation damping are proposed. In addition, gradient optimization programs were developed to find shaped π and π/2 pulses insensitive to radiation damping. The optimized pulses compensate for radiation damping effects even when the characteristic damping time is shorter than the pulse length. © 1989 American Institute of Physics.

Authors
Warren, WS; Hammes, SL; Bates, JL
MLA Citation
Warren, WS, Hammes, SL, and Bates, JL. "Dynamics of radiation damping in nuclear magnetic resonance." The Journal of Chemical Physics 91.10 (1989): 5895-5904.
Source
scival
Published In
Journal of Chemical Physics
Volume
91
Issue
10
Publish Date
1989
Start Page
5895
End Page
5904

Selective excitation without phase distortion using self-refocused amplitude- and amplitude/phase-modulated pulses

Authors
Loaiza, F; McCoy, MA; Hammes, SL; Warren, WS
MLA Citation
Loaiza, F, McCoy, MA, Hammes, SL, and Warren, WS. "Selective excitation without phase distortion using self-refocused amplitude- and amplitude/phase-modulated pulses." Journal of Magnetic Resonance (1969) 77.1 (1988): 175-181.
Source
scival
Published In
Journal of Magnetic Resonance (1969)
Volume
77
Issue
1
Publish Date
1988
Start Page
175
End Page
181

Self-refocused solvent suppression with shaped pulses

Authors
McCoy, MA; Loaiza, F; Valentine, K; Warren, WS
MLA Citation
McCoy, MA, Loaiza, F, Valentine, K, and Warren, WS. "Self-refocused solvent suppression with shaped pulses." Journal of Magnetic Resonance (1969) 80.1 (1988): 155-161.
Source
scival
Published In
Journal of Magnetic Resonance (1969)
Volume
80
Issue
1
Publish Date
1988
Start Page
155
End Page
161

Synthesis of crafted optical pulses by time domain modulation in a fiber-grating compressor

We report a method for direct generation of voltage programmable, arbitrarily shaped laser pulses of subpicosecond duration and roughly 100 fs resolution. A waveguide intensity modulator was fabricated and incorporated into a fiber-grating pulse compressor to shape temporally the chirped pulse before compression. Optical pulses with sin(x)/x and square envelopes are synthesized to demonstrate the technique.

Authors
Haner, M; Warren, WS
MLA Citation
Haner, M, and Warren, WS. "Synthesis of crafted optical pulses by time domain modulation in a fiber-grating compressor." Applied Physics Letters 52.18 (1988): 1458-1460.
Source
scival
Published In
Applied Physics Letters
Volume
52
Issue
18
Publish Date
1988
Start Page
1458
End Page
1460
DOI
10.1063/1.99097

Excitation performance in inhomogeneously broadened systems

The problem of predicting through numerical simulation the performance of pulse sequences applied to inhomogeneously broadened spin systems is examined. Numerical or analytical calculations of the dependence of magnetization on frequency do not lead immediately to the actual form of the spectrum in the inhomogeneously broadened case. To predict the spectrum it is usually necessary to proceed through the time domain and to take into account the fact that the experimental data of negative times are usually not accessible. These results are particularly relevant to the optimization of pulse sequences for multislice imaging at zero gap. Experimental results from high-resolution NMR and magnetic resonance imaging verify these ideas. © 1988.

Authors
Loaiza, F; McCoy, MA; Levitt, MH; Silver, MS; Warren, WS
MLA Citation
Loaiza, F, McCoy, MA, Levitt, MH, Silver, MS, and Warren, WS. "Excitation performance in inhomogeneously broadened systems." Journal of Magnetic Resonance (1969) 76.3 (1988): 504-527.
Source
scival
Published In
Journal of Magnetic Resonance (1969)
Volume
76
Issue
3
Publish Date
1988
Start Page
504
End Page
527

Understanding of phase modulation in two-level systems through inverse scattering

Analytical and numerical calculations describe the effects of shaped radiation pulses on two-level systems in terms of quantum-mechanical scattering. Previous results obtained in the reduced case of amplitude modulation are extended to the general case of simultaneous amplitude and phase modulation. We show that an infinite family of phase- and amplitude-modulated pulses all generate rectangular inversion profiles. Experimental measurements also verify the theoretical analysis. © 1988 The American Physical Society.

Authors
Hasenfeld, A; Hammes, SL; Warren, WS
MLA Citation
Hasenfeld, A, Hammes, SL, and Warren, WS. "Understanding of phase modulation in two-level systems through inverse scattering." Physical Review A 38.5 (1988): 2678-2681.
Source
scival
Published In
Physical Review A - Atomic, Molecular, and Optical Physics
Volume
38
Issue
5
Publish Date
1988
Start Page
2678
End Page
2681
DOI
10.1103/PhysRevA.38.2678

Neonatal Campylobacter meningitis.

Authors
Mahajan, AB; Warren, WS; Paszek, MJ; Olarte, F; Jr, AC
MLA Citation
Mahajan, AB, Warren, WS, Paszek, MJ, Olarte, F, and Jr, AC. "Neonatal Campylobacter meningitis." Pennsylvania Medicine 91.1 (1988): 58-61.
Source
scival
Published In
Pennsylvania Medicine
Volume
91
Issue
1
Publish Date
1988
Start Page
58
End Page
61

Effects of pulse shaping in laser spectroscopy and nuclear magnetic resonance.

Pulsed excitation fields are routinely used in most laser and nuclear magnetic resonance (NMR) experiments. In the NMR case, constant amplitude (rectangular) pulses have traditionally been used; in laser spectroscopy the exact pulse shape is often unknown or changes from shot to shot. This article is an overview of the effects of radio-frequency and laser pulse shapes and the instrumental requirements for pulse shaping. NMR applications to selective excitation, solvent suppression, elimination of phase roll, and reduced power dissipation are discussed, as are optical applications to soliton generation, velocity selective excitation, and quantitative population transfer.

Authors
Warren, WS
MLA Citation
Warren, WS. "Effects of pulse shaping in laser spectroscopy and nuclear magnetic resonance." Science 242.4880 (1988): 878-884.
PMID
3055299
Source
scival
Published In
Science
Volume
242
Issue
4880
Publish Date
1988
Start Page
878
End Page
884

FRODO pulse sequences: A new means of eliminating motion, flow and wraparound artifacts

Magnetic resonance images of the spine, chest, abdomen, and pelvis are commonly degraded by ghost artifacts. The authors have developed a new technique named FRODO (Flow and Respiratory artifact Obliteration with Directed Orthogonal pulses) to suppress these artifacts. Signal from tissues responsible for the artifacts is eliminated by use of radio frequency pulses specifically optimized for high selectivity to saturate proton magnetization over one or more independently defined slabs (large rectangular volumes) of tissue. Ghost artifacts from pulsatile flow in the heart and blood vessels, as well as from respiratory motion and swallowing, are suppressed. Additional applications of this technique include elimination of intraluminal signal in blood vessels and suppression of wraparound artifact along the phase-encoding axis. Preliminary clinical experience suggests that the FRODO technique, in conjunction with other flow compensation methods, may provide a definitive solution to the problem of motion in spine imaging. FRODO pulse sequences may also prove useful for imaging of blood vessels, heart, abdomen, and other areas where motion, flow, or wraparound artifacts limit image quality.

Authors
Edelman, RR; Atkinson, DJ; Silver, MS; Loaiza, F; Warren, WS
MLA Citation
Edelman, RR, Atkinson, DJ, Silver, MS, Loaiza, F, and Warren, WS. "FRODO pulse sequences: A new means of eliminating motion, flow and wraparound artifacts." Radiology 166.1 I (1988): 231-236.
PMID
3336685
Source
scival
Published In
Radiology
Volume
166
Issue
1 I
Publish Date
1988
Start Page
231
End Page
236

Understanding dephasing in mixed molecular crystals. I. Photon echoes from dimers revisited

We show that a fundamental assumption used in analyzing photon echo decays from interacting molecules - the assumption that the "pure" dephasing rate can be obtained by subtracting one half of the fluorescence decay rate (2T1)-1 from the photon echo decay rate-is generally inconsistent with a fully quantum mechanical treatment. The density matrix evolution for a system of noninteracting dimers is calculated using the retarded electromagnetic coupling between two oscillating dipoles. We are able to properly include the effects of spontaneous emission and Dicke superradiance on the echo decay. © 1988 American Institute of Physics.

Authors
Spano, FC; Warren, WS
MLA Citation
Spano, FC, and Warren, WS. "Understanding dephasing in mixed molecular crystals. I. Photon echoes from dimers revisited." The Journal of Chemical Physics 89.9 (1988): 5492-5497.
Source
scival
Published In
Journal of Chemical Physics
Volume
89
Issue
9
Publish Date
1988
Start Page
5492
End Page
5497

Preparation of constant-bandwidth total inversion, independent of optical density, with phase-modulated laser pulses

We show that pulses of electromagnetic radiation with a hyperbolic-secant envelope and a hyperbolic-tangent frequency sweep are capable of exciting an inversion line shape in a collection of two-level absorbers that is highly insensitive to optical density. This is not true of the hyperbolic-secant pulse (with no frequency modulation) which undergoes significant reshaping as it propagates. The analysis is based on numerical solutions of the coupled Maxwell-Bloch equations in both the plane-wave and paraxial approximations. We also show an additional insensitivity of the inversion profile to finite relaxation times (T2) that approach the pulse width. © 1988 The American Physical Society.

Authors
Spano, FC; Warren, WS
MLA Citation
Spano, FC, and Warren, WS. "Preparation of constant-bandwidth total inversion, independent of optical density, with phase-modulated laser pulses." Physical Review A 37.3 (1988): 1013-1016.
Source
scival
Published In
Physical Review A - Atomic, Molecular, and Optical Physics
Volume
37
Issue
3
Publish Date
1988
Start Page
1013
End Page
1016
DOI
10.1103/PhysRevA.37.1013

Spectroscopic demonstration of picosecond, phase-shifted laser multiple-pulse sequences

We show that the concept of phase-shifted laser pulse trains is meaningful only for purely amplitude-modulated pulses, and probably cannot be generalized to use the output of a normal pulsed laser. We demonstrate a laser system which gives picosecond pulse lengths, picosecond or nanosecond interpulse delays, and complete phase control. This makes most molecular transitions amenable to the coherent techniques previously restricted to nuclear magnetic resonance. Fluorescence suppression by π phase shifts is demonstrated for the first time with picosecond pulses and long delays. © 1987.

Authors
Spzno, F; Haner, M; Warren, WS
MLA Citation
Spzno, F, Haner, M, and Warren, WS. "Spectroscopic demonstration of picosecond, phase-shifted laser multiple-pulse sequences." Chemical Physics Letters 135.1-2 (1987): 97-102.
Source
scival
Published In
Chemical Physics Letters
Volume
135
Issue
1-2
Publish Date
1987
Start Page
97
End Page
102
DOI
10.1016/0009-2614(87)87224-X

Erratum: Implementation of a phase and amplitude modulated π pulse for coherent optical spectroscopy (Journal of Chemical Physics (1987) 86 (3750))

Authors
Lin, CP; Bates, J; Mayer, JT; Warren, WS
MLA Citation
Lin, CP, Bates, J, Mayer, JT, and Warren, WS. "Erratum: Implementation of a phase and amplitude modulated π pulse for coherent optical spectroscopy (Journal of Chemical Physics (1987) 86 (3750))." The Journal of Chemical Physics 87.7 (1987): 4241--.
Source
scival
Published In
Journal of Chemical Physics
Volume
87
Issue
7
Publish Date
1987
Start Page
4241-

Pulse shaping to improve performance of NMR multiple-pulse sequences: 2-D solvent-suppressed cosy of vitamin B1 in water

Grafted "narrow reject" pulse shapes, whicch were shown previously to be capable of uniformly exciting a wide range of resonance frequencies with a sharp null directly on resonance for solvent suppression, are combined to generate multiple-pulse sequences. In particular, we show that two-dimensional solvent-suppressed spectra can be obtained with such pulses. This is the first application of pulse Grafting to high-resolution, multiple-pulse NMR spectroscopy. © 1987.

Authors
McCoy, M; Warren, WS
MLA Citation
McCoy, M, and Warren, WS. "Pulse shaping to improve performance of NMR multiple-pulse sequences: 2-D solvent-suppressed cosy of vitamin B1 in water." Chemical Physics Letters 133.2 (1987): 165-170.
Source
scival
Published In
Chemical Physics Letters
Volume
133
Issue
2
Publish Date
1987
Start Page
165
End Page
170
DOI
10.1016/0009-2614(87)87043-4

Crafted pulses for imaging and in vivo NMR spectroscopy

Authors
Loaiza, F; McCoy, MA; Warren, WS; Silver, MS; Egloff, H
MLA Citation
Loaiza, F, McCoy, MA, Warren, WS, Silver, MS, and Egloff, H. "Crafted pulses for imaging and in vivo NMR spectroscopy." Annals of the New York Academy of Sciences 508 (1987): 483-487.
Source
scival
Published In
Annals of the New York Academy of Sciences
Volume
508
Publish Date
1987
Start Page
483
End Page
487

Student strategies in a junior-level procedureless laboratory

Authors
Warren, WS; Pickering, M
MLA Citation
Warren, WS, and Pickering, M. "Student strategies in a junior-level procedureless laboratory." Journal of Chemical Education 64.1 (1987): 68-69.
Source
scival
Published In
Journal of Chemical Education
Volume
64
Issue
1
Publish Date
1987
Start Page
68
End Page
69

EFFECTS OF PULSE SHAPING IN LASER SPECTROSCOPY.

We have shown theoretically and experimentally that specially shaped laser pulses can give enhanced excitation selectivity, compensate for experimental complications such as inhomogeneities and pulse amplitude jitter, and cleanly pump forbidden transitions. A new approach to generating picosecond pulses, which does not require modelocking, permits software controlled, arbitrarily shaped (phase and amplitude modulated) pulses with roughly 1 ps resolution.

Authors
Warren, WS
MLA Citation
Warren, WS. "EFFECTS OF PULSE SHAPING IN LASER SPECTROSCOPY." Proceedings of SPIE - The International Society for Optical Engineering 742 (1987): 42-46.
Source
scival
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
742
Publish Date
1987
Start Page
42
End Page
46

Implementation of a phase and amplitude modulated π pulse for coherent optical spectroscopy

Authors
Lin, CP; Bates, J; Mayer, JT; Warren, WS
MLA Citation
Lin, CP, Bates, J, Mayer, JT, and Warren, WS. "Implementation of a phase and amplitude modulated π pulse for coherent optical spectroscopy." The Journal of Chemical Physics 86.6 (1987): 3750-3751.
Source
scival
Published In
Journal of Chemical Physics
Volume
86
Issue
6
Publish Date
1987
Start Page
3750
End Page
3751

Crafted pulses and pulse sequences for MR imaging

Authors
Loaiza, F; Lim, K-T; Warren, WS
MLA Citation
Loaiza, F, Lim, K-T, and Warren, WS. "Crafted pulses and pulse sequences for MR imaging." Health Care Instrumentation 1.6 (1986): 188-194.
Source
scival
Published In
Health Care Instrumentation
Volume
1
Issue
6
Publish Date
1986
Start Page
188
End Page
194

THEORETICAL ANALYSIS OF INJECTION-LOCKED DYE LASERS: AN APPLICATION TO THE GENERATION OF OPTICAL PULSE SEQUENCES WITH PHASE CONTROL.

A theoretical model based on the laser rate equations is used to describe injection locking in pulsed dye lasers. It is shown that, in general, the frequency of the injection locked pulse is not equal to the frequency of the cw light-an unexpected result since the two are related through stimulated emission. We discuss how to accommodate this feature in the design of a specialized delay line used to create optical pulse sequences with variable phase shifts between the pulses.

Authors
Spano, F; Warren, WS
MLA Citation
Spano, F, and Warren, WS. "THEORETICAL ANALYSIS OF INJECTION-LOCKED DYE LASERS: AN APPLICATION TO THE GENERATION OF OPTICAL PULSE SEQUENCES WITH PHASE CONTROL." Proceedings of SPIE - The International Society for Optical Engineering 620 (1986): 52-56.
Source
scival
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
620
Publish Date
1986
Start Page
52
End Page
56

Implementation of simple crafted 90 or 180° pulse shapes in fourier transform NMR spectroscopy

Authors
McCoy, MA; Warren, WS
MLA Citation
McCoy, MA, and Warren, WS. "Implementation of simple crafted 90 or 180° pulse shapes in fourier transform NMR spectroscopy." Journal of Magnetic Resonance (1969) 65.1 (1985): 178-182.
Source
scival
Published In
Journal of Magnetic Resonance (1969)
Volume
65
Issue
1
Publish Date
1985
Start Page
178
End Page
182

COHERENT AND INCOHERENT DUAL-FREQUENCY OPTICAL SPECTROSCOPY: APPLICATIONS TO GAS PHASE COLLISIONAL DYNAMICS.

Summary form only given. The authors present work with coherent and incoherent dual-frequency experiments designed to measure detailed microscopic collisional dynamics in molecular gases. In the incoherent version, a laser pulse sequence consisting of two 180 degree pulses (each 100 ns long) is applied. Each pulse has a bandwidth such that only a narrow range of velocities in the Doppler profile is excited. As both pulses are 180 degree and not phase specific, this incoherent experiment measures population transfer between velocity ranges. In the coherent version both pulses are 90 degree and phase specific, so the experiment measures collisional effects on phase memory.

Authors
Banash, MA; Warren, WS
MLA Citation
Banash, MA, and Warren, WS. "COHERENT AND INCOHERENT DUAL-FREQUENCY OPTICAL SPECTROSCOPY: APPLICATIONS TO GAS PHASE COLLISIONAL DYNAMICS." (1985): 132-133.
Source
scival
Publish Date
1985
Start Page
132
End Page
133

Crafted pulses for the uniform suppression of a region in a coherent spectrum

We have theoretically derived and experimentally demonstrated "narrow reject" pulses which give a uniform 2 excitation off resonance, and zero excitation in a sharp hole directly on resonance. They are also insensitive to relaxation effects. This shape is symmetric and has only amplitude modulation, and so it can be implemented on most commercial NMR spectrometers or with laser modulators. It can replace conventional broadband 2 pulses in most NMR or laser pulse sequences, in order to give solvent suppression or measure spectral diffusion. © 1985 The American Physical Society.

Authors
Gutow, JH; McCoy, M; Spano, F; Warren, WS
MLA Citation
Gutow, JH, McCoy, M, Spano, F, and Warren, WS. "Crafted pulses for the uniform suppression of a region in a coherent spectrum." Physical Review Letters 55.10 (1985): 1090-1093.
Source
scival
Published In
Physical Review Letters
Volume
55
Issue
10
Publish Date
1985
Start Page
1090
End Page
1093
DOI
10.1103/PhysRevLett.55.1090

Luminescence as a probe of coherence: Applications to collisional dynamics and phase coherent spectroscopy

Measurement of luminescence rather than polarization in coherent optical experiments allows more molecular information to be extracted. In this paper we discuss the advantages of this technique, such as frequency selectivity and time resolution, and applications to gas phase collisional dynamics. © 1984.

Authors
Banash, MA; Gutow, J; Warren, WS
MLA Citation
Banash, MA, Gutow, J, and Warren, WS. "Luminescence as a probe of coherence: Applications to collisional dynamics and phase coherent spectroscopy." Journal of Luminescence 31-32.PART 2 (1984): 855-857.
Source
scival
Published In
Journal of Luminescence
Volume
31-32
Issue
PART 2
Publish Date
1984
Start Page
855
End Page
857

Computer simulations of multiple-quantum NMR experiments. I. Nonselective excitation

The multiple-quantum (MQ evolution of anisotropic spin systems with four to eight coupled protons is analyzed using a computer for the basic three-pulse sequence. MQ intensities are first investigated as a function of preparation time. The concept of time-independent intensities is then introduced, and an algorithm for efficient computation of these quantities is described. A correlation between the distribution of dipolar coupling values and the intensity of high-quantum lines is discussed; in many cases, these intensities are predicted to be considerably larger than a simple statistical argument would suggest. The effect of varying the preparation and detection times independently is analyzed as a random walk problem. © 1984.

Authors
Murdoch, JB; Warren, WS; Weitekamp, DP; Pines, A
MLA Citation
Murdoch, JB, Warren, WS, Weitekamp, DP, and Pines, A. "Computer simulations of multiple-quantum NMR experiments. I. Nonselective excitation." Journal of Magnetic Resonance (1969) 60.2 (1984): 205-235.
Source
scival
Published In
Journal of Magnetic Resonance (1969)
Volume
60
Issue
2
Publish Date
1984
Start Page
205
End Page
235

Computer simulations of multiple-quantum NMR experiments. II. Selective excitation

The effects of selective multiple-quantum pulse sequences have previously been analyzed by coherent averaging theory. However, convergence of the Magnus expansion used for those calculations is questionable in the experimentally important region of long cycle times. Exact density matrix evolutions are calculated here to show when the coherent averaging calculations will be reliable. In addition, simple selective sequences which cannot be treated by coherent averaging theory are also analyzed. © 1984.

Authors
Warren, WS; Murdoch, JB; Pines, A
MLA Citation
Warren, WS, Murdoch, JB, and Pines, A. "Computer simulations of multiple-quantum NMR experiments. II. Selective excitation." Journal of Magnetic Resonance (1969) 60.2 (1984): 236-256.
Source
scival
Published In
Journal of Magnetic Resonance (1969)
Volume
60
Issue
2
Publish Date
1984
Start Page
236
End Page
256

PHASE COHERENT LASER MUTIPLE-PULSE SPECTROSCOPY.

Authors
Banash, M; Loiza, F; Spano, F; Warren, WS
MLA Citation
Banash, M, Loiza, F, Spano, F, and Warren, WS. "PHASE COHERENT LASER MUTIPLE-PULSE SPECTROSCOPY." (1984): 131--.
Source
scival
Publish Date
1984
Start Page
131-

Effects of arbitrary laser or NMR pulse shapes on population inversion and coherence

We present a new perturbation expansion for calculating the effects of arbitrary pulse shapes in two-level systems, even when the effects are grossly nonlinear. The first two terms have simple physical interpretations. This expansion converges rapidly for all values of resonance offset with simple shapes, and for any pulse shape far from resonance. We generate very simple, symmetric, single phase pulse shapes which produce uniform inversion or polarization and which can be combined into multiple pulse sequences. We also show that pulse shape modification is superior to construction of composite pulse sequences, since such sequences must become erratic far from resonance. © 1984 American Institute of Physics.

Authors
Warren, WS
MLA Citation
Warren, WS. "Effects of arbitrary laser or NMR pulse shapes on population inversion and coherence." The Journal of Chemical Physics 81.12 (1984): 5437-5448.
Source
scival
Published In
Journal of Chemical Physics
Volume
81
Issue
12
Publish Date
1984
Start Page
5437
End Page
5448

Intervalence excitations of a mixed-valence salt: NMR and optical absorption in molten InCl2

We report115 In nuclear relaxation rates for molten InCl2 and visible-near-infrared absorption spectra for molten InCl2 and In2Cl3. A weak band at 2.1 eV in InCl2 is attributed to the intervalence transfer excitation In+ →- In3+. The intensity of the intervalence band is correlated with the lifetime of the excited, magnetic ion In2+ measured by NMR. © 1983.

Authors
Jr, WW; Schönherr, G; Hensel, F
MLA Citation
Jr, WW, Schönherr, G, and Hensel, F. "Intervalence excitations of a mixed-valence salt: NMR and optical absorption in molten InCl2." Chemical Physics Letters 96.4 (1983): 505-508.
Source
scival
Published In
Chemical Physics Letters
Volume
96
Issue
4
Publish Date
1983
Start Page
505
End Page
508

Optical multiple pulse sequences for multiphoton selective excitation and enhancement of forbidden transitions

In this paper we present novel and simple pulse sequences for enhancing the intensity of forbidden or highly nonresonant optical transitions. These sequences provide a straightforward approach to circumventing the most serious limitation of optical coherent transient spectroscopy: Available laser intensities are often insufficient to excite a significant fraction of the ground state population into desired excited states, either because of large inhomogeneous broadening or, in the case of multiphoton absorption, large anharmonicities. Optical phase modulation (which can be produced by an acousto-optic modulator) or amplitude modulation (which can be produced by an interferometer) with carefully chosen pulse flip angles and delays can effectively remove even very large energy mismatches, thus permitting essentially complete population inversions arbitrarily far from resonance. Coherent averaging theory and computer calculations are used to derive particularly valuable sequences. Pumping enhancement of 103-10 5 (depending on individual molecular parameters) for these modulated pulse sequences are predicted. Specific applications to multiphoton pumping of local vibrational modes are discussed. © 1983 American institute of Physics.

Authors
Warren, WS; Zewail, AH
MLA Citation
Warren, WS, and Zewail, AH. "Optical multiple pulse sequences for multiphoton selective excitation and enhancement of forbidden transitions." The Journal of Chemical Physics 78.6 (1983): 3583-3592.
Source
scival
Published In
Journal of Chemical Physics
Volume
78
Issue
6
Publish Date
1983
Start Page
3583
End Page
3592

Multiple phase-coherent laser pulses in optical spectroscopy. II. Applications to multilevel systems

The effects of intense laser pulse trains in coupled multilevel systems (such as pure or mixed molecular crystals) are analyzed by calculating exact density matrix evolutions. It is shown that two-level approximations are inadequate. The contributions of exchange couplings, inhomogeneous broadening, permanent multipole interactions and transition multipole interactions to absorption and photon echo line shapes are calculated. The absorption line shape of 1,4-dibromonaphthalene (DBN) is shown to be predominantly an isotopic substitution effect, as our Monte Carlo results give quantitative agreement with experiment for this model. Average t-matrix approximations to the Green's function, which have been used to propose a different mechanism for the DBN line shape are shown to be qualitatively inadequate. Dipole-dipole interactions are shown to be an important photon echo decay mechanism in mixed crystals, with the relative importance of permanent and transition multipole interactions dependent on the resonance frequency distribution. Multiple pulse trains, including multiple pulse echoes and optical multiple-quantum sequences, are shown to be capable of distinguishing different types of interactions in the molecular Hamiltonian and reducing optical density effects. Specific pulse sequences are proposed and their effects are calculated. © 1983 American Institute of Physics.

Authors
Warren, WS; Zewail, AH
MLA Citation
Warren, WS, and Zewail, AH. "Multiple phase-coherent laser pulses in optical spectroscopy. II. Applications to multilevel systems." The Journal of Chemical Physics 78.5 (1983): 2298-2311.
Source
scival
Published In
Journal of Chemical Physics
Volume
78
Issue
5
Publish Date
1983
Start Page
2298
End Page
2311

Multiple phase-coherent laser pulses in optical spectroscopy. I. The technique and experimental applications

In this series of papers we report on the generation and application of multiple pulse phase coherent sequences in optical spectroscopy. In this paper the effects of intense pulse trains on systems with only two resonant energy levels are analyzed, with particular attention to the effects of extreme inhomogeneous broadening and population depletion to nonresonant levels. It is shown that these effects, which are present in virtually all optical systems, make the simple gyroscopic model of optical coherent transients invalid. Exact calculations show, e.g., that a two-pulse photon echo is not maximized by a 1:2 length ratio for the pulses; that the maximum excited state population is not created by a 180° pulse; and that three equal pulses are almost as effective as a 1:2:1 ratio for producing three pulse echoes. The role of pulse phase is extensively analyzed. Pulse sequences are proposed and experimentally demonstrated which permit optical phase sensitive detection and measurement of ground state relaxation parameters. The experimental results are based on an extension of the acousto-optic modulation and fluoresence detection techniques of Zewail and Orlowski [Zewail et al., Chem. Phys. Lett. 48, 256 (1977); Orlowski et al., ibid 54, 197 (1978)]. The relative merits of fluorescence and transverse polarization detection are discussed, and fluorescence detection is shown to be more generally useful for these new sequences. Finally, composite pulse trains are shown to be capable of substantially increasing the signal available from highly inhomogenously broadened transitions. In paper II we extend the treatment to multilevel systems with some emphasis on solid state applications. © 1983 American Institute of Physics.

Authors
Warren, WS; Zewail, AH
MLA Citation
Warren, WS, and Zewail, AH. "Multiple phase-coherent laser pulses in optical spectroscopy. I. The technique and experimental applications." The Journal of Chemical Physics 78.5 (1983): 2279-2297.
Source
scival
Published In
Journal of Chemical Physics
Volume
78
Issue
5
Publish Date
1983
Start Page
2279
End Page
2297

Simple pulse sequences for selective multiple-quantum excitation

A sixteen pulse sequence which excites only four-quantum transitions in multiple-quantum NMR is shown to give good selectivity on two molecules, benzene and n-butyl bromide. The behavior as pulse sequence parameters are varied is shown to be consistent with coherent averaging theory. Advantages of this new sequence include much lower duty cycles and shorter total duration than can be achieved with previously used selective sequences. Limitations of this approach and extensions to high-quantum selectivity are discussed. © 1982.

Authors
Warren, WS; Pines, A
MLA Citation
Warren, WS, and Pines, A. "Simple pulse sequences for selective multiple-quantum excitation." Chemical Physics Letters 88.4 (1982): 441-443.
Source
scival
Published In
Chemical Physics Letters
Volume
88
Issue
4
Publish Date
1982
Start Page
441
End Page
443

Laser probing of vibrational energy redistribution and dephasing

This paper addresses questions important to the origin of optical dephasing and vibrational energy redistributions in molecules. Several laser techniques are discussed and three major findings are presented. These findings are related to (a) optical dephasing of molecules in the gas phase and in beams, (b) dephasing of high-energy vibrational overtone states of large molecules, and (c) energy randomization and quantum beats in large molecules (anthracene) excited by picosecond pulses and cooled by supersonic jet expansion. © 1982 American Chemical Society.

Authors
Zewall, A; Lambert, W; Felker, P; Perry, J; Warren, W
MLA Citation
Zewall, A, Lambert, W, Felker, P, Perry, J, and Warren, W. "Laser probing of vibrational energy redistribution and dephasing." Journal of Physical Chemistry 86.7 (1982): 1184-1192.
Source
scival
Published In
Journal of Physical Chemistry
Volume
86
Issue
7
Publish Date
1982
Start Page
1184
End Page
1192

Optical analogs of NMR phase coherent multiple pulse spectroscopy

Authors
Warren, WS; Zewail, AH
MLA Citation
Warren, WS, and Zewail, AH. "Optical analogs of NMR phase coherent multiple pulse spectroscopy." The Journal of Chemical Physics 75.12 (1981): 5956-5958.
Source
scival
Published In
Journal of Chemical Physics
Volume
75
Issue
12
Publish Date
1981
Start Page
5956
End Page
5958

Analogy of multiple-quantum NMR to isotopic spin labeling

The NMR of oriented molecules gives detailed structural information, but isotopic substitution is often required for analysis. An alternative to synthesizing labeled molecules is to observe multiple-quantum spectra. Symmetry arguments show that multiple-quantum transitions yield similar information and that the spectra can be predicted by analogy with labeling experiments. Several examples are shown to illustrate the versatility of this technique for determining molecular conformations and rates of intramolecular processes. © 1981 American Chemical Society.

Authors
Warren, WS; Pines, A
MLA Citation
Warren, WS, and Pines, A. "Analogy of multiple-quantum NMR to isotopic spin labeling." Journal of the American Chemical Society 103.7 (1981): 1613-1617.
Source
scival
Published In
Journal of the American Chemical Society
Volume
103
Issue
7
Publish Date
1981
Start Page
1613
End Page
1617

Experiments on selective excitation of multiple-quantum transitions in NMR spectroscopy

Irradiating a spin system with an appropriate sequence of phase shifted pulses excites only certain orders of multiple-quantum transitions. Using such sequences in preparation and detection produces a large signal/noise enhancement for the multiple-quantum spectra over nonselective excitation, as predicted from theory. In a previous paper the theory was presented in detail. In this paper some aspects of the theory are first outlined briefly. Experimental results are then presented demonstrating four-quantum, six-quantum, and A -symmetry selection in oriented benzene and eight-quantum selection in oriented 1-bromobutane. A six-quantum selective sequence applied to benzene with nonequilibrium initial reduced density matrix proportional to Ix produces one- and five-quantum spectra. The n-quantum signal/noise enhancements are obtained and the selectivity is measured as a function of pulse sequence parameters. The behavior is that expected if one assumes that the limit to selectivity is determined by leading nonselective terms in an average Hamiltonian expansion. © 1981 American Institute of Physics.

Authors
Warren, WS; Pines, A
MLA Citation
Warren, WS, and Pines, A. "Experiments on selective excitation of multiple-quantum transitions in NMR spectroscopy." The Journal of Chemical Physics 74.5 (1981): 2808-2818.
Source
scival
Published In
Journal of Chemical Physics
Volume
74
Issue
5
Publish Date
1981
Start Page
2808
End Page
2818

Theory of selective excitation of multiple-quantum transitions

The question of whether a molecule can be made to absorb and emit photons only in groups of n is treated. Pulse sequences are introduced which in effect selectively induce the absorption of only groups of n photons. This causes only n-quantum transitions even when many other transitions might be resonant. The technique involves repeated phase shifts of 2π/n in the radiation to build up the selected coherences and cancel all other coherences, and is applicable to a wide range of spectroscopic systems. Coherent averaging theory is extended to describe selective sequences and demonstrates that n-quantum selectivity is possible to arbitrarily high order in the average Hamiltonian expansion. High-order selectivity requires many phase shifts, however, and for this reason the residual nonselective effects of sequences which are selective to only a finite order are calculated. Selective sequences are applied to the multiple-quantum NMR of oriented molecules, where in combination with time reversal sequences they produce a much more efficient transfer of the population differences into selected coherences than is obtainable by normal wideband pumping. For example, the 10-quantum transition in a 10-spin system can be enhanced by more than four orders of magnitude. Experiments on selective excitation of the 4-quantum transitions in oriented benzene verify the expected enhancement. © 1980 American Institute of Physics.

Authors
Warren, WS; Weitekamp, DP; Pines, A
MLA Citation
Warren, WS, Weitekamp, DP, and Pines, A. "Theory of selective excitation of multiple-quantum transitions." The Journal of Chemical Physics 73.5 (1980): 2084-2099.
Source
scival
Published In
Journal of Chemical Physics
Volume
73
Issue
5
Publish Date
1980
Start Page
2084
End Page
2099

Selective excitation of multiple-quantum coherence in nuclear magnetic resonance

Wideband selective n-quantum excitation in the NMR of coupled spins is demonstrated for the first time. By a combination of multiple pulse averaging and phase shifts a pure n-quantum excitation operator can be produced (n=2). This allows enhancement of normally weak n-quantum transitions. Selective excitation of the zero- and four-quantum transitions in benzene illustrates this approach. Extensions to selective absorption of only groups of n photons in other regimes of spectroscopy are straight-forward, in principle. © 1979 The American Physical Society.

Authors
Warren, WS; Sinton, S; Weitekamp, DP; Pines, A
MLA Citation
Warren, WS, Sinton, S, Weitekamp, DP, and Pines, A. "Selective excitation of multiple-quantum coherence in nuclear magnetic resonance." Physical Review Letters 43.24 (1979): 1791-1794.
Source
scival
Published In
Physical Review Letters
Volume
43
Issue
24
Publish Date
1979
Start Page
1791
End Page
1794
DOI
10.1103/PhysRevLett.43.1791

Properties and performance of basic designs of infrared interference filters

Results of a computer analysis of the basic designs are given relating their characteristics with their construction and film properties. Data on performance of germanium, silicon monoxide filters are given with environmental conditions and time. The performance of filters in parallel and convergent beams is illustrated. © 1968.

Authors
Warren, SW
MLA Citation
Warren, SW. "Properties and performance of basic designs of infrared interference filters." Infrared Physics 8.1 (1968): 65-78.
Source
scival
Published In
Infrared Physics
Volume
8
Issue
1
Publish Date
1968
Start Page
65
End Page
78
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