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Differential femtosecond coherent Stokes and anti-Stokes Raman spectroscopy  [PDF]
Takuro Ideguchi,Simon Holzner,Ming Yan,Guy Guelachvili,Theodor W. H?nsch,Nathalie Picqué
Physics , 2014,
Abstract: We demonstrate a novel technique of coherent Raman spectroscopy with a femtosecond laser. We apply to a molecular sample a sequence of pairs of ultrashort excitation and probe pulses, with a linearly increasing time delay between the two pulses from one pair to the next. We measure, as a function of the delay, the intensity modulation in the signal resulting from the differential detection of the Stokes and anti-Stokes radiations generated at the sample. The Fourier transform of such time-domain signal reveals the spectrum of the excited vibrational Raman transitions. The experimental proof-of-principle demonstrates high resolution, broad spectral span and suppression of the non-resonant background, as well as sensitivity enhancement due to the differential detection.
Spectral interferometric polarised coherent anti-Stokes Raman spectroscopy  [PDF]
Brad Littleton,Thomas Kavanagh,Frederic Festy,David Richards
Physics , 2013, DOI: 10.1103/PhysRevLett.111.103902
Abstract: We have developed an interferometric implementation of coherent anti-Stokes Raman scattering (CARS) which enables broadband coherent Raman spectroscopy free from non-resonant background (NRB), with a signal strength proportional to concentration. Spectra encode mode symmetry information into the amplitude response which can be directly compared to polarised spontaneous Raman spectra. The method requires only passive polarisation optics and is suitable for a wide range of laser linewidths and pulse durations
Realignment-enhanced coherent anti-Stokes Raman scattering (CARS) and three-dimensional imaging in anisotropic fluids  [PDF]
A. V. Kachynski,A. N. Kuzmin,P. N. Prasad,I. I. Smalyukh
Physics , 2008, DOI: 10.1364/OE.16.010617
Abstract: We apply coherent anti-Stokes Raman Scattering (CARS) microscopy to characterize director structures in liquid crystals.
Noise figure and photon probability distribution in Coherent Anti-Stokes Raman Scattering (CARS)  [PDF]
D. Dimitropoulos,D. R. Solli,R. Claps,B. Jalali
Physics , 2006, DOI: 10.1364/OE.14.011418
Abstract: The noise figure and photon probability distribution are calculated for coherent anti-Stokes Raman scattering (CARS) where an anti-Stokes signal is converted to Stokes. We find that the minimum noise figure is ~ 3dB.
Lineshapes in coherent anti-Stokes Raman spectra of gases  [PDF]
Michele Marrocco,Emil Nordstrom,Per-Erik Bengtsson
Physics , 2014,
Abstract: We introduce new lineshapes of coherent anti-Stokes Raman spectra of gases by considering realistic nanosecond laser pulses that deviate from the Gaussian representations of their time and spectral envelopes. The analysis suggests that the contribution to the linewidth caused by the interaction with such laser pulses could be erroneously attributed to the intrinsic Raman width if the customary CARS approach, based primarily on the Voigt lineshape, is assumed.
Coherent Anti-Stokes Raman Scattering Heterodyne Interferometry  [PDF]
J. S. Bredfeldt,D. L. Marks,C. Vinegoni,S. Hambir,S. A. Boppart
Physics , 2003,
Abstract: A new interferometric technique is demonstrated for measuring Coherent Anti-Stokes Raman Scattering (CARS) signals. Two forward-directed CARS signals are generated, one in each arm of an interferometer. The deterministic nature of the CARS process allows for these two signals, when spatially and temporally overlapped, to interfere with one another. Heterodyne detection can therefore be employed to increase the sensitivity in CARS signal detection. In addition, nonlinear CARS interferometry will facilitate the use of this spectroscopic technique for molecular contrast in Optical Coherence Tomography (OCT).
Direct imaging of molecular symmetry by coherent anti-Stokes Raman scattering  [PDF]
Carsten Cleff,Alicja Gasecka,Patrick Ferrand,Hervé Rigneault,Sophie Brasselet,Julien Duboisset
Physics , 2015,
Abstract: Nonlinear optical methods, such as coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS), are able to perform label free imaging, with chemical bonds specificity. Here, we demonstrate that the use of circularly polarized light allows to retrieve not only the chemical nature but also the symmetry of the probed sample, in a single shot measurement. Our symmetry-resolved scheme offers simple access to the local organization of vibrational bonds and as a result provides enhanced image contrast for anisotropic samples as well as an improved chemical selectivity. We quantify the local organization of vibrational bonds on crystalline and biological samples, thus providing new information not accessible by spontaneous Raman and SRS techniques. This work stands for a novel symmetry-resolved contrast in vibrational microscopy, with potential application in biological diagnostic.
Influence of the Raman depolarisation ratio on far-field radiation patterns in coherent anti-Stokes Raman scattering (CARS) microscopy  [PDF]
D. Gachet,N. Sandeau,H. Rigneault
Physics , 2006, DOI: 10.2971/jeos.2006.06013
Abstract: We propose a full-vectorial numerical study of far field radiation patterns in coherent anti-Stokes Raman scattering (CARS) microscopy. We emphasis the particular role of the Raman depolarisation ratio of the observed medium and show how it modifies the radiation pattern of thin objects.
Sensitivity of coherent anti-Stokes Raman lineshape to time asymmetry of laser pulses  [PDF]
Michele Marrocco,Emil Nordstr?m,Per-Erik Bengtsson
Physics , 2014, DOI: 10.1364/OL.39.005748
Abstract: We show that coherent anti-Stokes Raman lineshapes do not follow known spectral profiles if the time asymmetry of realistic laser pulses is taken into account. Examples are given for nanosecond and picosecond laser pulses commonly employed in frequency-resolved coherent anti-Stokes Raman scattering. More remarkably, the analysis suggests an effect of line narrowing in comparison to the customary approach, based primarily on the Voigt lineshape.
Detection of Lipid-Rich Prostate Circulating Tumour Cells with Coherent Anti-Stokes Raman Scattering Microscopy  [cached]
Mitra Ranjana,Chao Olivia,Urasaki Yasuyo,Goodman Oscar B
BMC Cancer , 2012, DOI: 10.1186/1471-2407-12-540
Abstract: Background Circulating tumour cells (CTC) are an important indicator of metastasis and associated with a poor prognosis. Detection sensitivity and specificity of CTC in the peripheral blood of metastatic cancer patient remain a technical challenge. Methods Coherent anti-Stokes Raman scattering (CARS) microscopy was employed to examine the lipid content of CTC isolated from the peripheral blood of metastatic prostate cancer patients. CARS microscopy was also employed to evaluate lipid uptake and mobilization kinetics of a metastatic human prostate cancer cell line. Results One hundred CTC from eight metastatic prostate cancer patients exhibited strong CARS signal which arose from intracellular lipid. In contrast, leukocytes exhibited weak CARS signal which arose mostly from cellular membrane. On average, CARS signal intensity of prostate CTC was 7-fold higher than that of leukocytes (P<0.0000001). When incubated with human plasma, C4-2 metastatic human prostate cancer cells exhibited rapid lipid uptake kinetics and slow lipid mobilization kinetics. Higher expression of lipid transport proteins in C4-2 cells compared to non-transformed RWPE-1 and non-malignant BPH-1 prostate epithelial cells further indicated strong affinity for lipid of metastatic prostate cancer cells. Conclusions Intracellular lipid could serve as a biomarker for prostate CTC which could be sensitively detected with CARS microscopy in a label-free manner. Strong affinity for lipid by metastatic prostate cancer cells could be used to improve detection sensitivity and therapeutic targeting of prostate CTC.
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