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Sample records for anti-stokes raman spectroscopy

  1. Vibronic spectroscopy of amorphous materials using higher order, multiresonant coherent anti-Stokes Raman spectroscopya)

    NASA Astrophysics Data System (ADS)

    Hurst, Gregory B.; Wright, John C.

    1992-09-01

    Multiresonant coherent anti-Stokes Raman spectroscopy is performed with three tunable lasers on perylene doped polymethylmethacrylate (PMMA). Sharp vibronic features can be observed in vibronic scans at constant energy from the parent electronic transition when resonance is established within the inhomogeneously broadened electronic band. These features are attributed to the nonlinear line narrowing predicted by Ouellette and Denariez-Roberge for a higher order saturated coherent anti-Stokes Raman process since line narrowing should be absent for four wave mixing coherent anti-Stokes Raman spectroscopy. It is shown that the features are sharply dependent on the presence of a simultaneous vibrational resonance as is also predicted by the higher order coherent anti-Stokes Raman model. Excited state coherent anti-Stokes Raman spectroscopy with resonance enhancement from higher singlet states does not contribute to the narrow features since such a process would not have vibrational resonances. Conventional two laser coherent anti-Stokes Raman shows only a weak line at the vibronic transition.

  2. Molecular vibrational dynamics in water studied by femtosecond coherent anti-Stokes Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhao, Yang; Zhang, Sheng; Zhou, Boyang; Dong, Zhiwei; Chen, Deying; Zhang, Zhonghua; Xia, Yuanqin

    2014-10-01

    We utilized femtosecond time-resolved coherent anti-Stokes Raman spectroscopy (CARS) to study the ultrafast vibrational dynamics in distilled water at room temperature. The CARS signals from the broad OH-stretching modes between 3100 cm-1 and 3700 cm-1 were obtained and analyzed. The dephasing times of four Raman modes in water were detected and compared.

  3. Coherent anti-stokes Raman spectroscopy system for point temperature and major species concentration measurement

    SciTech Connect

    Singh, J.P.; Yueh, Fang-Yu

    1993-10-01

    The Coherent anti-Stokes Raman Spectroscopy system (CARS) has been developed as a laser-based, advanced, combustion-diagnostic technique to measure temperature and major species concentration. Principles of operation, description of the system and its capabilities, and operational details of this instrument are presented in this report.

  4. Single-pulse coherent anti-Stokes Raman spectroscopy via fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Oh, Seung Ryeol; Park, Joo Hyun; Kwon, Won Sik; Kim, Jin Hwan; Kim, Kyung-Soo; Lee, Jae Yong; Kim, Soohyun

    2016-03-01

    Fiber Bragg grating is used in a variety of applications. In this study, we suggest compact, cost-effective coherent anti- Stokes Raman spectroscopy which is based on the pulse shaping methods via commercialized fiber Bragg grating. The experiment is performed incorporating a commercialized femtosecond pulse laser system (MICRA, Coherent) with a 100 mm length of 780-HP fiber which is inscribed 50 mm of Bragg grating. The pump laser for coherent anti-Stokes Raman spectroscopy has a bandwidth of 90 nm and central wavelength of 815 nm with a notch shaped at 785 nm. The positive chirped pulse is compensated by chirped mirror set. We compensate almost 14000 fs2 of positive group delay dispersion for the transform-limited pulse at the sample position. The pulse duration was 15 fs with average power of 50 mW, and showed an adequate notch shape. Finally, coherent anti-Stokes Raman signals are observed using a spectrometer (Jobin Yvon Triax320 and TE-cooled Andor Newton EMCCD). We obtained coherent anti-Stokes Raman signal of acetone sample which have Raman peak at the spectral finger-print region. In conclusion, the proposed method is more simple and cost-effective than the methods of previous research which use grating pairs and resonant photonic crystal slab. Furthermore, the proposed method can be used as endoscope application.

  5. Detection of Neutral Species in Silane Plasma Using Coherent Anti-Stokes Raman Spectroscopy

    NASA Astrophysics Data System (ADS)

    Hata, Nobuhiro; Matsuda, Akihisa; Tanaka, Kazunobu; Kajiyama, Koichi; Moro, Norio; Sajiki, Kazuaki

    1983-01-01

    Coherent Anti-Stokes Raman Spectroscopy (CARS) has been employed for the first time to investigate silane (SiH4) glow-discharge plasma. By measuring ν1 vibrational line of silane as a function of position between the two electrodes, spatial distribution of silane (number density) in the (bulk) plasma has been determined for various gas pressures. It has been demonstrated that CARS is an excellent diagnostic tool for a chemically-active plasma such as silane-based glow discharge.

  6. Femtosecond Coherent Anti-Stokes Raman Spectroscopy (CARS) As Next Generation Nonlinear LIDAR Spectroscopy and Microscopy

    SciTech Connect

    Ooi, C. H. Raymond

    2009-07-10

    Nonlinear spectroscopy using coherent anti-Stokes Raman scattering and femtosecond laser pulses has been successfully developed as powerful tools for chemical analysis and biological imaging. Recent developments show promising possibilities of incorporating CARS into LIDAR system for remote detection of molecular species in airborne particles. The corresponding theory is being developed to describe nonlinear scattering of a mesoscopic particle composed of complex molecules by laser pulses with arbitrary shape and spectral content. Microscopic many-body transform theory is used to compute the third order susceptibility for CARS in molecules with known absorption spectrum and vibrational modes. The theory is combined with an integral scattering formula and Mie-Lorentz formulae, giving a rigorous formalism which provides powerful numerical experimentation of CARS spectra, particularly on the variations with the laser parameters and the direction of detection.

  7. Femtosecond Coherent Anti-Stokes Raman Spectroscopy (CARS) As Next Generation Nonlinear LIDAR Spectroscopy and Microscopy

    NASA Astrophysics Data System (ADS)

    Ooi, C. H. Raymond

    2009-07-01

    Nonlinear spectroscopy using coherent anti-Stokes Raman scattering and femtosecond laser pulses has been successfully developed as powerful tools for chemical analysis and biological imaging. Recent developments show promising possibilities of incorporating CARS into LIDAR system for remote detection of molecular species in airborne particles. The corresponding theory is being developed to describe nonlinear scattering of a mesoscopic particle composed of complex molecules by laser pulses with arbitrary shape and spectral content. Microscopic many-body transform theory is used to compute the third order susceptibility for CARS in molecules with known absorption spectrum and vibrational modes. The theory is combined with an integral scattering formula and Mie-Lorentz formulae, giving a rigorous formalism which provides powerful numerical experimentation of CARS spectra, particularly on the variations with the laser parameters and the direction of detection.

  8. Study of high-temperature multiplex HCl coherent anti-Stokes Raman spectroscopy spectra

    SciTech Connect

    Singh, J.P.; Yueh, F.Y.; Kao, W.; Cook, R.L. )

    1993-02-20

    A feasibility study of temperature measurement with multiplex HCl coherent anti-Stokes Raman spectroscopy (CARS) is investigated. The HCl CARS spectra of a 100% HCl gas sample are recorded in a quartz sample cell placed in a furnace at 1 atm pressure and at different temperatures. The nonlinear susceptibility of HCl ([chi][sub nr][sup HCl]), which is measured with the present CARS experimental setup, is reported. The experimental spectra are fit by using a library of simulated HCl CARS spectra with a least-squares-fitting program to infer the temperature. The inferred temperatures from HCl CARS spectra are in agreement with thermocouple temperatures.

  9. Width-Increased Dual-Pump Enhanced Coherent Anti-Stokes Raman Spectroscopy (WIDECARS)

    NASA Technical Reports Server (NTRS)

    Tedder, Sarah A.; Danehy, Paul M.; Cutler, Andrew D.

    2010-01-01

    WIDECARS is a dual-pump coherent anti-Stokes Raman Spectroscopy technique that is capable of simultaneously measuring temperature and species mole fractions of N2, O2, H2, C2H4, CO, and CO2. WIDECARS is designed for measurements of all the major species (except water) in supersonic combustion flows fueled with hydrogen and hydrogen/ethylene mixtures. The two lowest rotational energy levels of hydrogen detectable by WIDECARS are H2 S(3) and H2 S(4). The detection of these lines gives the system the capability to measure temperature and species concentrations in regions of the flow containing pure hydrogen fuel at room temperature.

  10. Diagnostics of silane and germane radio frequency plasmas by coherent anti-Stokes Raman spectroscopy

    NASA Technical Reports Server (NTRS)

    Perry, Joseph W.; Shing, Y. H.; Allevato, C. E.

    1988-01-01

    In situ plasma diagnostics using coherent anti-Stokes Raman spectroscopy have shown different dissociation characteristics for GeH4 and SiH4 in radio frequency (rf) plasma-enhanced chemical vapor deposition of amorphous silicon germanium alloy (a-SiGe:H) thin films. The GeH4 dissociation rate in rf plasmas is a factor of about 3 larger than that of SiH4. Plasma diagnostics have revealed that the hydrogen dilution of the SiH4 and GeH4 mixed plasma plays a critical role in suppressing the gas phase polymerization and enhancing the GeH4 dissociation.

  11. Diagnostics of silane and germane radio frequency plasmas by coherent anti-Stokes Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Perry, Joseph W.; Shing, Y. H.; Allevato, C. E.

    1988-06-01

    In situ plasma diagnostics using coherent anti-Stokes Raman spectroscopy have shown different dissociation characteristics for GeH4 and SiH4 in radio frequency (rf) plasma-enhanced chemical vapor deposition of amorphous silicon germanium alloy (a-SiGe:H) thin films. The GeH4 dissociation rate in rf plasmas is a factor of about 3 larger than that of SiH4. Plasma diagnostics have revealed that the hydrogen dilution of the SiH4 and GeH4 mixed plasma plays a critical role in suppressing the gas phase polymerization and enhancing the GeH4 dissociation.

  12. Coherent Anti-Stokes Raman Spectroscopy of Radio-Frequency Discharge Plasmas of Silane and Disilane

    NASA Astrophysics Data System (ADS)

    Hata, Nobuhiro; Matsuda, Akihisa; Tanaka, Kazunobu

    1986-01-01

    Coherent anti-Stokes Raman spectroscopy has been employed for the diagnosis of rf discharges of silane (SiH4) and disilane (Si2H6). The signal intensities from silane and disilane have been measured as a function of time after switching on the rf power supplied to SiH4 and Si2H6 gas in a closed reaction chamber. From this measurement, the loss rates of silane and disilane have been determined directly as functions of the rf-power density and gas pressure for the first time. The rate of formation of SiH4 in disilane discharge plasmas has also been determined.

  13. Single pulse phase-control interferometric coherent anti-StokesRaman scattering spectroscopy (CARS)

    SciTech Connect

    Lim, Sang-Hyun; Caster, Allison G.; Leone, Stephen R.

    2005-09-28

    In coherent anti-Stokes Raman scattering spectroscopy (CARS) experiments, usually the amplitude of the signal is measured and the phase information is lost. With a polarization- and phase-controlled pulse shaping technique, the relative phase between the resonant and non-resonant CARS signals is controlled, and spectral interferometry is performed without an interferometer. Both the real and imaginary parts of the background-free resonant CARS spectrum are measured via spectral interferometry between the resonant and non-resonant signals from the same sample. The resonant signal is amplified significantly by homodyne mixing with the non-resonant signal as a local oscillator, greatly improving the detection limit.

  14. Molecular vibrational dynamics in polyvinyl alcohol studied by femtosecond coherent anti-stokes Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Kozai, T.; Yamashita, S.; Hirochi, K.; Miyagawa, H.; Tsurumachi, N.; Koshiba, S.; Nakanishi, S.; Itoh, H.

    2012-11-01

    We have performed femtosecond time-resolved coherent anti-stokes Raman spectroscopy (CARS) to study the vibrational dynamics in polyvinyl alcohol (PVA) film. We observed femtosecond coherent vibrational relaxation and CARS signal beats in PVA at room temperature. We found that the coherent vibrational relaxation of anti-symmetric CH2 stretching modes in PVA is faster than that of symmetric modes, probably due to faster vibrational energy transfer. The coherent vibrational relaxation of OH stretching modes was observed to be slower than that of CH2 modes, because OH stretching modes have less resonant energy transfer rate compared to CH2 modes.

  15. Pure rotational coherent anti-Stokes Raman spectroscopy in mixtures of CO and N2.

    PubMed

    Afzelius, Mikael; Brackmann, Christian; Vestin, Fredrik; Bengtsson, Per-Erik

    2004-12-20

    We present a model for quantitative measurements in binary mixtures of nitrogen and carbon monoxide by the use of dual-broadband rotational coherent anti-Stokes Raman spectroscopy. The model has been compared with experimental rotational coherent anti-Stokes Raman scattering spectra recorded within the temperature range of 294-702 K. Temperatures and concentrations were evaluated by spectral fits using libraries of theoretically calculated spectra. The relative error of the temperature measurements was 1-2%, and the absolute error of the CO concentration measurements was <0.5% for temperatures < or =600 K. For higher temperatures, the gas composition was not chemically stable, and we observed a conversion of CO to CO2. The influence of important spectroscopic parameters such as the anisotropic polarizability and Raman line-broadening coefficients are discussed in terms of concentration measurements. In particular, it is shown that the CO concentration measurement was more accurate if N2-CO and CO-N2 line-broadening coefficients were included in the calculation. The applicability of the model for quantitative flame measurements is demonstrated by measuring CO concentrations in ethylene/air flames. PMID:15646786

  16. Next generation hazard detection via ultrafast coherent anti-Stokes Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Brady, John J.; Pellegrino, Paul M.

    2013-05-01

    Multiplex coherent anti-Stokes Raman spectroscopy (MCARS) is used to detect an explosive precursor material and two chemical warfare simulants. The spectral bandwidth of the femtosecond laser pulse used in these studies is sufficient to coherently and simultaneously drive all the vibrational modes in the molecule of interest. The research performed here demonstrates that MCARS has the capability to detect an explosive precursor (e.g., acetone) and hazardous materials, such as dimethyl methylphosphonate and 2-chloroethyl methyl sulfide (a sarin and a mustard gas chemical warfare simulant, respectively), with high specificity. Evidence shows that MCARS is capable of overcoming common the sensitivity limitations of spontaneous Raman scattering, thus allowing for the detection of the target material in milliseconds with standard USB spectrometers as opposed to seconds with intensified spectrometers. The exponential increase in the number of scattered photons suggests that the MCARS technique may be capable of overcoming range detection challenges common to spontaneous Raman scattering.

  17. Analysis of organic pollutant degradation in pulsed plasma by coherent anti-Stokes Raman spectroscopy

    SciTech Connect

    Bratescu, Maria Antoneta; Hieda, Junko; Umemura, Tomonari; Saito, Nagahiro; Takai, Osamu

    2011-05-15

    The degradation of p-benzoquinone (p-BQ) in water was investigated by the coherent anti-Stokes Raman spectroscopy (CARS) method, in which the change of the anti-Stokes signal intensity corresponding to the vibrational transitions of the molecule is monitored during and after solution plasma processing (SPP). In the beginning of SPP treatment, the CARS signal intensity of the ring vibrational molecular transitions at 1233 and 1660 cm{sup -1} increases under the influence of the electric field of the plasma, depending on the delay time between the plasma pulse and the laser firing pulse. At the same time, the plasma contributes to the degradation of p-BQ molecules by generating hydrogen and hydroxyl radicals, which decompose p-BQ into different carboxylic acids. After SPP, the CARS signal intensity of the vibrational bands of p-BQ ceased and the degradation of p-BQ was confirmed by UV-visible absorption spectroscopy and liquid chromatography analysis.

  18. Anti-Stokes Raman laser

    SciTech Connect

    White, J.C.; Henderson, D.

    1982-02-01

    The first observation of nonresonant, stimulated anti-Stokes Raman emission is reported. A metastable T1 (6rho /sup 2/P/sup 0//sub 3/2/) inversion is created by selective photodissociation of TlCl. Raman scattering from the Tl metastable state to ground using 532- and 355-nm pump lasers resulted in stimulated emission at 376 and 278 nm, respectively. Conversion efficiencies up to 10% are reported.

  19. Real-time detection of bacterial spores using coherent anti-Stokes Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Dogariu, A.; Goltsov, A.; Pestov, D.; Sokolov, A. V.; Scully, M. O.

    2008-02-01

    We demonstrate a realistic method for detection of anthrax-type spores in real time based on their chemical fingerprints using coherent anti-Stokes Raman scattering. Specifically, we demonstrate that coherent Raman scattering can be used to successfully identify spores with high accuracy and high selectivity in less than 50ms.

  20. Silane thermometry in radio-frequency discharge plasma by coherent anti-Stokes Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Hata, Nobuhiro; Matsuda, Akihisa; Tanaka, Kazunobu

    1986-03-01

    The rotational temperature of silane molecules in a flowing gas as well as in a radio-frequency discharge plasma of silane has been determined by the analysis of its coherent anti-Stokes Raman spectra. The ν1 Q-band coherent anti-Stokes Raman spectra of silane have been measured under different conditions such as discharge off, discharge on, and electrode heating, and fitted to theoretically calculated curves for various rotational temperatures using a nonlinear least-squares method. The results have shown that discharge power as well as electrode heating increase the rotational temperature of SiH4.

  1. Coherent anti-Stokes Raman spectroscopy utilizing phase mismatched cascaded quadratic optical interactions in nonlinear crystals

    PubMed Central

    Petrov, Georgi I.; Zhi, Miaochan; Yakovlev, Vladislav V.

    2013-01-01

    We experimentally investigated the nonlinear optical interaction between the instantaneous four-wave mixing and the cascaded quadratic frequency conversion in commonly used nonlinear optical KTP and LiNbO3 with the aim of a possible background suppression of the non-resonant background in coherent anti-Stokes Raman scattering. The possibility of background-free heterodyne coherent anti-Stokes Raman scattering microspectroscopy is investigated at the interface formed by a liquid (isopropyl alcohol) and a nonlinear crystal (LiNbO3). PMID:24514791

  2. Investigation of a simulated tritium plasma using Coherent Anti-Stokes Raman Spectroscopy

    SciTech Connect

    Siwecki, S.A.; Dosser, L.R.

    1989-11-30

    The production of T{sup {minus}} in a tritium beta plasma occurs when a thermal electron and a tritium molecule undergo a dissociative attachment reaction. A measurement of the T{sup {minus}} concentration in tritium indicated that it was high, but further analysis showed this result to be inconclusive. It was then suggested that a high T{sup {minus}} concentration could arise if tritium molecules undergoing dissociative attachment were vibrationally excited. The reaction rate for such a process is orders of magnitude higher when vibrationally excited molecules are involved. Both the thermal electron and the vibrationally excited molecules are a result of the energy supplied by the beta decay of tritium. A search for the presence of vibrationally excited molecules in a simulated tritium plasma was undertaken using Coherent Anti-Stokes Raman Spectroscopy. The results showed no presence of vibrationally excited molecules and therefore did not support the foregoing hypothesis. 13 refs., 10 figs.

  3. Calculation of collisionally narrowed coherent anti-Stokes Raman spectroscopy spectra

    SciTech Connect

    Koszykowski, M.L.; Farrow, R.L.; Palmer, R.E.

    1985-10-01

    High-resolution coherent anti-Stokes Raman spectroscopy spectra of the N/sub 2/ Q branch at 294 K have been obtained at 1, 5, and 10 atm. Even at 1-atm pressure, disagreements with spectra calculated using the isolated line approximation were observed, indicating the importance of collisional narrowing effects in describing these spectra. A method of using the full G-matrix approach for the calculation of these spectra that is both exact and computationally efficient (requiring only one matrix diagonalization and inversion per spectrum) is discussed. Excellent agreement with experimental data is obtained using this method and a simple exponential gap model for the off-diagonal G-matrix elements.

  4. Coherent anti-Stokes Raman spectroscopy temperature measurements in a hydrogen-fueled supersonic combustor

    NASA Technical Reports Server (NTRS)

    Smith, Michael W.; Jarrett, Olin, Jr.; Antcliff, Richard R.; Northam, G. B.; Cutler, Andrew D.; Taylor, David J.

    1993-01-01

    Coherent anti-Stokes Raman spectroscopy (CARS) thermometry has been used to obtain static temperature cross sections in a three-dimensional supersonic combustor flowfield. Data were obtained in three spanwise planes downstream of a single normal fuel injector which was located downstream of a rearward-facing step. The freestream flow was nominally Mach 2 and was combustion heated to a total temperature of 1440 K (yielding a static temperature of about 800 K in the freestream) to simulate the inflow to a combustor operating at a flight Mach number of about 5.4. Since a broadband probe laser was used an instantaneous temperature sample was obtained with each laser shot at a repetition rate of 10 Hz. Thus root-mean-square (rms) temperatures and temperature probability density functions (pdf's) were obtained in addition to mean temperatures.

  5. Multiplex coherent anti-Stokes Raman spectroscopy by use of a nearly degenerate broadband optical parametric oscillator.

    PubMed

    Chen, P C; Joyner, C C; Burns-Kaurin, M

    1999-09-20

    Optical parametric oscillators (OPO's) provide low-maintenance solid-state alternatives to dye lasers. We present results from use of a nearly degenerate broadband OPO for multiplex coherent anti-Stokes Raman spectroscopy. The system described is capable of generating spectra that cover a range of approximately 1000 cm(-1). PMID:18324105

  6. Detection of Bacillus subtilis spores in water by means of broadband coherent anti-Stokes Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Petrov, Georgi I.; Yakovlev, Vladislav V.; Sokolov, Alexei V.; Scully, Marlan O.

    2005-11-01

    Broadband coherent anti-Stokes Raman scattering (CARS) spectroscopy is used for detection of bacterial spores in aqueous solution. Polarization CARS spectroscopy is employed to suppress the non-resonant background. CARS spectrum recorded in the spectral region from 700 to 1900 cm-1 exhibits all the characteristic features of spontaneous Raman spectrum taken for a solid powder and resembles that one of the dipicolinic acid, which is considered to be the major component of bacterial spores, including anthrax.

  7. Coherent anti-Stokes Raman spectroscopy - Spectra of water vapor in flames

    NASA Technical Reports Server (NTRS)

    Hall, R. J.; Shirley, J. A.; Eckbreth, A. C.

    1979-01-01

    The results of experimental measurements of the coherent anti-Stokes Raman spectra of water vapor in flames are reported. A pulsed, frequency-doubled neodymium laser was used to supply the pump beam and to pump a dye laser to provide a broadband Stokes beam at 6600 A. Spectra were obtained in the postflame region of a premixed methane-air flame in the Raman frequency shift region of the symmetric stretch mode (3651.7 kaysers) at an approximate temperature of 1675 K. A theoretical calculation of the coherent anti-Stokes Raman spectrum of water vapor at this temperature was made, taking into account only isotropic Q-branch transitions, and using the energy level data of Floud et al. (1976). The theoretical prediction is shown essentially to reproduce all qualitative features of the experimental spectrum, and to exhibit a strong temperature dependence.

  8. Coherent anti-stokes Raman spectroscopy for detecting explosives in real time

    NASA Astrophysics Data System (ADS)

    Dogariu, Arthur; Pidwerbetsky, Alex

    2012-06-01

    We demonstrate real-time stand-off detection and imaging of trace explosives using collinear, backscattered Coherent Anti-Stokes Raman Spectroscopy (CARS). Using a hybrid time-resolved broad-band CARS we identify nanograms of explosives on the millisecond time scale. The broad-band excitation in the near-mid-infrared region excites the vibrational modes in the fingerprint region, and the time-delayed probe beam ensures the reduction of any non-resonant contributions to the CARS signal. The strong coherent enhancement allows for recording Raman spectra in real-time. We demonstrate stand-off detection by acquiring, analyzing, and identifying vibrational fingerprints in real-time with very high sensitivity and selectivity. By extending the focused region from a 100-micron sized spot to a 5mm long line we can obtain the spectral information from an extended region of the remote target with high spatial resolution. We demonstrate fast hyperspectral imaging by one-dimensional scanning of the Line-CARS. The three-dimensional data structure contains the vibrational spectra of the target at each sampled location, which allows for chemical mapping of the remote target.

  9. Combined spontaneous Stokes and coherent anti-Stokes Raman scattering spectroscopy

    NASA Astrophysics Data System (ADS)

    Becker, Karina; Kiefer, Johannes

    2016-05-01

    The simultaneous determination of multiple parameters is the key in the characterization of processes and materials that change with time. In combustion environments, the combined measurement of temperature and chemical composition is particularly desirable. In the present work, possible approaches for the simultaneous application of spontaneous Raman scattering (RS) and coherent anti-Stokes Raman scattering (CARS) spectroscopy are proposed and analyzed. While RS provides concentration information of all major species, vibrational CARS is a highly accurate thermometry tool at flame conditions. Five experimentally feasible CARS-RS schemes are identified and discussed with respect to signal intensity, measurement volume, and experimental complexity. From this analysis, one scheme was found to be the best option. It utilizes a broadband dye laser centered at 852 nm as a pump and the fundamental 1064-nm radiation of the Nd:YAG as Stokes laser. The third harmonic is used as CARS probe and RS laser. The experimentally most elegant scheme replaces the third harmonic in the above scheme by the second harmonic hence involving the smallest number of optical components in the setup.

  10. Raman spectroscopy and coherent anti-Stokes Raman scattering imaging: prospective tools for monitoring skeletal cells and skeletal regeneration

    PubMed Central

    Moura, Catarina Costa; Tare, Rahul S.; Oreffo, Richard O. C.; Mahajan, Sumeet

    2016-01-01

    The use of skeletal stem cells (SSCs) for cell-based therapies is currently one of the most promising areas for skeletal disease treatment and skeletal tissue repair. The ability for controlled modification of SSCs could provide significant therapeutic potential in regenerative medicine, with the prospect to permanently repopulate a host with stem cells and their progeny. Currently, SSC differentiation into the stromal lineages of bone, fat and cartilage is assessed using different approaches that typically require cell fixation or lysis, which are invasive or even destructive. Raman spectroscopy and coherent anti-Stokes Raman scattering (CARS) microscopy present an exciting alternative for studying biological systems in their natural state, without any perturbation. Here we review the applications of Raman spectroscopy and CARS imaging in stem-cell research, and discuss the potential of these two techniques for evaluating SSCs, skeletal tissues and skeletal regeneration as an exemplar. PMID:27170652

  11. Raman spectroscopy and coherent anti-Stokes Raman scattering imaging: prospective tools for monitoring skeletal cells and skeletal regeneration.

    PubMed

    Moura, Catarina Costa; Tare, Rahul S; Oreffo, Richard O C; Mahajan, Sumeet

    2016-05-01

    The use of skeletal stem cells (SSCs) for cell-based therapies is currently one of the most promising areas for skeletal disease treatment and skeletal tissue repair. The ability for controlled modification of SSCs could provide significant therapeutic potential in regenerative medicine, with the prospect to permanently repopulate a host with stem cells and their progeny. Currently, SSC differentiation into the stromal lineages of bone, fat and cartilage is assessed using different approaches that typically require cell fixation or lysis, which are invasive or even destructive. Raman spectroscopy and coherent anti-Stokes Raman scattering (CARS) microscopy present an exciting alternative for studying biological systems in their natural state, without any perturbation. Here we review the applications of Raman spectroscopy and CARS imaging in stem-cell research, and discuss the potential of these two techniques for evaluating SSCs, skeletal tissues and skeletal regeneration as an exemplar. PMID:27170652

  12. Tracking Bulk and Interfacial Diffusion Using Multiplex Coherent Anti-Stokes Raman Scattering Correlation Spectroscopy.

    PubMed

    Bailey, Karen A; Schultz, Zachary D

    2016-07-14

    Multiplex coherent anti-Stokes Raman scattering correlation spectroscopy (CARS-CS) is shown as a label-free, chemically specific approach for monitoring the molecular mobility of particles in solution and at interfaces on the millisecond time scale. The CARS spectral range afforded by broadband excitation facilitates a quantitative measurement for the number of particles in the focal volume, whereas the autocorrelation of spectral data elucidates dynamic events, such as diffusion. The measured diffusion coefficients for polymer beads ranging from 100 nm to 1.1 μm in diameter are on the order of 10(-8)-10(-9) cm(2)/s, in good agreement with predicted Stokes-Einstein values. Diffusion at different interfaces shows particles are fastest in bulk medium, marginally slower at the liquid/glass interface, and 1.5-2 times slower rate at the air/liquid interface. Multivariate curve resolution analysis of distinct spectral features in multiplex CARS measurement distinguishes different composition lipid vesicles in a mixture diffusing through the focal volume. The observed diffusion is consistent with results obtained from single particle tracking experiments. This work demonstrates the utility of multiplex CARS correlation spectroscopy for monitoring particle diffusion from different chemical species across diverse interfaces. PMID:27322504

  13. Development of multipoint vibrational coherent anti-Stokes Raman spectroscopy for flame applications.

    PubMed

    Afzelius, Mikael; Bengtsson, Per-Erik; Bood, Joakim; Brackmann, Christian; Kurtz, Alfred

    2006-02-20

    A novel technique for coherent anti-Stokes Raman spectroscopy (CARS) measurements in multiple points is presented. In a multipass cavity the pump and Stokes laser beams are multiply reflected and refocused into a measurement volume with an adjustable number of separated points along a line. This optical arrangement was used in a vibrational CARS setup with planar BOXCARS phase-matching configuration. The CARS spectra from spatially separated points were recorded at different heights on a CCD camera. Measurements of temperature profiles were carried out in the burned gas zone of a premixed one-dimensional flame to demonstrate the applicability of this method for temperature measurements in high-temperature regions. The ability to measure in flames with strong density gradients was demonstrated by simultaneous measurements of Q-branch spectra of N2 and CO in a Wolfhard-Parker burner flame. Interference phenomena found in multipoint spectra are discussed, and possible solutions are proposed. Merits and limitations of the technique are discussed. PMID:16523780

  14. CARS (coherent anti-Stokes Raman spectroscopy) detection of gaseous species for diamond deposition process

    SciTech Connect

    Roman, W.C.; Eckbreth, A.C. )

    1989-01-01

    In order to understand the complicated chemical and physical processes that occur during the deposition of hard face coatings such as diamond, diagnostics that are remote, nonintrusive and sensitive to potential chemical species are necessary. One particularly promising approach is coherent anti-Stokes Raman spectroscopy (CARS) useful for measurements of temperature and species concentrations. Results to be described will include CARS measurements on a PACVD reactor used for depositing high quality diamond films. A mixture of acetylene (C{sub 2}H{sub 2}) and Argon, tested over a range of total pressures down to 0.1 Torr, was used to calibrate the CARS system. With the existing CARS system, detectivity of C{sub 2}H{sub 2} to 5 mtorr was demonstrated. This paper describes details of the scanned narrowband colinear CARS system and examples of CARS spectra obtained for CH{sub 4} and C{sub 2}H{sub 2} species under rf PACVD diamond deposition conditions and also using an alternate filament assisted technique.

  15. Coherent Anti-Stokes Raman Spectroscopy (CARS) Measurements in Supersonic Combustors at NASA Langley Research Center

    NASA Technical Reports Server (NTRS)

    Danehy, Paul M.; OByrne, Sean B.; Tedder, Sarah A.; Cutler, Andrew D.

    2005-01-01

    This paper describes the recent use of coherent anti-Stokes Raman spectroscopy (CARS) to study supersonic combustion at NASA Langley Research Center. CARS is a nonlinear optical measurement technique used to measure temperature and species mole fractions remotely in harsh environments. A CARS system has been applied to two different combustor geometries at NASA Langley. Both experiments used the same vitiated wind-tunnel facility to create an air flow that simulates flight at Mach numbers of 6 and 7 for the combustor inlet and both experiments used hydrogen fuel. In the first experiment, the hydrogen was injected supersonically at a 30-degree angle with respect to the incoming flow. In the second experiment, the hydrogen was injected sonically at normal incidence. While these injection schemes produced significantly different flow features, the CARS method provided mean temperature, N2, O2 and H2 maps at multiple downstream locations for both. The primary aim of these measurements was to provide detailed flowfield information for computational fluid dynamics (CFD) code validation.

  16. Investigation of porous media combustion by coherent anti-Stokes Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Weikl, M. C.; Tedder, S. A.; Seeger, T.; Leipertz, A.

    2010-10-01

    High efficiency, marginal pollutant emissions and low fuel consumption are desirable standards for modern combustion devices. The porous burner technology is a modern type of energy conversion with a strong potential to achieve these standards. However, due to the solid ceramic framework investigation of the thermodynamic properties of combustion, for example temperature, is difficult. The combustion process inside the ceramic structure of a porous burner was experimentally investigated by coherent anti-Stokes Raman spectroscopy (CARS). In this work, we present measurements using dual-pump dual-broadband CARS (DP-DBB-CARS) of temperature and species concentrations inside the reaction and flue gas zone of a porous media burner. Improvements to the setup and data evaluation procedure in contrast to previous measurements are discussed in detail. The results at varied thermal power and stoichiometry are presented. In addition, measurements at a range of radial positions inside a pore are conducted and correlated with the solid structure of the porous foam, which was determined by X-ray computer tomography.

  17. Coherent anti-Stokes Raman spectroscopy of shock-compressed liquid oxygen

    SciTech Connect

    Schmidt, S.C.; Moore, D.S.; Shaw, M.S.; Johnson, J.D.

    1989-01-01

    Vibrational spectra of liquid oxygen, shock compressed to several high-pressure/high-temperature states, were obtained using single- pulse multiplex coherent anti-Stokes Raman scattering (CARS). The experimental spectra were compared to synthetic spectra calculated using a semiclassical model for the CARS intensities and best fit vibrational frequencies, peak Raman susceptibilities, and Raman linewidths. Up to the maximum shock pressure of 9.6 GPa, the vibrational frequencies were found to increase monotonically with pressure. An empirical fit, which could be used as a pressure/temperature/frequency calibration standard, showed that the Raman frequency shifts could be accurately described by linear pressure and temperature dependences. Above /approx/9 GPa, the liquid oxygen opacity at 632.8 nm increased rapidly, presumably because of proximity (collision)-induced absorption. Calculations showed that the induced absorption did not resonantly enhance the CARS spectra, but did attenuate the laser beams and the CARS signals. 33 refs., 2 figs., 1 tab.

  18. Polarization Sensitive Coherent Anti-Stokes Raman Spectroscopy of DCVJ in Doped Polymer

    NASA Astrophysics Data System (ADS)

    Ujj, Laszlo

    2014-05-01

    Coherent Raman Microscopy is an emerging technic and method to image biological samples such as living cells by recording vibrational fingerprints of molecules with high spatial resolution. The race is on to record the entire image during the shortest time possible in order to increase the time resolution of the recorded cellular events. The electronically enhanced polarization sensitive version of Coherent anti-Stokes Raman scattering is one of the method which can shorten the recording time and increase the sharpness of an image by enhancing the signal level of special molecular vibrational modes. In order to show the effectiveness of the method a model system, a highly fluorescence sample, DCVJ in a polymer matrix is investigated. Polarization sensitive resonance CARS spectra are recorded and analyzed. Vibrational signatures are extracted with model independent methods. Details of the measurements and data analysis will be presented. The author gratefully acknowledge the UWF for financial support.

  19. Use of the Gerchberg-Saxton algorithm in optimal coherent anti-Stokes Raman spectroscopy.

    PubMed

    Moore, D S; McGrane, S D; Greenfield, M T; Scharff, R J; Chalmers, R E

    2012-01-01

    We are utilizing recent advances in ultrafast laser technology and recent discoveries in optimal shaping of laser pulses to significantly enhance the stand-off detection of explosives via control of molecular processes at the quantum level. Optimal dynamic detection of explosives is a method whereby the selectivity and sensitivity of any of a number of nonlinear spectroscopic methods are enhanced using optimal shaping of ultrafast laser pulses. We have recently investigated the Gerchberg-Saxton algorithm as a method to very quickly estimate the optimal spectral phase for a given analyte from its spontaneous Raman spectrum and the ultrafast laser pulse spectrum. Results for obtaining selective coherent anti-Stokes Raman spectra (CARS) for an analyte in a mixture, while suppressing the CARS signals from the other mixture components, are compared for the Gerchberg-Saxton method versus previously obtained results from closed-loop machine-learning optimization using evolutionary strategies. PMID:21887605

  20. Coherent Anti-Stokes Raman Spectroscopy (cars) Gas Temperature Measurements in a Monodisperse Combusting Droplet Stream.

    NASA Astrophysics Data System (ADS)

    Zhu, Junyong

    1991-06-01

    This dissertation describes a coherent anti-Stokes Raman spectroscopy (CARS) instrument for spatially and temporally resolved non-intrusive temperature measurements in combustion environments. It presents a detailed description of the CARS system development and standard procedures to perform CARS gas temperature measurements,and procedures to analyze the CARS spectra for temperature determination. The dissertation also applies the CARS apparatus developed to a single monodisperse methanol droplet stream flame to demonstrate synchronous CARS temperature measurements. The measurements correlate the temperature field with the droplet position and give the local characteristics of the combusting droplet stream thermal field. These measurements are not possible with conventional thermal probes due to the perturbation caused by the probes and the poor temporal and spatial resolution. These CARS measurements are the first known non-intrusive characterization of the local temperature field near burning droplets. The experiments use a 50 μm diameter nozzle vibrated by a piezoelectric crystal to generate a monodisperse droplet stream with a droplet diameter of about 150 μm and droplet-to-droplet spacing of 10 droplet diameters. A frequency divider divides the crystal vibration frequency of 10 kHz 1000 times to synchronize the CARS laser firing (~ 10 Hz) with the droplet generation process. The results show that there is a small thermal wake behind each droplet in the stream. The temperature profile measured radially outward from the droplet has a local minimum near the droplet surface, rises to a maximum at about 7 droplet diameters away, and then falls to room temperature at a radial distance of 15 mm (100 droplet diameters). The temperature profile measured between two adjacent droplets on the stream axis is nearly flat, suggesting that individual flames do not surround each droplet. The local effects due to the presence of droplets completely disappear about 15 droplet

  1. Coherent anti-Stokes Raman spectroscopy of shock-compressed liquid carbon monoxide

    SciTech Connect

    Moore, D.S.; Schmidt, S.C.; Shaw, M.S.; Johnson, J.D. )

    1991-10-15

    Vibrational spectra of liquid carbon monoxide shock compressed to several high pressure/high temperature states were recorded using single-pulse multiplex coherent anti-Stokes Raman scattering. Vibrational frequencies, third-order suceptibility ratios, and linewidths are reported for the fundamental and first excited-state transition. The observed vibrational frequency shift with shock pressure was substantially less than that observed previously in nitrogen, implying a significant difference in the details of their inter- and intramolecular potentials. The transition intensity and linewidth data suggest that thermal equilibrium of the vibrational levels is attained in less than 10 ns at these shock pressures, and the vibrational temperatures obtained are comparable to calculated equation-of-state temperatures. The measured linewidths suggest that the vibrational dephasing time decreased to {similar to}2 ps at our highest pressure shock state.

  2. Coherent Anti-stokes Raman Spectroscopy (CARS) of gun propellant flames

    NASA Technical Reports Server (NTRS)

    Mcilwain, M. E.; Harris, L. E.

    1980-01-01

    Temperature measurements were made in a slightly fuel rich, premixed propane/air reference flame and nitrate ester propellant flames burning in air at atmospheric pressure using coherent anti-stokes raman scattering (CARS). Both single and multiple pulse VARS spectra of nitrogen in the reference flame were in good agreement with calculated and reported values. Single pulse CARS nitrogen spectra obtained in the propellant flames were analyzed to give temperatures consistent with values calculated using the NASA-Lewis thermochemical calculation. Comparison of a 0.1 second separated sequence of single pulse CARS spectra indicate turbulent air mixing in these propellant flames. The CARS spectral results demonstrate that temporal and spatially resolved temperature measurements could be determined in transient, turbulent flames.

  3. Quantitative, comparable coherent anti-Stokes Raman scattering (CARS) spectroscopy: correcting errors in phase retrieval

    NASA Astrophysics Data System (ADS)

    Camp, Charles H., Jr.; Lee, Young Jong; Cicerone, Marcus T.

    2016-04-01

    Coherent anti-Stokes Raman scattering (CARS) microspectroscopy has demonstrated significant potential for biological and materials imaging. To date, however, the primary mechanism of disseminating CARS spectroscopic information is through pseudocolor imagery, which explicitly neglects a vast majority of the hyperspectral data. Furthermore, current paradigms in CARS spectral processing do not lend themselves to quantitative sample-to-sample comparability. The primary limitation stems from the need to accurately measure the so-called nonresonant background (NRB) that is used to extract the chemically-sensitive Raman information from the raw spectra. Measurement of the NRB on a pixel-by-pixel basis is a nontrivial task; thus, reference NRB from glass or water are typically utilized, resulting in error between the actual and estimated amplitude and phase. In this manuscript, we present a new methodology for extracting the Raman spectral features that significantly suppresses these errors through phase detrending and scaling. Classic methods of error-correction, such as baseline detrending, are demonstrated to be inaccurate and to simply mask the underlying errors. The theoretical justification is presented by re-developing the theory of phase retrieval via the Kramers-Kronig relation, and we demonstrate that these results are also applicable to maximum entropy method-based phase retrieval. This new error-correction approach is experimentally applied to glycerol spectra and tissue images, demonstrating marked consistency between spectra obtained using different NRB estimates, and between spectra obtained on different instruments. Additionally, in order to facilitate implementation of these approaches, we have made many of the tools described herein available free for download.

  4. Tunable anti-Stokes Raman laser

    SciTech Connect

    White, J.C.

    1984-12-04

    An anti-Stokes Raman laser is disclosed which is tunable over a range of 10-70 cm-/sup 1/. An alkali halide is used as the lasing medium and a metastable halide population inversion is created with respect to the ground state of the halide by selective photodissociation of the alkali halide. A pump laser is then employed to move the population from the metastable state to a region near an intermediate state of the halide. The population subsequently falls back to the initial ground state, thereby creating the anti-Stokes Raman emission. Since the intensity of the photodissociation is directly proportional to the amount of population inversion achieved, and hence, to the region the population may be pumped to, the tuning of the output anti-Stokes Raman lasing is a function of the intensity of the initial photodissoiation.

  5. Diagnostics of a capillary discharge of a CO2 waveguide laser by coherent anti-Stokes Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Vakhterov, A. A.; Iliukhin, A. A.; Konev, Iu. B.; Lipatov, N. I.; Pashinin, P. P.

    1985-01-01

    Experimental results are reported from coherent anti-Stokes Raman spectroscopy (CARS) diagnostic studies of capillary discharge in the CO2:N2:He = 1:1:8 working mixture of a CO2 waveguide laser. The CARS scans were used to characterize the translational temperature of the gas and the vibrational temperatures of the discharge plasma components. The data are vital for identifying anharmonic states which reduce the laser power and working mixture lifetime. Data are furnished on the translational temperature and vibrational temperature as functions of the capillary radius. CARS is concluded to be a valid technique for studying the distribution of pump power among the degrees of freedom of the working mixture components, even when dissociation is occurring.

  6. Two-beam ultrabroadband coherent anti-Stokes Raman spectroscopy for high resolution gas-phase multiplex imaging

    SciTech Connect

    Bohlin, Alexis; Kliewer, Christopher J.

    2014-01-20

    We propose and develop a method for wideband coherent anti-Stokes Raman spectroscopy (CARS) in the gas phase and demonstrate the single-shot measurement of N{sub 2}, H{sub 2}, CO{sub 2}, O{sub 2}, and CH{sub 4}. Pure-rotational and vibrational O-, Q-, and S- branch spectra are collected simultaneously, with high spectral and spatial resolution, and within a single-laser-shot. The relative intensity of the rotational and vibrational signals can be tuned arbitrarily using polarization techniques. The ultrashort 7 fs pump and Stokes pulses are automatically overlapped temporally and spatially using a two-beam CARS technique, and the crossed probe beam allows for excellent spatial sectioning of the probed location.

  7. Dual-soliton Stokes-based background-free coherent anti-Stokes Raman scattering spectroscopy and microscopy.

    PubMed

    Chen, Kun; Wu, Tao; Wei, Haoyun; Li, Yan

    2016-06-01

    We propose an all-fiber-generated, dual-soliton, Stokes-based scheme for background-free coherent anti-Stokes Raman scattering (CARS) under the spectral focusing mechanism. Owing to the strong birefringence and high nonlinearity of a polarization-maintaining PCF (PM-PCF), two soliton pulses can be simultaneously emitted along different eigenpolarization axes and both serve as Stokes pulses, while allowing feasible tunability of frequency distance and temporal interval between them. This proposed scheme, based on an all-fiber light source, exploits a unique combination of slight frequency-shift temporal walk-off of these two solitons to achieve efficient suppression of the nonresonant background and beat the inaccessibility and complexity of the excitation source. Capability is experimentally demonstrated by background-free CARS spectroscopy and unambiguous CARS microscopy in the fingerprint region. PMID:27244431

  8. Temperature measurements in reacting flows by time-resolved femtosecond coherent anti-Stokes Raman scattering (fs-CARS) spectroscopy

    NASA Astrophysics Data System (ADS)

    Roy, Sukesh; Kinnius, Paul J.; Lucht, Robert P.; Gord, James R.

    2008-01-01

    Time-resolved femtosecond coherent anti-Stokes Raman scattering (fs-CARS) spectroscopy of the nitrogen molecule is used for the measurement of temperature in atmospheric-pressure, near-adiabatic, hydrogen-air diffusion flames. The initial frequency-spread dephasing rate of the Raman coherence induced by the ultrafast (∼85 fs) Stokes and pump beams is used as a measure of gas-phase temperature. This initial frequency-spread dephasing rate of the Raman coherence is completely independent of collisions and depends only on the frequency spread of the Raman transitions at different temperatures. A simple theoretical model based on the assumption of impulsive excitation of Raman coherence is used to extract temperatures from time-resolved fs-CARS experimental signals. The extracted temperatures from fs-CARS signals are in excellent agreement with the theoretical temperatures calculated from an adiabatic equilibrium calculation. The estimated absolute accuracy and the precision of the measurement technique are found to be ±40 K and ±50 K, respectively, over the temperature range 1500-2500 K.

  9. Coherent Anti-Stokes Raman Scattering Spectroscopy of Single Molecules in Solution

    SciTech Connect

    Sunney Xie, Wei Min, Chris Freudiger, Sijia Lu

    2012-01-18

    During this funding period, we have developed two breakthrough techniques. The first is stimulated Raman scattering microscopy, providing label-free chemical contrast for chemical and biomedical imaging based on vibrational spectroscopy. Spontaneous Raman microscopy provides specific vibrational signatures of chemical bonds, but is often hindered by low sensitivity. We developed a three-dimensional multiphoton vibrational imaging technique based on stimulated Raman scattering (SRS). The sensitivity of SRS imaging is significantly greater than that of spontaneous Raman microscopy, which is achieved by implementing high-frequency (megahertz) phase-sensitive detection. SRS microscopy has a major advantage over previous coherent Raman techniques in that it offers background-free and readily interpretable chemical contrast. We demonstrated a variety of biomedical applications, such as differentiating distributions of omega-3 fatty acids and saturated lipids in living cells, imaging of brain and skin tissues based on intrinsic lipid contrast, and monitoring drug delivery through the epidermis. This technology offers exciting prospect for medical imaging. The second technology we developed is stimulated emission microscopy. Many chromophores, such as haemoglobin and cytochromes, absorb but have undetectable fluorescence because the spontaneous emission is dominated by their fast non-radiative decay. Yet the detection of their absorption is difficult under a microscope. We use stimulated emission, which competes effectively with the nonradiative decay, to make the chromophores detectable, as a new contrast mechanism for optical microscopy. We demonstrate a variety of applications of stimulated emission microscopy, such as visualizing chromoproteins, non-fluorescent variants of the green fluorescent protein, monitoring lacZ gene expression with a chromogenic reporter, mapping transdermal drug distribu- tions without histological sectioning, and label-free microvascular

  10. Label-Free Fluctuation Spectroscopy Based on Coherent Anti-Stokes Raman Scattering from Bulk Water Molecules.

    PubMed

    Rabasovic, M D; Sisamakis, E; Wennmalm, S; Widengren, J

    2016-04-01

    Nanoparticles (NPs) and molecules can be analyzed by inverse fluorescence correlation spectroscopy (iFCS) as they pass through an open detection volume, displacing fractions of the fluorescence-emitting solution in which they are dissolved. iFCS does not require the NPs or molecules to be labeled. However, fluorophores in μm-mm concentrations are needed for the solution signal. Here, we instead use coherent anti-Stokes Raman scattering (CARS) from plain water molecules as the signal from the solution. By this fully label-free approach, termed inverse CARS-based correlation spectroscopy (iCARS-CS), NPs that are a few tenths of nm in diameter and at pM concentrations can be analyzed, and their absolute volumes/concentrations can be determined. Likewise, lipid vesicles can be analyzed as they diffuse/flow through the detection volume by using CARS fluctuations from the surrounding water molecules. iCARS-CS could likely offer a broadly applicable, label-free characterization technique of, for example, NPs, small lipid exosomes, or microparticles in biomolecular diagnostics and screening, and can also utilize CARS signals from biologically relevant media other than water. PMID:26819085

  11. Thermometry for turbulent flames by coherent anti-Stokes Raman spectroscopy with simultaneous referencing to the modeless excitation profile.

    PubMed

    van Veen, Eric H; Roekaerts, Dirk

    2005-11-10

    An optimal system for temperature measurements by coherent anti-Stokes Raman spectroscopy (CARS) in turbulent flames and flows is presented. In addition to a single-mode pump laser and a modeless dye laser, an echelle spectrometer with a cross disperser is used. This system permits simultaneous measurement of the N2 CARS spectrum and the broadband dye laser profile. A procedure is developed to use software to transform this profile into the excitation profile by which the spectrum is referenced. Simultaneous shot-to-shot referencing is compared to sequential averaged referencing for data obtained in flat flames and in room air. At flame temperatures, the resultant 1.5% imprecision is limited by flame fluctuations, indicating that the system may have a single-shot imprecision below 1%. At room temperature, the 3.8% single-shot imprecision is of the same order as the best values reported for dual-broadband pure-rotational CARS. Using the unique shot-to-shot excitation profiles, simultaneous referencing eliminates systematic errors. At 2000 and 300 K, the 95% confidence intervals are estimated to be +/- 20 and +/- 10 K, respectively. PMID:16294976

  12. Simultaneous temperature and exhaust-gas recirculation-measurements in a homogeneous charge-compression ignition engine by use of pure rotational coherent anti-Stokes Raman spectroscopy.

    PubMed

    Weikl, Markus C; Beyrau, Frank; Leipertz, Alfred

    2006-05-20

    Pure rotational coherent anti-Stokes Raman spectroscopy was used for the simultaneous determination of temperature and exhaust-gas recirculation in a homogeneous charge-compression ignition engine. Measurements were performed in a production-line four-cylinder gasoline engine operated with standard gasoline fuel through small optical line-of-sight accesses. The homogenization process of fresh intake air with recirculated exhaust gas was observed during the compression stroke, and the effect of charge temperature on combustion timing is shown. Single-pulse coherent anti-Stokes Raman spectroscopy spectra could not only be taken in the compression stroke but also during the gas-exchange cycle and after combustion. Consequently, the used method has been shown to be suitable for the investigation of two of the key parameters for self-ignition, namely temperature and charge composition. PMID:16708111

  13. Study of a nitriding plasma using coherent anti-Stokes Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Pealat, M.; Lefebvre, M.

    1987-01-01

    The rotational and vibrational distribution of the first levels of excitation of N2 molecular system were measured using Raman diffusion in the discharge of a nitriding plasma. The nitrided specimens were analyzed using metallography and X-ray diffraction.

  14. Direct measurement of S-branch N2-H2 Raman linewidths using time-resolved pure rotational coherent anti-Stokes Raman spectroscopy.

    PubMed

    Bohlin, A; Nordström, E; Patterson, B D; Bengtsson, P-E; Kliewer, C J

    2012-08-21

    S-branch N(2)-H(2) Raman linewidths have been measured in the temperature region 294-1466 K using time-resolved dual-broadband picosecond pure rotational coherent anti-Stokes Raman spectroscopy (RCARS). Data are extracted by mapping the dephasing rates of the CARS signal temporal decay. The J-dependent coherence decays are detected in the time domain by following the individual spectral lines as a function of probe delay. The linewidth data set was employed in spectral fits of N(2) RCARS spectra recorded in binary mixtures of N(2) and H(2) at calibrated temperature conditions up to 661 K using a standard nanosecond RCARS setup. In this region, the set shows a deviation of less than 2% in comparison with thermocouples. The results provide useful knowledge for the applicability of N(2) CARS thermometry on the fuel-side of H(2) diffusion flames. PMID:22920115

  15. Femtosecond pulse laser notch shaping via fiber Bragg grating for the excitation source on the coherent anti-Stokes Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Oh, Seung Ryeol; Kwon, Won Sik; Kim, Jin Hwan; Kim, Kyung-Soo; Kim, Soohyun

    2015-03-01

    Single-pulse coherently controlled nonlinear Raman spectroscopy is the simplest method among the coherent anti-Stokes Raman spectroscopy systems. In recent research, it has been proven that notch-shaped femtosecond pulse laser can be used to collect the coherent anti-Stokes Raman signals. In this study, we applied a fiber Bragg grating to the notch filtering component on the femtosecond pulse lasers. The experiment was performed incorporating a titanium sapphire femtosecond pulse laser source with a 100 mm length of 780-HP fiber which is inscribed 30 mm of Bragg grating. The fiber Bragg grating has 785 nm Bragg wavelength with 0.9 nm bandwidth. We proved that if the pulse lasers have above a certain level of positive group delay dispersion, it is sufficient to propagate in the fiber Bragg grating without any spectral distortion. After passing through the fiber Bragg grating, the pulse laser is reflected on the chirped mirror for 40 times to make the transform-limited pulse. Finally, the pulse time duration was 37 fs, average power was 50mW, and showed an adequate notch shape. Furthermore, the simulation of third order polarization signal is performed using MATLAB tools and the simulation result shows that spectral characteristic and time duration of the pulse is sufficient to use as an excitation source for single-pulse coherent anti-Stokes Raman spectroscopy. In conclusion, the proposed method is more simple and cost-effective than the methods of previous research which use grating pairs and resonant photonic crystal slab.

  16. Rotational coherent anti-stokes Raman spectroscopy measurements in a rotating cavity with axial throughflow of cooling air: oxygen concentration measurements.

    PubMed

    Black, J D; Long, C A

    1992-07-20

    In a rotating cavity rig, which models cooling air flow in the spaces between disks of a gas turbine compressor, the buildup of oxygen concentration after the cooling gas was changed from nitrogen to air was monitored using rotational coherent anti-Stokes Raman spectroscopy (CARS). From this information an estimate of the fraction of the throughflow entering the rotating cavity was obtained. This demonstrates that rotational CARS can be applied as a nonintrusive concentration-measurement technique in a rotating engineering test rig. PMID:20725415

  17. Nonequilibrium vibrational excitation of H{sub 2} in radiofrequency discharges: A theoretical approach based on coherent anti-Stokes Raman spectroscopy measurements

    SciTech Connect

    Hassouni, K.; Lombardi, G.; Gicquel, A.; Capitelli, M.; Shakhatov, V.A.; De Pascale, O.

    2005-07-15

    Vibrational and rotational experimental temperatures of molecular hydrogen obtained by coherent anti-Stokes Raman spectroscopy in radiofrequency inductive plasmas have been analyzed and interpreted in terms of vibration, electron, dissociation-recombination, and attachment kinetics by using a sophisticated kinetic model recently developed. The analysis clarifies the role of atomic hydrogen in affecting the vibrational content of the molecules. Theoretical plasma composition and population and electron energy distributions are presented as a function of the recombination coefficient {gamma}{sub H} of atomic hydrogen on the surfaces. The agreement between theoretical and experimental results is achieved for recombination coefficients consistent with those found in the literature.

  18. Nonequilibrium vibrational excitation of H2 in radiofrequency discharges: A theoretical approach based on coherent anti-Stokes Raman spectroscopy measurements

    NASA Astrophysics Data System (ADS)

    Hassouni, K.; Lombardi, G.; Gicquel, A.; Capitelli, M.; Shakhatov, V. A.; De Pascale, O.

    2005-07-01

    Vibrational and rotational experimental temperatures of molecular hydrogen obtained by coherent anti-Stokes Raman spectroscopy in radiofrequency inductive plasmas have been analyzed and interpreted in terms of vibration, electron, dissociation-recombination, and attachment kinetics by using a sophisticated kinetic model recently developed. The analysis clarifies the role of atomic hydrogen in affecting the vibrational content of the molecules. Theoretical plasma composition and population and electron energy distributions are presented as a function of the recombination coefficient γH of atomic hydrogen on the surfaces. The agreement between theoretical and experimental results is achieved for recombination coefficients consistent with those found in the literature.

  19. Validation of a rotational coherent anti-Stokes Raman spectroscopy model for carbon dioxide using high-resolution detection in the temperature range 294-1143 K

    NASA Astrophysics Data System (ADS)

    Vestin, Fredrik; Nilsson, Kristin; Bengtsson, Per-Erik

    2008-04-01

    Experiments were performed in the temperature range of 294-1143 K in pure CO2 using high-resolution rotational coherent anti-Stokes Raman spectroscopy (CARS), in the dual-broadband approach. Experimental single-shot spectra were recorded with high spectral resolution using a single-mode Nd:YAG laser and a relay imaging lens system on the exit of a 1 m spectrometer. A theoretical rotational CARS model for CO2 was developed for evaluation of the experimental spectra. The evaluated mean temperatures of the recorded single-shot dual-broadband rotational coherent anti-Stokes Raman spectroscopy (DB-RCARS) spectra using this model showed good agreement with thermocouple temperatures, and the relative standard deviation of evaluated single-shot temperatures was generally 2-3%. Simultaneous thermometry and relative CO2/N2-concentration measurements were demonstrated in the product gas of premixed laminar CO/air flames at atmospheric pressure. Although the model proved to be accurate for thermometry up to 1143 K, limitations were observed at flame temperatures where temperatures were overestimated and relative CO2/N2 concentrations were underestimated. Potential sources for these discrepancies are discussed.

  20. Communication: two-dimensional gas-phase coherent anti-Stokes Raman spectroscopy (2D-CARS): simultaneous planar imaging and multiplex spectroscopy in a single laser shot.

    PubMed

    Bohlin, Alexis; Kliewer, Christopher J

    2013-06-14

    Coherent anti-Stokes Raman spectroscopy (CARS) has been widely used as a powerful tool for chemical sensing, molecular dynamics measurements, and rovibrational spectroscopy since its development over 30 years ago, finding use in fields of study as diverse as combustion diagnostics, cell biology, plasma physics, and the standoff detection of explosives. The capability for acquiring resolved CARS spectra in multiple spatial dimensions within a single laser shot has been a long-standing goal for the study of dynamical processes, but has proven elusive because of both phase-matching and detection considerations. Here, by combining new phase matching and detection schemes with the high efficiency of femtosecond excitation of Raman coherences, we introduce a technique for single-shot two-dimensional (2D) spatial measurements of gas phase CARS spectra. We demonstrate a spectrometer enabling both 2D plane imaging and spectroscopy simultaneously, and present the instantaneous measurement of 15,000 spatially correlated rotational CARS spectra in N2 and air over a 2D field of 40 mm(2). PMID:23781772

  1. Communication: Two-dimensional gas-phase coherent anti-Stokes Raman spectroscopy (2D-CARS): Simultaneous planar imaging and multiplex spectroscopy in a single laser shot

    NASA Astrophysics Data System (ADS)

    Bohlin, Alexis; Kliewer, Christopher J.

    2013-06-01

    Coherent anti-Stokes Raman spectroscopy (CARS) has been widely used as a powerful tool for chemical sensing, molecular dynamics measurements, and rovibrational spectroscopy since its development over 30 years ago, finding use in fields of study as diverse as combustion diagnostics, cell biology, plasma physics, and the standoff detection of explosives. The capability for acquiring resolved CARS spectra in multiple spatial dimensions within a single laser shot has been a long-standing goal for the study of dynamical processes, but has proven elusive because of both phase-matching and detection considerations. Here, by combining new phase matching and detection schemes with the high efficiency of femtosecond excitation of Raman coherences, we introduce a technique for single-shot two-dimensional (2D) spatial measurements of gas phase CARS spectra. We demonstrate a spectrometer enabling both 2D plane imaging and spectroscopy simultaneously, and present the instantaneous measurement of 15 000 spatially correlated rotational CARS spectra in N2 and air over a 2D field of 40 mm2.

  2. Communication: Two-dimensional gas-phase coherent anti-Stokes Raman spectroscopy (2D-CARS): Simultaneous planar imaging and multiplex spectroscopy in a single laser shot

    SciTech Connect

    Bohlin, Alexis; Kliewer, Christopher J.

    2013-01-01

    Coherent anti-Stokes Raman spectroscopy (CARS) has been widely used as a powerful tool for chemical sensing, molecular dynamics measurements, and rovibrational spectroscopy since its development over 30 years ago, finding use in fields of study as diverse as combustion diagnostics, cell biology, plasma physics, and the standoff detection of explosives. The capability for acquiring resolved CARS spectra in multiple spatial dimensions within a single laser shot has been a long-standing goal for the study of dynamical processes, but has proven elusive because of both phase-matching and detection considerations. Here, by combining new phase matching and detection schemes with the high efficiency of femtosecond excitation of Raman coherences, we introduce a technique for single-shot two-dimensional (2D) spatial measurements of gas phase CARS spectra. We demonstrate a spectrometer enabling both 2D plane imaging and spectroscopy simultaneously, and present the instantaneous measurement of 15, 000 spatially correlated rotational CARS spectra in N2 and air over a 2D field of 40 mm2.

  3. A shock pressure induced phase transition from liquid to solid of cyclohexane using time-resolved coherent anti-Stokes Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Oguchi, Shiro; Sato, Akira; Kondo, Ken-Ichi; Nakamura, Kazutaka

    2007-06-01

    The liquid-solid phase transition of cyclohexane has been studied under laser shock compression up to 3.8 GPa by using nanosecond time-resolved Coherent Anti-stokes Raman Spectroscopy (CARS) and laser shock compression. The shock wave is generated by irradiation of 10 ns pulsed laser beam on the plasma confinement target and its pressure is estimated from a particle velocity, which is measured by optically recording velocity interferometer system (ORVIS). Higher frequency shift of the Raman peaks (ring-breathing, C-C stretching, and CH2 twist modes) was observed at high pressure. At 3.8 GPa, splitting of the peak (CH2 twist mode) due to change in symmetry of surrounding molecules, which corresponds to phase transition to solid IV, was observed at delay time of 20 ns. Rapid liquid-solid phase transition has been directly observed to occur within 20 ns.

  4. Spontaneous and coherent anti-Stokes Raman spectroscopy of human gastrocnemius muscle biopsies in CH-stretching region for discrimination of peripheral artery disease

    PubMed Central

    Huang, X.; Irmak, S.; Lu, Y. F.; Pipinos, I.; Casale, G.; Subbiah, J.

    2015-01-01

    Peripheral Artery Disease (PAD) is a common manifestation of atherosclerosis, characterized by lower leg ischemia and myopathy in association with leg dysfunction. In the present study, Spontaneous and coherent anti-Stokes Raman scattering (CARS) spectroscopic techniques in CH-stretching spectral region were evaluated for discriminating healthy and diseased tissues of human gastrocnemius biopsies of control and PAD patients. Since Raman signatures of the tissues in the fingerprint region are highly complex and CH containing moieties are dense, CH-stretching limited spectral range was used to classify the diseased tissues. A total of 181 Raman spectra from 9 patients and 122 CARS spectra from 12 patients were acquired. Due to the high dimensionality of the data in Raman and CARS measurements, principal component analysis (PCA) was first performed to reduce the dimensionality of the data (6 and 9 principal scores for Raman and CARS, respectively) in the CH-stretching region, followed by a discriminant function analysis (DFA) to classify the samples into different categories based on disease severity. The CH2 and CH3 vibrational signatures were observed in the Raman and CARS spectroscopy. Raman and CARS data in conjunction with PCA-DFA analysis were capable of differentiating healthy and PAD gastrocnemius with an accuracy of 85.6% and 78.7%, respectively. PMID:26309742

  5. Femtosecond time resolved coherent anti-Stokes Raman spectroscopy of H(2)-N(2) mixtures in the Dicke regime: Experiments and modeling of velocity effects.

    PubMed

    Tran, H; Chaussard, F; Le Cong, N; Lavorel, B; Faucher, O; Joubert, P

    2009-11-01

    In this paper, we present measurements and modeling of femtosecond time resolved coherent anti-Stokes Raman spectroscopy (CARS) signal in H(2)-N(2) mixtures at low densities. Three approaches have been used to model the CARS response. The first is the usual sum of Voigt profiles. In the second approach, the speed dependent Voigt profile is used. In the last approach, a model of the temporal CARS signal is developed, which takes into account the velocity changes induced by collisions and the speed dependence of the collisional parameters. The velocity changes are modeled using the Keilson and Storer memory function; the radiator speed dependences of the collisional parameters are determined from their temperature dependences. The results obtained are consistent with previous studies in the frequency domain, showing that the changes of the velocity have important effects for the H(2)/N(2) system in the Dicke narrowing density regime. PMID:19895015

  6. Femtosecond time resolved coherent anti-Stokes Raman spectroscopy of H2-N2 mixtures in the Dicke regime: Experiments and modeling of velocity effects

    NASA Astrophysics Data System (ADS)

    Tran, H.; Chaussard, F.; Le Cong, N.; Lavorel, B.; Faucher, O.; Joubert, P.

    2009-11-01

    In this paper, we present measurements and modeling of femtosecond time resolved coherent anti-Stokes Raman spectroscopy (CARS) signal in H2-N2 mixtures at low densities. Three approaches have been used to model the CARS response. The first is the usual sum of Voigt profiles. In the second approach, the speed dependent Voigt profile is used. In the last approach, a model of the temporal CARS signal is developed, which takes into account the velocity changes induced by collisions and the speed dependence of the collisional parameters. The velocity changes are modeled using the Keilson and Storer memory function; the radiator speed dependences of the collisional parameters are determined from their temperature dependences. The results obtained are consistent with previous studies in the frequency domain, showing that the changes of the velocity have important effects for the H2/N2 system in the Dicke narrowing density regime.

  7. Coherent anti-Stokes Raman spectra of oxygen atoms in flames.

    PubMed

    Teets, R E; Bechtel, J H

    1981-10-01

    Coherent anti-Stokes Raman spectroscopy (CARS) was used to detect oxygen atoms (electronic Raman scattering) and oxygen molecules (rotational Raman scattering) in both hydrogen-oxygen and methane-oxygen flames. The high spectral resolution of CARS is useful for distinguishing the oxygen-atom signals from larger nearby rotational Raman signals. Saturation of the molecular CARS signal that is due to stimulated Raman scattering was observed. This effect limits the sensitivity of the CARS method. PMID:19710736

  8. What are the intensities and line-shapes of the twenty four polarization terms in coherent anti-Stokes Raman spectroscopy?

    NASA Astrophysics Data System (ADS)

    Niu, Kai; Lee, Soo-Y.

    2015-12-01

    Coherent anti-Stokes Raman spectroscopy (CARS) is conventionally described by just one diagram/term where the three electric field interactions act on the ket side in a Feynman dual time-line diagram in a specific time order of pump, Stokes and probe pulses. In theory, however, any third-order nonlinear spectroscopy with three different electric fields interacting with a molecule can be described by forty eight diagrams/terms. They reduce to just 24 diagrams/terms if we treat the time ordering of the electric field interactions on the ket independently of those on the bra, i.e. the ket and bra wave packets evolve independently. The twenty four polarization terms can be calculated in the multidimensional, separable harmonic oscillator model to obtain the intensities and line-shapes. It is shown that in fs/ps CARS, for the two cases of off-resonance CARS in toluene and resonance CARS in rhodamine 6G, where we use a fs pump pulse, a fs Stokes pulse and a ps probe pulse, we obtain sharp vibrational lines in four of the polarization terms where the pump and Stokes pulses can create a vibrational coherence on the ground electronic state, while the spectral line-shapes of the other twenty terms are broad and featureless. The conventional CARS term with sharp vibrational lines is the dominant term, with intensity at least one order of magnitude larger than the other terms.

  9. What are the intensities and line-shapes of the twenty four polarization terms in coherent anti-Stokes Raman spectroscopy?

    SciTech Connect

    Niu, Kai; Lee, Soo-Y.

    2015-12-15

    Coherent anti-Stokes Raman spectroscopy (CARS) is conventionally described by just one diagram/term where the three electric field interactions act on the ket side in a Feynman dual time-line diagram in a specific time order of pump, Stokes and probe pulses. In theory, however, any third-order nonlinear spectroscopy with three different electric fields interacting with a molecule can be described by forty eight diagrams/terms. They reduce to just 24 diagrams/terms if we treat the time ordering of the electric field interactions on the ket independently of those on the bra, i.e. the ket and bra wave packets evolve independently. The twenty four polarization terms can be calculated in the multidimensional, separable harmonic oscillator model to obtain the intensities and line-shapes. It is shown that in fs/ps CARS, for the two cases of off-resonance CARS in toluene and resonance CARS in rhodamine 6G, where we use a fs pump pulse, a fs Stokes pulse and a ps probe pulse, we obtain sharp vibrational lines in four of the polarization terms where the pump and Stokes pulses can create a vibrational coherence on the ground electronic state, while the spectral line-shapes of the other twenty terms are broad and featureless. The conventional CARS term with sharp vibrational lines is the dominant term, with intensity at least one order of magnitude larger than the other terms.

  10. BRIEF COMMUNICATIONS: Coherent anti-Stokes Raman scattering by excited ions in a laser plasma

    NASA Astrophysics Data System (ADS)

    Gladkov, S. M.; Zheltikov, Aleksei M.; Koroteev, Nikolai I.; Rychev, M. V.; Fedotov, Andrei B.

    1989-07-01

    The coherent anti-Stokes Raman scattering (CARS) method was used in observation of excited Al II, Al III, In II and N II in an optical breakdown plasma. The feasibility of CARS spectroscopy of multiply charged ions in a laser plasma was established.

  11. Experimental demonstration of mode-selective phonon excitation of 6H-SiC by a mid-infrared laser with anti-Stokes Raman scattering spectroscopy

    SciTech Connect

    Yoshida, Kyohei; Hachiya, Kan; Okumura, Kensuke; Mishima, Kenta; Inukai, Motoharu; Torgasin, Konstantin; Omer, Mohamed; Sonobe, Taro; Zen, Heishun; Negm, Hani; Kii, Toshiteru; Masuda, Kai; Ohgaki, Hideaki

    2013-10-28

    Mode-selective phonon excitation by a mid-infrared laser (MIR-FEL) is demonstrated via anti-Stokes Raman scattering measurements of 6H-silicon carbide (SiC). Irradiation of SiC with MIR-FEL and a Nd-YAG laser at 14 K produced a peak where the Raman shift corresponds to a photon energy of 119 meV (10.4 μm). This phenomenon is induced by mode-selective phonon excitation through the irradiation of MIR-FEL, whose photon energy corresponds to the photon-absorption of a particular phonon mode.

  12. Compressive coherent anti-Stokes Raman scattering holography.

    PubMed

    Cocking, Alexander; Mehta, Nikhil; Shi, Kebin; Liu, Zhiwen

    2015-09-21

    Coherent anti-Stokes Raman scattering (CARS) holography captures both the amplitude and the phase of the anti-Stokes field generated from a sample and can thus perform single-shot, chemically selective three-dimensional imaging. We present compressive CARS holography, a numerical technique based on the concept of compressive sensing, to improve the quality of reconstructed images by leveraging sparsity in the source distribution and reducing the out-of-focus background noise. In particular, we use the two-step iterative shrinkage threshold (TwIST) algorithm with an l1 norm regularizer to iteratively retrieve images from an off axis CARS digital hologram. It is shown that the use of compressive CARS holography enhances the CARS holographic imaging technique by reducing noise and thereby effectively emulating a higher axial resolution using only a single shot hologram. PMID:26406699

  13. Cars temperature measurements and stability studies of a d. c. nitrogen discharge. Final report, September 1989-July 1991. [CARS (coherent anti-Stokes Raman spectroscopy)

    SciTech Connect

    Millard, M.

    1991-07-01

    The vibrational and rotational temperatures of a 30-Torr, normal glow N2 gas discharge have been measured using a coherent anti-Stokes Raman spectroscopy system in the folded BOXCARS configuration. The discharge was set up in slowly flowing nitrogen between two plane parallel molybdenum electrodes. Current densities of O.047 A/sq cm were used with an E/N of approximately 50 Td. The nearly wall-less discharge was stabilized using a Macor ceramic cap covering the cathode with a 9-mm circular aperture in the center. Measurements were made at spatially resolved locations within the discharge both axially and radially. Theoretical spectra were fit to experimental data in order to obtain the rotational and vibrational temperatures and the relative populations. A detailed study of the spectral line shape of the dye laser used as the probe beam in the CARS system was carried out using the optogalvanic effect in a Fe-Ne hollow-cathode lamp. The spectral line width and lineshape under differing dye pumping schemes were obtained. These measured line widths were greater than expected and showed a non-Gaussian profile for the probe laser. Stability of the nitrogen discharge was also studied in order to determine the conditions under which the discharge remains stable. Instability was noted visually, in the behavior of the CARS signal and the electrode voltage, both of which showed hysteresis. In order to make way for changes in the system in the future, a new CARS system was designed which will allow study of various gasses under differing discharge conditions.

  14. Coherent Anti-Stokes Raman Scattering Microscopy: A Biological Review

    SciTech Connect

    Rodriguez, Luis; Lockett, Stephen J.; Holtom, Gary R.

    2006-08-31

    Microscopic imaging of cells and tissues are generated by the interaction of light with either the sample itself or contrast agents that label the sample. Most contrast agents, however, alter the cell in order to introduce molecular labels, complicating live cell imaging. The interaction of light from multiple laser sources has given rise to microscopy, based on Raman scattering or vibrational resonance, which demonstrates selectivity to specific chemical bonds while cell imaging unmodified live cells. Here, we discuss the nonlinear optical technique of coherent anti-Stokes Raman scattering (CARS) microscopy, its instrumentation, and its status in live cell imaging.

  15. Time-resolved coherent anti-Stokes Raman spectroscopy (CARS) and the measurement of vibrational spectra in shock-compressed molecular materials

    SciTech Connect

    Moore, D.S.; Schmidt, S.C.

    1990-01-01

    We present the use of coherent anti-Stokes Raman scattering (CARS) in conjunction with a two-stage light-gas gun to obtain vibrational spectra of shock-compressed liquid N{sub 2}, O{sub 2}, CO, and their mixtures. The experimental spectra are compared to spectra calculated using a semiclassical model for CARS intensities to obtain vibrational frequencies, peak Raman susceptibilities, and linewidths. The derived spectroscopic parameters suggest thermal equilibrium of the vibrational populations is established in less than a few nanoseconds after shock passage. Vibrational temperatures obtained are compared to those derived from equation-of-state calculations. Shifts in the vibrational frequencies reflect the influence of increased density and temperature on the intramolecular motion. 11 refs., 5 figs.

  16. Coherent anti-Stokes Raman scattering imaging under ambient light.

    PubMed

    Zhang, Yinxin; Liao, Chien-Sheng; Hong, Weili; Huang, Kai-Chih; Yang, Huaidong; Jin, Guofan; Cheng, Ji-Xin

    2016-08-15

    We demonstrate an ambient light coherent anti-Stokes Raman scattering microscope that allows CARS imaging to be operated under environmental light for field use. The CARS signal is modulated at megahertz frequency and detected by a photodiode equipped with a lab-built resonant amplifier, then extracted through a lock-in amplifier. The filters in both the spectral domain and the frequency domain effectively blocked the room light contamination of the CARS image. In situ hyperspectral CARS imaging of tumor tissue under ambient light is demonstrated. PMID:27519113

  17. Interpreting coherent anti-Stokes Raman spectra measured with multimode Nd:YAG pump lasers

    SciTech Connect

    Farrow, R.L.; Rahn, L.A.

    1985-06-01

    We report comparisons of coherent anti-Stokes Raman spectroscopy (CARS) measurements using single-axial-and multiaxial-mode Nd:YAG lasers. Our results demonstrate the validity of a recently proposed convolution expression for unresolved CARS spectra. The results also support the use of a relative delay of several coherence lengths between pump-beam paths for reducing the effects of pump-field statistics on the CARS spectral profile.

  18. Measurement of vibrational, gas, and rotational temperatures of H2 (X1 Σg+) in radio frequency inductive discharge plasma by multiplex coherent anti-Stokes Raman scattering spectroscopy technique

    NASA Astrophysics Data System (ADS)

    Shakhatov, V. A.; De Pascale, O.; Capitelli, M.; Hassouni, K.; Lombardi, G.; Gicquel, A.

    2005-02-01

    Translational, rotational, and vibrational temperatures of H2 in radio frequency inductive discharge plasmas at pressures and power release ranges, respectively, of 0.5-8 torr and 0.5-2W/cm3 have been measured by using multiplex coherent anti-Stokes Raman scattering (CARS) spectroscopy. Computational codes have been developed to determine the rotational and vibrational temperatures and to analyze H2 CARS spectrum for nonequilibrium conditions. The results show a decrease of the vibrational temperature from 4250 to 2800 K by increasing the pressure from 0.5 to 8 torr and a corresponding increase of the rotational temperature from 525 to 750 K.

  19. Raman and coherent anti-Stokes Raman scattering microspectroscopy for biomedical applications.

    PubMed

    Krafft, Christoph; Dietzek, Benjamin; Schmitt, Michael; Popp, Jürgen

    2012-04-01

    A tutorial article is presented for the use of linear and nonlinear Raman microspectroscopies in biomedical diagnostics. Coherent anti-Stokes Raman scattering (CARS) is the most frequently applied nonlinear variant of Raman spectroscopy. The basic concepts of Raman and CARS are introduced first, and subsequent biomedical applications of Raman and CARS are described. Raman microspectroscopy is applied to both in-vivo and in-vitro tissue diagnostics, and the characterization and identification of individual mammalian cells. These applications benefit from the fact that Raman spectra provide specific information on the chemical composition and molecular structure in a label-free and nondestructive manner. Combining the chemical specificity of Raman spectroscopy with the spatial resolution of an optical microscope allows recording hyperspectral images with molecular contrast. We also elaborate on interfacing Raman spectroscopic tools with other technologies such as optical tweezing, microfluidics and fiber optic probes. Thereby, we aim at presenting a guide into one exciting branch of modern biophotonics research. PMID:22559673

  20. Vibrational mode deactivation rates for gaseous discharge-excited nitrogen(2) on selected surfaces measured with coherent anti-Stokes Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Parish, John Walter, Jr.

    2000-09-01

    The disposal rate of nitrogen molecule internal-mode energy, kv , by deactivation in the presence of various surfaces was studied at low pressure and at approximately room temperature using coherent anti-Stokes Raman spectroscopy (CARS). Deactivation is the process whereby vibrational energy is lost one quantum or a few quanta at a time rather than all at once as in quenching. Deactivation coefficients, γv, or loss probabilities, of vibrationally-excited N2(X1Σg +,v) on gold, Pyrex, Teflon and alloys of aluminum, stainless steel and titanium, were calculated from the wall deactivation rate coefficients for the hot band quantum numbers v = 1 to 4 or 5. Vibration states were populated with a 1.5 cm diameter water-cooled-in- glass positive column discharge where the residence time was estimated to be about 60 ms in the tube. The flow rate and pressure were adjusted to optimize the populations and the observed decay. Subsequently, the excited gas was presented via a source tube to a tubular reactor. For precisely controlled residence times, the excited nitrogen would communicate with the reactor interior surface. Only the gas that had been exposed to the surface was measured upon exit from the reactor by a CARS system in the 3-D BOXCARS configuration. Extensive measurements on Pyrex gave γ 1 values between 2.4 × 10-4 and 6.7 × 10-4 depending on the treatment history of the surface. The values for γ4 ranged from 2.9 × 10-4 for the AMS 4943D alloy of titanium to approximately unity for the AMS 312 stainless steel alloy. The low value for titanium can be attributed to the oxide layer. The variation of kv with v was linear or nearly linear in all cases with slopes lower in most cases than the rate of increase of the vibration-translation V-T exchange rate with v. Direct measurement of rates, in this way, detects losses due to homogeneous gas collisions as well as heterogeneous collisions with the surface. An attempt to extract the true value of γv from the data was

  1. Quantitative coherent anti-Stokes Raman scattering (CARS) microscopy.

    PubMed

    Day, James P R; Domke, Katrin F; Rago, Gianluca; Kano, Hideaki; Hamaguchi, Hiro-o; Vartiainen, Erik M; Bonn, Mischa

    2011-06-23

    The ability to observe samples qualitatively at the microscopic scale has greatly enhanced our understanding of the physical and biological world throughout the 400 year history of microscopic imaging, but there are relatively few techniques that can truly claim the ability to quantify the local concentration and composition of a sample. We review coherent anti-Stokes Raman scattering (CARS) as a quantitative, chemically specific, and label-free microscopy. We discuss the complicating influence of the nonresonant response on the CARS signal and the various experimental and mathematical approaches that can be adopted to extract quantitative information from CARS. We also review the uses to which CARS has been employed as a quantitative microscopy to solve challenges in material and biological science. PMID:21526785

  2. Coherent anti-Stokes Raman scattering microscopy of single nanodiamonds

    PubMed Central

    Pope, Iestyn; Payne, Lukas; Zoriniants, George; Thomas, Evan; Williams, Oliver; Watson, Peter; Langbein, Wolfgang; Borri, Paola

    2016-01-01

    Nanoparticles have attracted enormous attention for biomedical applications as optical labels, drug delivery vehicles, and contrast agents in vivo. In the quest for superior photostability and bio-compatibility, nanodiamonds (NDs) are considered one of the best choices due to their unique structural, chemical, mechanical, and optical properties. So far, mainly fluorescent NDs have been utilized for cell imaging. However, their use is limited by the efficiency and costs in reliably producing fluorescent defect centers with stable optical properties. Here, we show that single non-fluorescing NDs exhibit strong coherent anti-Stokes Raman scattering (CARS) at the sp3 vibrational resonance of diamond. Using correlative light and electron microscopy, the relationship between CARS signal strength and ND size is quantified. The calibrated CARS signal in turn enables the analysis of the number and size of NDs internalized in living cells in situ, which opens the exciting prospect of following complex cellular trafficking pathways quantitatively. PMID:25305746

  3. Coherent anti-Stokes Raman scattering microscopy of single nanodiamonds

    NASA Astrophysics Data System (ADS)

    Pope, Iestyn; Payne, Lukas; Zoriniants, George; Thomas, Evan; Williams, Oliver; Watson, Peter; Langbein, Wolfgang; Borri, Paola

    2014-11-01

    Nanoparticles have attracted enormous attention for biomedical applications as optical labels, drug-delivery vehicles and contrast agents in vivo. In the quest for superior photostability and biocompatibility, nanodiamonds are considered one of the best choices due to their unique structural, chemical, mechanical and optical properties. So far, mainly fluorescent nanodiamonds have been utilized for cell imaging. However, their use is limited by the efficiency and costs in reliably producing fluorescent defect centres with stable optical properties. Here, we show that single non-fluorescing nanodiamonds exhibit strong coherent anti-Stokes Raman scattering (CARS) at the sp3 vibrational resonance of diamond. Using correlative light and electron microscopy, the relationship between CARS signal strength and nanodiamond size is quantified. The calibrated CARS signal in turn enables the analysis of the number and size of nanodiamonds internalized in living cells in situ, which opens the exciting prospect of following complex cellular trafficking pathways quantitatively.

  4. Advantage of anti-Stokes Raman scattering for high-temperature measurements

    SciTech Connect

    Fujimori, Hirotaka; Kakihana, Masato; Ioku, Koji; Goto, Seishi; Yoshimura, Masahiro

    2001-08-13

    We present the results of experiments that assess the viability of anti-Stokes scattering to investigate in situ materials at high temperatures. Both anti-Stokes and Stokes Raman measurements have been performed at various high temperatures using hafnia as a test material. As compared with Stokes Raman spectra, anti-Stokes spectra were observed with lower thermal emission backgrounds in accordance with Planck's equation. The intensity ratio of anti-Stokes to Stokes scattering approaches 1 as the temperature increases at high temperatures satisfying the Boltzmann distribution law. These results clearly demonstrate the advantage and feasibility of anti-Stokes Raman scattering for the elimination of the thermal emission in comparison with Stokes scattering. {copyright} 2001 American Institute of Physics.

  5. Investigation of enhanced forward and backward anti-stokes Raman signals in lithium niobate waveguides

    SciTech Connect

    Li, Da; Hong, Pengda; Ding, Yujie J.; Liu, Zhaojun; Wang, Lei; Hua, Ping-Rang; Zhang, De-Long

    2015-07-07

    We have observed enhancements of the anti-Stokes Raman signals generated in lithium niobate waveguides in the forward and backward configurations by at least one order of magnitude under the pump power of the microwatt level. These output signals were measured using a single photon detector. The forward and backward propagating anti-Stokes signals exhibited different spectral features.

  6. Surface enhanced coherent anti-stokes Raman scattering on nanostructured gold surfaces.

    PubMed

    Steuwe, Christian; Kaminski, Clemens F; Baumberg, Jeremy J; Mahajan, Sumeet

    2011-12-14

    Coherent anti-Stokes Raman spectroscopy (CARS) is a well-known tool in multiphoton imaging and nonlinear spectroscopy. In this work we combine CARS with plasmonic surface enhancement on reproducible nanostructured surfaces. We demonstrate strong correlation between plasmon resonances and surface-enhanced CARS (SECARS) intensities on our nanostructured surfaces and show that an enhancement of ∼10(5) can be obtained over standard CARS. Furthermore, we find SECARS to be >10(3) times more sensitive than surface-enhanced Raman Spectroscopy (SERS). We also demonstrate SECARS imaging of molecular monolayers. Our work paves the way for reliable single molecule Raman spectroscopy and fast molecular imaging on plasmonic surfaces. PMID:22074256

  7. Coherent anti-Stokes Raman scattering (CARS) detection or hot atom reaction product internal energy distributions

    SciTech Connect

    Quick, C.R. Jr.; Moore, D.S.

    1983-01-01

    Coherent anti-Stokes Raman spectroscopy (CARS) is being utilized to investigate the rovibrational energy distributions produced by reactive and nonreactive collisions of translationally hot atoms with simple molecules. Translationally hot H atoms are produced by ArF laser photolysis of HBr. Using CARS we have monitored, in a state-specific and time-resolved manner, rotational excitation of HBr (v = 0), vibrational excitation of HBr and H/sub 2/, rovibrational excitation of H/sub 2/ produced by the reaction H + HBr ..-->.. H/sub 2/ + Br, and Br atom production by photolysis of HBr.

  8. Coherent anti-Stokes Raman spectroscopic measurement of air entrainment in argon plasma jets

    SciTech Connect

    Fincke, J.R.; Rodriquez, R.; Pentecost, C.G.

    1990-01-01

    The concentration and temperature of air entrained into an argon plasma jet has been measured using coherent anti-Stokes Raman spectroscopy (CARS). The flow field is characterized by a short region of well behaved laminar flow near the nozzle exit followed by an abrupt transition to turbulence. Once the transition to turbulence occurs, air is rapidly entrained into the jet core. The location of the transition region is thought to be driven by the rapid cooling of the jet and the resulting increase in Reynolds number. 8 refs., 6 figs.

  9. Coherent anti-Stokes Raman spectroscopic measurement of air entrainment in argon plasma jets

    NASA Astrophysics Data System (ADS)

    Fincke, J. R.; Rodriquez, R.; Pentecost, C. G.

    The concentration and temperature of air entrained into an argon plasma jet has been measured using coherent anti-Stokes Raman spectroscopy (CARS). The flow field is characterized by a short region of well behaved laminar flow near the nozzle exit followed by an abrupt transition to turbulence. Once the transition to turbulence occurs, air is rapidly entrained into the jet core. The location of the transition region is thought to be driven by the rapid cooling of the jet and the resulting increase in Reynolds number.

  10. Measurement of vibrational, gas, and rotational temperatures of H{sub 2} (X{sup 1} {sigma}{sub g}{sup +}) in radio frequency inductive discharge plasma by multiplex coherent anti-Stokes Raman scattering spectroscopy technique

    SciTech Connect

    Shakhatov, V.A.; De Pascale, O.; Capitelli, M.; Hassouni, K.; Lombardi, G.; Gicquel, A.

    2005-02-01

    Translational, rotational, and vibrational temperatures of H{sub 2} in radio frequency inductive discharge plasmas at pressures and power release ranges, respectively, of 0.5-8 torr and 0.5-2 W/cm{sup 3} have been measured by using multiplex coherent anti-Stokes Raman scattering (CARS) spectroscopy. Computational codes have been developed to determine the rotational and vibrational temperatures and to analyze H{sub 2} CARS spectrum for nonequilibrium conditions. The results show a decrease of the vibrational temperature from 4250 to 2800 K by increasing the pressure from 0.5 to 8 torr and a corresponding increase of the rotational temperature from 525 to 750 K.

  11. Cars (coherent anti-Stokes Raman scattering) diagnostics in reacting mixtures

    SciTech Connect

    Valentini, J.J. )

    1989-01-01

    Coherent anti-Stokes Raman scattering (CARS) is a coherent optical variant of the inelastic light scattering process known as the Raman effect. CARS spectroscopy possesses the universality of Raman spectroscopy but with greatly enhanced sensitivity. It is insensitive to background luminescence, can be configured to allow remote measurements, has excellent temporal and spatial resolution, and can provide detailed information on both the chemical composition and physical state of gas, liquid, and solid samples. Because of these desirable attributes CARS has become an important optical diagnostic method, in particular for characterizing combustion media, plasmas, and chemically reacting mixtures. This article provides a brief introduction and overview of such applications of CARS, with a particular emphasis on the last of these.

  12. Picosecond VUV anti-Stokes Raman laser pumped by a KrF laser

    NASA Astrophysics Data System (ADS)

    Takahashi, Akihiko; Maeda, Mitsuo; Muraoka, Katsunori; Akazaki, Masanori

    1989-02-01

    Generation of picosecond vacuum ultraviolet pulses by anti-Stokes stimulated Raman Scattering (ASRS) in hydrogen gas is reported. A tunable picosecond KrF excimer laser (30 ps FWHM, 12 mJ) is used as a pump source, and a series of anti-Stokes lines up to the 9th order (128.8 nm) is efficiently generated. The transient effects due to the finite decay time of the Raman medium are discussed for the present picosecond ASRS experiment.

  13. Coherent anti-Stokes Raman scattering and spontaneous Raman scattering diagnostics of nonequilibrium plasmas and flows

    NASA Astrophysics Data System (ADS)

    Lempert, Walter R.; Adamovich, Igor V.

    2014-10-01

    The paper provides an overview of the use of coherent anti-Stokes Raman scattering (CARS) and spontaneous Raman scattering for diagnostics of low-temperature nonequilibrium plasmas and nonequilibrium high-enthalpy flows. A brief review of the theoretical background of CARS, four-wave mixing and Raman scattering, as well as a discussion of experimental techniques and data reduction, are included. The experimental results reviewed include measurements of vibrational level populations, rotational/translational temperature, electric fields in a quasi-steady-state and transient molecular plasmas and afterglow, in nonequilibrium expansion flows, and behind strong shock waves. Insight into the kinetics of vibrational energy transfer, energy thermalization mechanisms and dynamics of the pulse discharge development, provided by these experiments, is discussed. Availability of short pulse duration, high peak power lasers, as well as broadband dye lasers, makes possible the use of these diagnostics at relatively low pressures, potentially with a sub-nanosecond time resolution, as well as obtaining single laser shot, high signal-to-noise spectra at higher pressures. Possibilities for the development of single-shot 2D CARS imaging and spectroscopy, using picosecond and femtosecond lasers, as well as novel phase matching and detection techniques, are discussed.

  14. Coherent anti-Stokes Raman scattering hyperspectral tissue imaging with a wavelength-swept system.

    PubMed

    Bégin, Steve; Burgoyne, Bryan; Mercier, Vincent; Villeneuve, Alain; Vallée, Réal; Côté, Daniel

    2011-01-01

    We present a wavelength-swept coherent anti-Stokes Raman scattering (WS-CARS) spectroscopy system for hyperspectral imaging in thick tissue. We use a strategy where the Raman lines are excited sequentially, circumventing the need for a spectrometer. This fibre laser system, consisting of a pump laser synchronized with a rapidly tunable programmable laser (PL), can access Raman lines over a significant fraction of the high wavenumber region (2700-2950 cm(-1)) at rates of up to 10,000 spectral points per second. To demonstrate its capabilities, we have acquired WS-CARS spectra of several samples as well as images and hyperspectral images (HSI) of thick tissue both in forward and epi-detection. This instrument should be especially useful in providing local biochemical information with surrounding context supplied by imaging. PMID:21559141

  15. Coherent anti-Stokes Raman scattering hyperspectral tissue imaging with a wavelength-swept system

    PubMed Central

    Bégin, Steve; Burgoyne, Bryan; Mercier, Vincent; Villeneuve, Alain; Vallée, Réal; Côté, Daniel

    2011-01-01

    We present a wavelength-swept coherent anti-Stokes Raman scattering (WS-CARS) spectroscopy system for hyperspectral imaging in thick tissue. We use a strategy where the Raman lines are excited sequentially, circumventing the need for a spectrometer. This fibre laser system, consisting of a pump laser synchronized with a rapidly tunable programmable laser (PL), can access Raman lines over a significant fraction of the high wavenumber region (2700–2950 cm−1) at rates of up to 10,000 spectral points per second. To demonstrate its capabilities, we have acquired WS-CARS spectra of several samples as well as images and hyperspectral images (HSI) of thick tissue both in forward and epi-detection. This instrument should be especially useful in providing local biochemical information with surrounding context supplied by imaging. PMID:21559141

  16. Nanosecond retinal structure changes in K-590 during the room-temperature bacteriorhodopsin photocycle: picosecond time-resolved coherent anti-stokes Raman spectroscopy.

    PubMed Central

    Weidlich, O; Ujj, L; Jäger, F; Atkinson, G H

    1997-01-01

    Time-resolved vibrational spectra are used to elucidate the structural changes in the retinal chromophore within the K-590 intermediate that precedes the formation of the L-550 intermediate in the room-temperature (RT) bacteriorhodopsin (BR) photocycle. Measured by picosecond time-resolved coherent anti-Stokes Raman scattering (PTR/CARS), these vibrational data are recorded within the 750 cm-1 to 1720 cm-1 spectral region and with time delays of 50-260 ns after the RT/BR photocycle is optically initiated by pulsed (< 3 ps, 1.75 nJ) excitation. Although K-590 remains structurally unchanged throughout the 50-ps to 1-ns time interval, distinct structural changes do appear over the 1-ns to 260-ns period. Specifically, comparisons of the 50-ps PTR/CARS spectra with those recorded with time delays of 1 ns to 260 ns reveal 1) three types of changes in the hydrogen-out-of-plane (HOOP) region: the appearance of a strong, new feature at 984 cm-1; intensity decreases for the bands at 957 cm-1, 952 cm-1, and 939 cm-1; and small changes intensity and/or frequency of bands at 855 cm-1 and 805 cm-1; and 2) two types of changes in the C-C stretching region: the intensity increase in the band at 1196 cm-1 and small intensity changes and/or frequency shifts for bands at 1300 cm-1 and 1362 cm-1. No changes are observed in the C = C stretching region, and no bands assignable to the Schiff base stretching mode (C = NH+) mode are found in any of the PTR/CARS spectra assignable to K-590. These PTR/CARS data are used, together with vibrational mode assignments derived from previous work, to characterize the retinal structural changes in K-590 as it evolves from its 3.5-ps formation (ps/K-590) through the nanosecond time regime (ns/K-590) that precedes the formation of L-550. The PTR/CARS data suggest that changes in the torsional modes near the C14-C15 = N bonds are directly associated with the appearance of ns/K-590, and perhaps with the KL intermediate proposed in earlier studies. These

  17. Holographic coherent anti-Stokes Raman scattering bio-imaging

    PubMed Central

    Shi, Kebin; Edwards, Perry S.; Hu, Jing; Xu, Qian; Wang, Yanming; Psaltis, Demetri; Liu, Zhiwen

    2012-01-01

    CARS holography captures both the amplitude and the phase of a complex anti-Stokes field, and can perform three-dimensional imaging by digitally focusing onto different depths inside a specimen. The application of CARS holography for bio-imaging is demonstrated. It is shown that holographic CARS imaging of sub-cellular components in live HeLa cells can be achieved. PMID:22808443

  18. Anti-Stokes generation in a continuous-wave Raman laser

    NASA Astrophysics Data System (ADS)

    Murphy, Sytil Kathleen

    The continuous-wave Raman laser system differs from other Raman systems in that it uses cavity enhancement to augment the pump laser source rather than a high-power pulsed laser source. Through interactions of the pump laser with the Raman active medium, all Raman systems can produce both red-shifted, Stokes, emission and blue-shifted, anti-Stokes, emission. Previous, continuous-wave Raman laser systems have focused on the Stokes emission. This dissertation presents theory and data on the anti-Stokes emission. Specifically, it investigates the anti-Stokes mode structure and the emitted power as a function of input pump power, detuning, pressure, and mode combination. In order to be able to compare theory to data, the existing semi-classical CW Raman laser theory is extended to include the possibility that the spatial mode of any of the three fields (pump, Stokes, or anti-Stokes) is not the fundamental spatial mode. Numerical simulations of this theory are used to understand the behavior of the CW Raman system. All the data is compared to the theory, with varying degrees of success. The pump laser used in this research is a frequency-doubled Nd:YAG at 532 nm and the Raman active medium is H2. This combination results in Stokes and anti-Stokes wavelengths of 683 nm and 435 nm, respectively. Five methods were found in this research for increasing the amount of anti-Stokes emitted: increasing the input pump power, detuning from gain line-center of the Stokes emission, increasing the reflectivity of the cavity mirrors at the anti-Stokes wavelength, switching to a higher-order spatial mode, and decreasing the H2 pressure within the Raman cavity. In general, it was found that the higher-order anti-Stokes modes did not agree with a single theoretical spatial mode. Superpositions were formed of multiple theoretical spatial modes giving intensity distribution across the profile similar to the measured profile. Three theoretical spatial mode symmetries were investigated

  19. Diagnostics of plasmas by CARS (coherent anti-Stokes Raman scattering)

    NASA Astrophysics Data System (ADS)

    Lefebvre, M.; Pealat, M.; Taran, J. P.

    Some of the most representative results of the coherent anti-Stokes Raman spectroscopy research program on discharges at ONERA are presented. A very short review or the principles or CARS and of the main instrumental characteristics is first given. The results of an analysis or a magnetic multipole-confined H2 discharge are then shown. The kinetics of rotational and vibrational state populations have been followed in the transient regime and the deactivation of the vibrational level v = 1 by the walls measured. Also, O2 in a glow discharge and in a waveguide discharge has been studied. Rotational, vibrational temperatures and the density of the 1Delta state have been monitored as functions of position, pressure, and discharge current.

  20. Coherent Anti-Stokes Raman Spectroscopic Thermometry in a Supersonic Combustor

    NASA Technical Reports Server (NTRS)

    Cutler, A. D.; Danehy, P. M.; Springer, R. R.; OByrne, S.; Capriotti, D. P.; DeLoach, R.

    2003-01-01

    An experiment has been conducted to acquire data for the validation of computational fluid dynamics codes used in the design of supersonic combustors. The flow in a supersonic combustor, consisting of a diverging duct with a single downstream-angled wail injector, is studied. Combustor entrance Mach number is 2 and enthalpy nominally corresponds to Mach 7 flight. The primary measurement technique is coherent anti-Stokes Raman spectroscopy, but surface pressures and temperatures have also been acquired. Modern design of experiment techniques have been used to maximize the quality of the data set (for the given level of effort) and to minimize systematic errors. Temperature maps are obtained at several planes in the flow for a case in which the combustor is piloted by injecting fuel upstream of the main injector and one case in which it is not piloted. Boundary conditions and uncertainties are characterized.

  1. Coherent anti-Stokes Raman scattering microscopy: overcoming technical barriers for clinical translation

    PubMed Central

    Tu, Haohua; Boppart, Stephen A.

    2015-01-01

    Clinical translation of coherent anti-Stokes Raman scattering microscopy is of great interest because of the advantages of noninvasive label-free imaging, high sensitivity, and chemical specificity. For this to happen, we have identified and review the technical barriers that must be overcome. Prior investigations have developed advanced techniques (features), each of which can be used to effectively overcome one particular technical barrier. However, the implementation of one or a small number of these advanced features in previous attempts for clinical translation has often introduced more tradeoffs than benefits. In this review, we outline a strategy that would integrate multiple advanced features to overcome all the technical barriers simultaneously, effectively reduce tradeoffs, and synergistically optimize CARS microscopy for clinical translation. The operation of the envisioned system incorporates coherent Raman micro-spectroscopy for identifying vibrational biomolecular markers of disease and single-frequency (or hyperspectral) Raman imaging of these specific biomarkers for real-time in vivo diagnostics and monitoring. An optimal scheme of clinical CARS micro-spectroscopy for thin ex vivo tissues. PMID:23674234

  2. Investigation of anti-Stokes Raman processes at phonon-polariton resonance: from Raman oscillation, frequency upconversion to Raman amplification.

    PubMed

    Ding, Yujie J

    2015-03-01

    Raman oscillation, frequency upconversion, and Raman amplification can be achieved in a second-order nonlinear medium at the phonon-polariton resonance. By beating two optical fields, a second-order nonlinear polarization is generated inside the medium. Such a polarization induces a spatially uniform nonpropagating electric field at the beat frequency, which in turn mixes with the input optical field at the lower frequency to generate or amplify the anti-Stokes optical field. Raman oscillation can be efficiently reached for the copropagating configuration. In comparison, efficient frequency upconversion and large amplifications are achievable for the counterpropagating configuration. These Raman processes can be used to effectively remove transverse-optical phonons before decaying to lower-frequency phonons, achieve laser cooling, and significantly enhance coherent anti-Stokes Raman scattering. The counterpropagating configuration offers advantages for amplifying extremely weak signals. PMID:25723418

  3. Coherent anti-Stokes Raman scattering in benzene and nitromethane shock-compressed to 10 GPa

    SciTech Connect

    Schmidt, S.C.; Moore, D.S.; Shaner, J.W.; Shampine, D.L.; Holt, W.T.

    1985-01-01

    The frequency shifts of the ring-stretching mode of shock-compressed liquid benzene and the CN stretching mode of nitromethane have been measured using coherent anti-Stokes Raman scattering. Shock pressures up to 11 GPa were achieved using a two-stage light gas gun. The frequency shifted Raman signal was generated using single pulse Nd:YAG and broadband-type lasers. 16 refs., 3 figs.

  4. Watching orientational ordering at the nanoscale with coherent anti-stokes Raman microscopy.

    PubMed

    Parekh, Sapun H; Domke, Katrin F

    2013-09-01

    Whether in lipid membranes, liquid crystals or solid-state catalysts, the orientational ordering of molecules greatly influences the overall system behaviour. However, watching molecular alignment is a huge technical challenge. This article introduces nonlinear Raman (coherent anti-Stokes Raman scattering; CARS) microscopy as a promising tool for fast, label-free 3D chemical and structural sample characterization at the nanoscale in real time. PMID:25931284

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

    PubMed

    Li, Baolei; Warren, Warren S; Fischer, Martin C

    2010-12-01

    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. PMID:21164927

  6. Gas-phase temperature measurement in the vaporizing spray of a gasoline direct-injection injector by use of pure rotational coherent anti-Stokes Raman scattering.

    PubMed

    Beyrau, Frank; Bräuer, Andreas; Seeger, Thomas; Leipertz, Alfred

    2004-02-01

    Pure rotational coherent anti-Stokes Raman spectroscopy is applied for quantitative gas-phase temperature measurements in the vaporizing spray of an automotive fuel injector. Interferences from elastically scattered stray light are greatly reduced by use of a polarization technique and spectral filtering in a double monochromator. The applicability of this technique to probing low-temperature sprays is successfully demonstrated. PMID:14759040

  7. Evaluation of turbulence induced noise in coherent anti-Stokes Raman scattering

    NASA Technical Reports Server (NTRS)

    Elliott, R. A.

    1982-01-01

    The effect of turbulence in a transonic wind tunnel on coherent anti-Stokes Raman scattering is considered. The driving pump and Stokes waves are taken to be coaxially propagating Gaussian beam waves which are focused on the Raman active medium through the turbulent boundary layer of the flow tube. The random index of refraction variations in the layer are modeled as phase perturbations of the driving waves which cause a reduction of the mean on-axis field and an increase in the mean diameter of the beams. Effective Gaussian beam parameters are developed and the radiated anti-Stokes power calculated as a function of the phase screen parameters. A significant reduction in signal strength occurs for realistic estimates of the phase screen parameter appropriate to a confined transonic flow. A method for estimating the signal degradation which could be applied to other experimental situations is presented.

  8. Raman scattering and anomalous Stokes–anti-Stokes ratio in MoTe2 atomic layers

    PubMed Central

    Goldstein, Thomas; Chen, Shao-Yu; Tong, Jiayue; Xiao, Di; Ramasubramaniam, Ashwin; Yan, Jun

    2016-01-01

    Stokes and anti-Stokes Raman scattering are performed on atomic layers of hexagonal molybdenum ditelluride (MoTe2), a prototypical transition metal dichalcogenide (TMDC) semiconductor. The data reveal all six types of zone center optical phonons, along with their corresponding Davydov splittings, which have been challenging to see in other TMDCs. We discover that the anti-Stokes Raman intensity of the low energy layer-breathing mode becomes more intense than the Stokes peak under certain experimental conditions, and find the effect to be tunable by excitation frequency and number of atomic layers. These observations are interpreted as a result of resonance effects arising from the C excitons in the vicinity of the Brillouin zone center in the photon-electron-phonon interaction process. PMID:27324297

  9. Measurement of vibrational populations in hydrogen plasma by coherent anti-Stokes Raman scattering

    NASA Astrophysics Data System (ADS)

    Pealat, M.; Taran, J. P.; Taillet, J.; Bacal, M.; Bruneteau, A. M.

    Coherent anti-Stokes Raman Scattering (CARS) has been applied to the measurement of vibrational populations in a low-pressure H2 plasma. For an electron density of 2 x 10 to the 11th/cu cm and a total pressure of 0.13 mbar, the rotational temperature is found to be 475 K. The population of vibrational states 0, 1 and 2 has a non-Boltzmann distribution.

  10. Vibrational Imaging with High Sensitivity via Epidetected Coherent Anti-Stokes Raman Scattering Microscopy

    SciTech Connect

    Volkmer, Andreas; Cheng, Ji-Xin; Sunney Xie, X.

    2001-07-09

    We demonstrate theoretically and experimentally a novel epidetection scheme for coherent anti-Stokes Raman scattering (CARS) microscopy that significantly improves the detection sensitivity. Calculations show that epidetected CARS (E-CARS) signals are present for scatterers smaller than the wavelength of light, whereas the large background signals from the surrounding bulk solvent are suppressed by destructive interference. E-CARS microscopy is capable of revealing small intracellular features that are otherwise buried by the strong water CARS signal.

  11. Macrophages interaction with pulmonary surfactant using coherent anti-Stokes Raman scattering (CARS) microscopy

    NASA Astrophysics Data System (ADS)

    Ocampo, Minette; Telesford, Dana Marie; Allen, Heather

    2012-04-01

    Alveolar pulmonary surfactant, composed mostly of phospholipids, is essential for maintenance of normal lung function. However, increased production of lung surfactant can lead to many pulmonary inflammatory disorders. Alveolar macrophages are responsible for the degradation of the surfactant and exhibit increased lipid uptake in inflamated lungs. Owing to their limited clearance capability, excessive accumulation of surfactant may impair their phagocytic function. In this study, the interaction of the macrophages with different lipid components was studied using coherent anti-Stokes Raman scattering (CARS) microscopy. CARS microscopy, a nonlinear vibrational technique which combines spectroscopy and microscopy, allows noninvasive characterization and imaging of chemical species without preparation or labeling. A monolayer of THP-1 macrophages and palmitic acid-d31 on phosphate buffer solution was transferred to a coverslip using the Langmuir-Blodgett method and then imaged using CARS by mapping the CH2 stretch signal of the lipid membrane of the macrophage and C-D stretch signal from palmitic acid-d31. Preliminary results showed CARS images of the macrophage on the solid substrate and thermal degradation of the sample due to long exposure to high laser power. A contrast image is expected to be observed by mapping the CH2 and C-D signals, which can show the lipid interaction and phagocytosis of the macrophage.

  12. Optimal coherent control of coherent anti-Stokes Raman scattering: Signal enhancement and background elimination

    NASA Astrophysics Data System (ADS)

    Gao, Fang; Shuang, Feng; Shi, Junhui; Rabitz, Herschel; Wang, Haifeng; Cheng, Ji-Xin

    2012-04-01

    The ability to enhance resonant signals and eliminate the non-resonant background is analyzed for coherent anti-Stokes Raman scattering (CARS). The analysis is done at a specific frequency as well as for broadband excitation using femtosecond pulse-shaping techniques. An appropriate objective functional is employed to balance resonant signal enhancement against non-resonant background suppression. Optimal enhancement of the signal and minimization of the background can be achieved by shaping the probe pulse alone while keeping the pump and Stokes pulses unshaped. In some cases analytical forms for the probe pulse can be found, and numerical simulations are carried out for other circumstances. It is found that a good approximate optimal solution for resonant signal enhancement in two-pulse CARS is a superposition of linear and arctangent-type phases for the pump. The well-known probe delay method is shown to be a quasi-optimal scheme for broadband background suppression. The results should provide a basis to improve the performance of CARS spectroscopy and microscopy.

  13. Revealing silent vibration modes of nanomaterials by detecting anti-Stokes hyper-Raman scattering with femtosecond laser pulses.

    PubMed

    Zeng, Jianhua; Chen, Lei; Dai, Qiaofeng; Lan, Sheng; Tie, Shaolong

    2016-01-21

    We proposed a scheme in which normal Raman scattering is coupled with hyper-Raman scattering for generating a strong anti-Stokes hyper-Raman scattering in nanomaterials by using femtosecond laser pulses. The proposal was experimentally demonstrated by using a single-layer MoS2 on a SiO2/Si substrate, a 17 nm-thick MoS2 on an Au/SiO2 substrate and a 9 nm-thick MoS2 on a SiO2-SnO2/Ag/SiO2 substrate which were confirmed to be highly efficient for second harmonic generation. A strong anti-Stokes hyper-Raman scattering was also observed in other nanomaterials possessing large second-order susceptibilities, such as silicon quantum dots self-assembled into "coffee" rings and tubular Cu-doped ZnO nanorods. In all the cases, many Raman inactive vibration modes were clearly revealed in the anti-Stokes hyper-Raman scattering. Apart from the strong anti-Stokes hyper-Raman scattering, Stokes hyper-Raman scattering with small Raman shifts was detected during the ablation process of thick MoS2 layers. It was also observed by slightly defocusing the excitation light. The detection of anti-Stokes hyper-Raman scattering may serve as a new technique for studying the Raman inactive vibration modes in nanomaterials. PMID:26690965

  14. Direct imaging of molecular symmetry by coherent anti-stokes Raman scattering.

    PubMed

    Cleff, Carsten; Gasecka, Alicja; Ferrand, Patrick; Rigneault, Hervé; Brasselet, Sophie; Duboisset, Julien

    2016-01-01

    Nonlinear optical methods, such as coherent anti-Stokes Raman scattering and stimulated Raman scattering, 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 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 information not accessible by spontaneous Raman and stimulated Raman scattering techniques. This work stands for a symmetry-resolved contrast in vibrational microscopy, with potential application in biological diagnostic. PMID:27189667

  15. Direct imaging of molecular symmetry by coherent anti-stokes Raman scattering

    NASA Astrophysics Data System (ADS)

    Cleff, Carsten; Gasecka, Alicja; Ferrand, Patrick; Rigneault, Hervé; Brasselet, Sophie; Duboisset, Julien

    2016-05-01

    Nonlinear optical methods, such as coherent anti-Stokes Raman scattering and stimulated Raman scattering, 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 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 information not accessible by spontaneous Raman and stimulated Raman scattering techniques. This work stands for a symmetry-resolved contrast in vibrational microscopy, with potential application in biological diagnostic.

  16. Direct imaging of molecular symmetry by coherent anti-stokes Raman scattering

    PubMed Central

    Cleff, Carsten; Gasecka, Alicja; Ferrand, Patrick; Rigneault, Hervé; Brasselet, Sophie; Duboisset, Julien

    2016-01-01

    Nonlinear optical methods, such as coherent anti-Stokes Raman scattering and stimulated Raman scattering, 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 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 information not accessible by spontaneous Raman and stimulated Raman scattering techniques. This work stands for a symmetry-resolved contrast in vibrational microscopy, with potential application in biological diagnostic. PMID:27189667

  17. Anti-Stokes Raman laser investigations on atomic Tl and Sn

    NASA Astrophysics Data System (ADS)

    Ludewigt, K.; Birkmann, K.; Wellegehausen, B.

    1984-03-01

    Anti-Stokes Raman laser experiments using metastable atomic Tl and Sn have been performed. The required metastable population inversion is generated by photodissociation of TlI and SnBr2 with KrF laser radiation. The Tl(Sn) system permits frequency up-conversion by 7793 cm-1 (17,163 cm-1). By optimization of system parameters, uv output energies up to 2.5 mJ (377 nm) and conversion efficiencies of more than 25% have been achieved for Tl. Further improvements and principal limitations will be discussed.

  18. Optimizing coherent anti-Stokes Raman scattering by genetic algorithm controlled pulse shaping

    NASA Astrophysics Data System (ADS)

    Yang, Wenlong; Sokolov, Alexei

    2010-10-01

    The hybrid coherent anti-Stokes Raman scattering (CARS) has been successful applied to fast chemical sensitive detections. As the development of femto-second pulse shaping techniques, it is of great interest to find the optimum pulse shapes for CARS. The optimum pulse shapes should minimize the non-resonant four wave mixing (NRFWM) background and maximize the CARS signal. A genetic algorithm (GA) is developed to make a heuristic searching for optimized pulse shapes, which give the best signal the background ratio. The GA is shown to be able to rediscover the hybrid CARS scheme and find optimized pulse shapes for customized applications by itself.

  19. Multimodal coherent anti-Stokes Raman spectroscopic imaging with a fiber optical parametric oscillator

    PubMed Central

    Zhai, Yan-Hua; Goulart, Christiane; Sharping, Jay E.; Wei, Huifeng; Chen, Su; Tong, Weijun; Slipchenko, Mikhail N.; Zhang, Delong; Cheng, Ji-Xin

    2011-01-01

    We report on multimodal coherent anti-Stokes Raman scattering (CARS) imaging with a source composed of a femtosecond fiber laser and a photonic crystal fiber (PCF)-based optical parametric oscillator (FOPO). By switching between two PCFs with different zero dispersion wavelengths, a tunable signal beam from the FOPO covering the range from 840 to 930 nm was produced. By combining the femtosecond fiber laser and the FOPO output, simultaneous CARS imaging of a myelin sheath and two-photon excitation fluorescence imaging of a labeled axons in rat spinal cord have been demonstrated at the speed of 20 μs per pixel. PMID:21677908

  20. A versatile setup using femtosecond adaptive spectroscopic techniques for coherent anti-Stokes Raman scattering

    NASA Astrophysics Data System (ADS)

    Shen, Yujie; Voronine, Dmitri V.; Sokolov, Alexei V.; Scully, Marlan O.

    2015-08-01

    We report a versatile setup based on the femtosecond adaptive spectroscopic techniques for coherent anti-Stokes Raman scattering. The setup uses a femtosecond Ti:Sapphire oscillator source and a folded 4f pulse shaper, in which the pulse shaping is carried out through conventional optical elements and does not require a spatial light modulator. Our setup is simple in alignment, and can be easily switched between the collinear single-beam and the noncollinear two-beam configurations. We demonstrate the capability for investigating both transparent and highly scattering samples by detecting transmitted and reflected signals, respectively.

  1. A versatile setup using femtosecond adaptive spectroscopic techniques for coherent anti-Stokes Raman scattering

    SciTech Connect

    Shen, Yujie; Voronine, Dmitri V.; Sokolov, Alexei V.; Scully, Marlan O.

    2015-08-15

    We report a versatile setup based on the femtosecond adaptive spectroscopic techniques for coherent anti-Stokes Raman scattering. The setup uses a femtosecond Ti:Sapphire oscillator source and a folded 4f pulse shaper, in which the pulse shaping is carried out through conventional optical elements and does not require a spatial light modulator. Our setup is simple in alignment, and can be easily switched between the collinear single-beam and the noncollinear two-beam configurations. We demonstrate the capability for investigating both transparent and highly scattering samples by detecting transmitted and reflected signals, respectively.

  2. Measurement of nitric oxide concentrations in flames by using electronic-resonance-enhanced coherent anti-Stokes Raman scattering.

    PubMed

    Kulatilaka, Waruna D; Chai, Ning; Naik, Sameer V; Laurendeau, Normand M; Lucht, Robert P; Kuehner, Joel P; Roy, Sukesh; Gord, James R

    2006-11-15

    We have measured nitric oxide (NO) concentrations in flames by using electronic-resonance-enhanced coherent anti-Stokes Raman spectroscopy (ERE-CARS). Visible pump and Stokes beams were tuned to a Q-branch vibrational Raman resonance of NO. A UV probe beam was tuned into resonance with specific rotational transitions in the (v"=1,v'=0) vibrational band in the A(2)Sigma(+)-X(2)Pi electronic transition, thus providing a substantial electronic-resonance enhancement of the resulting CARS signal. NO concentrations were measured at levels down to 50 parts in 10(6) in H(2)/air flames at atmospheric pressure. NO was also detected in heavily sooting C(2)H(2)/air flames at atmospheric pressure with minimal background interference. PMID:17072422

  3. Spontaneous Anti-Stokes Raman Probe for Gas Temperature Measurements in Industrial Furnaces

    NASA Astrophysics Data System (ADS)

    Zikratov, George; Yueh, Fang-Yu; Singh, Jagdish P.; Norton, O. Perry; Kumar, R. Arun; Cook, Robert L.

    1999-03-01

    A compact, pulsed Nd:YAG laser-based instrument has been built to measure in situ absolute gas temperatures in large industrial furnaces by use of spontaneous anti-Stokes Raman scattering. The backscattering configuration was used to simplify the optics alignment and increase signal-to-noise ratios. Gated signal detection significantly reduced the background emission that is found in combustion environments. The anti-Stokes instead of the Stokes component was used to eliminate contributions to spectra from cold atmospheric nitrogen. The system was evaluated in a methane air flame and in a bench-top oven, and the technique was found to be a reliable tool for nonintrusive absolute temperature measurements with relatively clean gas streams. A water-cooled insertion probe was integrated with the Raman system for measurement of the temperature profiles inside an industrial furnace. Gas temperatures near 1500 1800 K at atmospheric pressure in an industrial furnace were inferred by fitting calculated profiles to experimental spectra with a standard deviation of less than 1% for averaging times of 200 s. The temperatures inferred from Raman spectra are in good agreement with data recorded with a thermocouple probe.

  4. Coherent anti-Stokes Raman scattering study of the dynamics of a multipolar plasma generator

    NASA Astrophysics Data System (ADS)

    Lefebvre, M.; Péalat, M.; Taran, J.-P.; Bacal, M.; Berlemont, P.; Skinner, D. A.; Bretagne, J.; Hutcheon, R. J.

    1992-03-01

    A Coherent Anti-Stokes Raman Spectroscopy (CARS) study of the hydrogen plasma generated by a discharge with magnetic multipolar confinement has been conducted at pressures in the range 0.5-5 Pa. The steady-state radial distribution of the rovibrational populations has been measured. The vibrational temperature is always uniformly distributed and so is the rotational temperature at the lower pressures, while a strong gradient is seen at 5 Pa for the rotation. Time-resolved measurements with the discharge operated in a square-pulse mode give additional insight into the dynamics of the discharge. Some results are compared with the predictions of two computer models of the plasma kinetics. We observe H{2} vibrational excitation by the Joule-heated filament alone (in the absence of the discharge) and show it to be caused primarily by the confined discharge between the filament and its cold positive copper connector. Another interpretation of the presence of vibrationally excited H{2} by recombinative desorption (Hall R.I. et al., Phys. Rev. Lett. 60 (1988) 337) is not comforted by our results, within instrumental sensitivity. The densities of the first rotational levels that the ortho and para forms of H{2} have different electron collisional cross-sections. Under pulsed excitation, the vibrational temperature rises on a time scale of 1-2 ms in agreement with numerical predictions. At switch-off, we show by matching the experimental and theoretical decays that vibrational state v=1 survives 16± 5 wall collisions; meanwhile, the rotation cools very rapidly, probably because of superelastic electronic collisions.

  5. Picosecond spectral coherent anti-Stokes Raman scattering imaging with principal component analysis of meibomian glands

    NASA Astrophysics Data System (ADS)

    Lin, Chia-Yu; Suhalim, Jeffrey L.; Nien, Chyong Ly; Miljković, Miloš D.; Diem, Max; Jester, James V.; Potma, Eric. O.

    2011-02-01

    The lipid distribution in the mouse meibomian gland was examined with picosecond spectral anti-Stokes Raman scattering (CARS) imaging. Spectral CARS data sets were generated by imaging specific localized regions of the gland within tissue sections at consecutive Raman shifts in the CH2 stretching vibrational range. Spectral differences between the location specific CARS spectra obtained in the lipid-rich regions of the acinus and the central duct were observed, which were confirmed with a Raman microspectroscopic analysis, and attributed to meibum lipid modifications within the gland. A principal component analysis of the spectral data set reveals changes in the CARS spectrum when transitioning from the acini to the central duct. These results demonstrate the utility of picosecond spectral CARS imaging combined with multivariate analysis for assessing differences in the distribution and composition of lipids in tissues.

  6. Heterodyne coherent anti-Stokes Raman scattering by the phase control of its intrinsic background

    SciTech Connect

    Wang Xi; Wang Kai; Welch, George R.; Sokolov, Alexei V.

    2011-08-15

    We demonstrate the use of femtosecond laser pulse shaping for precise control of the interference between the coherent anti-Stokes Raman scattering (CARS) signal and the coherent nonresonant background generated within the same sample volume. Our technique is similar to heterodyne detection with the coherent background playing the role of the local oscillator field. In our experiment, we first apply two ultrashort (near-transform-limited) femtosecond pump and Stokes laser pulses to excite coherent molecular oscillations within a sample. After a short and controllable delay, we then apply a laser pulse that scatters off of these oscillations to produce the CARS signal. By making fine adjustments to the probe field spectral profile, we vary the relative phase between the Raman-resonant signal and the nonresonant background, and we observe a varying spectral interference pattern. These controlled variations of the measured pattern reveal the phase information within the Raman spectrum.

  7. Heterodyne coherent anti-Stokes Raman scattering by the phase control of its intrinsic background

    NASA Astrophysics Data System (ADS)

    Wang, Xi; Wang, Kai; Welch, George R.; Sokolov, Alexei V.

    2011-08-01

    We demonstrate the use of femtosecond laser pulse shaping for precise control of the interference between the coherent anti-Stokes Raman scattering (CARS) signal and the coherent nonresonant background generated within the same sample volume. Our technique is similar to heterodyne detection with the coherent background playing the role of the local oscillator field. In our experiment, we first apply two ultrashort (near-transform-limited) femtosecond pump and Stokes laser pulses to excite coherent molecular oscillations within a sample. After a short and controllable delay, we then apply a laser pulse that scatters off of these oscillations to produce the CARS signal. By making fine adjustments to the probe field spectral profile, we vary the relative phase between the Raman-resonant signal and the nonresonant background, and we observe a varying spectral interference pattern. These controlled variations of the measured pattern reveal the phase information within the Raman spectrum.

  8. Chemical imaging and microspectroscopy with spectral focusing coherent anti-Stokes Raman scattering.

    PubMed

    Chen, Bi-Chang; Sung, Jiha; Wu, Xiaoxi; Lim, Sang-Hyun

    2011-02-01

    We demonstrate two different coherent anti-Stokes Raman scattering (CARS) microscopy and microspectroscopy methods based on the spectral focusing mechanism. The first method uses strongly chirped broadband pulses from a single Ti:sapphire laser and generates CARS signals at the fingerprint region. Fast modulation of the time delay between the pump and Stokes laser pulses coupled with lock-in signal detection significantly reduces the nonresonant background and produces Raman-like CARS signals with a spectral resolution of 20 cm(-1). The second method generates CARS signals in the CH (carbon-hydrogen) stretching region with IR supercontinuum pulses from a photonic crystal fiber. The spectral resolution of 30 cm(-1) is achieved. Maximum entropy method is used to retrieve a Raman-equivalent CARS spectrum from lipid membranes. Chemical imaging and microspectroscopy are demonstrated with various samples. PMID:21361675

  9. Broadband coherent anti-Stokes Raman scattering light generation in BBO crystal by using two crossing femtosecond laser pulses.

    PubMed

    Liu, Jun; Zhang, Jun; Kobayashi, Takayoshi

    2008-07-01

    As broad as 12000 cm(-1) coherent anti-Stokes Raman scattering (CARS) light from ultraviolet to infrared was generated in a BBO crystal by using two crossing femtosecond laser pulses with 30% conversion efficiency. More than fifteenth-order anti-Stokes and second-order Stokes Raman sidebands were observed with nice Gaussian spatial mode. The effect of the crossing angle between two input beams on the spectrum and emitting angle of the Raman sidebands was studied in detail. Calculation shows that the phase-matching condition determines the frequencies and angles of the sidebands. PMID:18594676

  10. Label-free imaging of adipogenesis by coherent anti-stokes Raman scattering microscopy.

    PubMed

    Isomäki, Antti; Sillat, Tarvo; Ainola, Mari; Liljeström, Mikko; Konttinen, Yrjö T; Hukkanen, Mika

    2014-01-01

    Label-free imaging technologies to monitor the events associated with early, intermediate and late adipogenic differentiation in multipotent mesenchymal stromal cells (MSCs) offer an attractive and convenient alternative to conventional fixative based lipid dyes such as Oil Red O and Sudan Red, fluorescent labels such as LipidTOX, and more indirect methods such as qRT-PCR analyses of specific adipocyte differentiation markers such as peroxisome PPARγ and LPL. Coherent anti-Stokes Raman scattering (CARS) microscopy of live cells is a sensitive and fast imaging method enabling evaluation of the adipogenic differentiation with chemical specificity. CARS microscopy is based on imaging structures of interest by displaying the characteristic intrinsic vibrational contrast of chemical bonds. The method is nontoxic, non-destructive, and minimally invasive, thus presenting a promising method for longitudinal analyses of live cells and tissues. CARS provides a coherently emitted signal that is much stronger than the spontaneous Raman scattering. The anti-Stokes signal is blue shifted from the incident wavelength, thus reducing the non-vibrational background present in most biological materials. In this chapter, we aim to provide a detailed approach on how to induce adipogenic differentiation in MSC cultures, and present our methods related to label-free CARS imaging of the events associated with the adipogenesis. PMID:24706284

  11. Revealing silent vibration modes of nanomaterials by detecting anti-Stokes hyper-Raman scattering with femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Zeng, Jianhua; Chen, Lei; Dai, Qiaofeng; Lan, Sheng; Tie, Shaolong

    2016-01-01

    We proposed a scheme in which normal Raman scattering is coupled with hyper-Raman scattering for generating a strong anti-Stokes hyper-Raman scattering in nanomaterials by using femtosecond laser pulses. The proposal was experimentally demonstrated by using a single-layer MoS2 on a SiO2/Si substrate, a 17 nm-thick MoS2 on an Au/SiO2 substrate and a 9 nm-thick MoS2 on a SiO2-SnO2/Ag/SiO2 substrate which were confirmed to be highly efficient for second harmonic generation. A strong anti-Stokes hyper-Raman scattering was also observed in other nanomaterials possessing large second-order susceptibilities, such as silicon quantum dots self-assembled into ``coffee'' rings and tubular Cu-doped ZnO nanorods. In all the cases, many Raman inactive vibration modes were clearly revealed in the anti-Stokes hyper-Raman scattering. Apart from the strong anti-Stokes hyper-Raman scattering, Stokes hyper-Raman scattering with small Raman shifts was detected during the ablation process of thick MoS2 layers. It was also observed by slightly defocusing the excitation light. The detection of anti-Stokes hyper-Raman scattering may serve as a new technique for studying the Raman inactive vibration modes in nanomaterials.We proposed a scheme in which normal Raman scattering is coupled with hyper-Raman scattering for generating a strong anti-Stokes hyper-Raman scattering in nanomaterials by using femtosecond laser pulses. The proposal was experimentally demonstrated by using a single-layer MoS2 on a SiO2/Si substrate, a 17 nm-thick MoS2 on an Au/SiO2 substrate and a 9 nm-thick MoS2 on a SiO2-SnO2/Ag/SiO2 substrate which were confirmed to be highly efficient for second harmonic generation. A strong anti-Stokes hyper-Raman scattering was also observed in other nanomaterials possessing large second-order susceptibilities, such as silicon quantum dots self-assembled into ``coffee'' rings and tubular Cu-doped ZnO nanorods. In all the cases, many Raman inactive vibration modes were clearly

  12. Glucose concentration measured by the hybrid coherent anti-Stokes Raman-scattering technique

    SciTech Connect

    Wang Xi; Zhang Aihua; Zhi Miaochan; Sokolov, Alexei V.; Welch, George R.

    2010-01-15

    We investigate the possibility of using a hybrid coherent anti-Stokes Raman scattering technique for noninvasive monitoring of blood glucose levels. Our technique combines instantaneous coherent excitation of several characteristic molecular vibrations with subsequent probing of these vibrations by an optimally shaped, time-delayed, narrowband laser pulse. This pulse configuration mitigates the nonresonant four-wave mixing background while maximizing the Raman-resonant signal and allows rapid and highly specific detection even in the presence of multiple scattering. Under certain conditions we find that the measured signal is linearly proportional to the glucose concentration due to optical interference with the residual background light, which allows reliable detection of spectral signatures down to medically relevant glucose levels.

  13. Glucose concentration measured by the hybrid coherent anti-Stokes Raman-scattering technique

    NASA Astrophysics Data System (ADS)

    Wang, Xi; Zhang, Aihua; Zhi, Miaochan; Sokolov, Alexei V.; Welch, George R.

    2010-01-01

    We investigate the possibility of using a hybrid coherent anti-Stokes Raman scattering technique for noninvasive monitoring of blood glucose levels. Our technique combines instantaneous coherent excitation of several characteristic molecular vibrations with subsequent probing of these vibrations by an optimally shaped, time-delayed, narrowband laser pulse. This pulse configuration mitigates the nonresonant four-wave mixing background while maximizing the Raman-resonant signal and allows rapid and highly specific detection even in the presence of multiple scattering. Under certain conditions we find that the measured signal is linearly proportional to the glucose concentration due to optical interference with the residual background light, which allows reliable detection of spectral signatures down to medically relevant glucose levels.

  14. Surface-enhanced coherent anti-Stokes Raman imaging of lipids.

    PubMed

    Fast, Alexander; Kenison, John P; Syme, Christopher D; Potma, Eric O

    2016-08-01

    This work describes in detail a wide-field surface-enhanced coherent anti-Stokes Raman scattering (CARS) microscope, which enables enhanced detection of sample structures in close proximity (∼100  nm) of the substrate interface. Unlike conventional CARS microscopy, where the sample is illuminated with freely propagating light, the current implementation uses evanescent fields to drive Raman coherences across the entire object plane. By coupling the pump and Stokes excitation beams to the surface plasmon-polariton mode at the interface of a 30 nm thick gold film, we obtained strong CARS signals from cholesteryl oleate droplets adhered to the surface. The surface-enhanced CARS imaging system visualizes lipid structures with vibrational selectivity using illumination doses per unit area that are more than four orders of magnitude lower than in point-scanning CARS microscopy. PMID:27505381

  15. Supercontinuum generation for coherent anti-Stokes Raman scattering microscopy with photonic crystal fibers.

    PubMed

    Klarskov, Pernille; Isomäki, Antti; Hansen, Kim P; Andersen, Peter E

    2011-12-19

    Photonic crystal fiber (PCF) designs with two zero-dispersion wavelengths (ZDWs) are experimentally investigated in order to suggest a novel PCF for coherent anti-Stokes Raman scattering (CARS) microscopy. From our investigation, we select the optimum PCF design and demonstrate a tailored spectrum with power concentrated around the relevant wavelengths for lipid imaging (648 nm and 1027 nm). This new PCF is characterized by varying the fiber length, the average power, and the pulse width of the fs pump pulses. It was found that the selected PCF design gave a significantly improved spectral distribution compared to an existing PCF for CARS microscopy. Furthermore, the PCF is designed in a twofold symmetric structure allowing for polarization maintaining propagation. Finally, the pulse propagation is investigated numerically showing good agreement with the measured spectrum. From the numerical analysis, the nonlinear effects responsible for the spectral broadening are explained to be soliton fission processes, dispersive waves, and stimulated Raman scattering. PMID:22274252

  16. Effects of tissue fixation on coherent anti-Stokes Raman scattering images of brain

    NASA Astrophysics Data System (ADS)

    Galli, Roberta; Uckermann, Ortrud; Koch, Edmund; Schackert, Gabriele; Kirsch, Matthias; Steiner, Gerald

    2014-07-01

    Coherent anti-Stokes Raman scattering (CARS) microscopy is an emerging multiphoton technique for the label-free histopathology of the central nervous system, by imaging the lipid content within the tissue. In order to apply the technique on standard histology sections, it is important to know the effects of tissue fixation on the CARS image. Here, we report the effects of two common fixation methods, namely with formalin and methanol-acetone, on mouse brain and human glioblastoma tissue. The variations induced by fixation on the CARS contrast and intensity were compared and interpreted using Raman microspectroscopy. The results show that, whenever unfixed cryosections cannot be used, fixation with formalin constitutes an alternative which does not deteriorate substantially the contrast generated by the different brain structures in the CARS image. Fixation with methanol-acetone strongly modifies the tissue lipid content and is therefore incompatible with the CARS imaging.

  17. LD-side-pumped Nd:YAG/BaWO4 intracavity Raman laser for anti-Stokes generation

    NASA Astrophysics Data System (ADS)

    Wang, Cong; Cong, Zhenhua; Qin, Zengguang; Zhang, Xingyu; Wei, Wei; Wang, Weitao; Zhang, Yuangeng; Zhang, Huaijin; Yu, Haohai

    2014-07-01

    A diode-side-pumped actively Q-switched Nd:YAG/BaWO4 intracavity anti-Stokes Raman laser is demonstrated for the first time. The oscillation directions of the fundamental and the Stokes beams are separated at a phase-matching angle by introducing an additional coupled Raman cavity in the fundamental resonator. The highest 968 nm anti-Stokes output power of 0.94 mW is obtained with a 170 W 808 nm pumping power and a 7.5 kHz pulse repetition frequency. Meanwhile, the Stokes power obtained is 4.2 W.

  18. Detection of chemical interfaces in coherent anti-Stokes Raman scattering microscopy: Dk-CARS. I. Axial interfaces.

    PubMed

    Gachet, David; Rigneault, Hervé

    2011-12-01

    We develop a full vectorial theoretical investigation of the chemical interface detection in conventional coherent anti-Stokes Raman scattering (CARS) microscopy. In Part I, we focus on the detection of axial interfaces (i.e., parallel to the optical axis) following a recent experimental demonstration of the concept [Phys. Rev. Lett. 104, 213905 (2010)]. By revisiting the Young's double slit experiment, we show that background-free microscopy and spectroscopy is achievable through the angular analysis of the CARS far-field radiation pattern. This differential CARS in k space (Dk-CARS) technique is interesting for fast detection of interfaces between molecularly different media. It may be adapted to other coherent and resonant scattering processes. PMID:22193265

  19. Detection of chemical interfaces in coherent anti-Stokes Raman scattering microscopy: D-CARS. II. Arbitrary interfaces.

    PubMed

    Gachet, David; Rigneault, Hervé

    2011-12-01

    We address the general problem of detecting chemical interfaces arbitrarily oriented in space in coherent anti-Stokes Raman scattering (CARS) microscopy. Such a task is accomplished by using a beam reversal scheme, as recently demonstrated experimentally [J. Biomed. Opt. 16, 086006 (2011)]. We develop a full vectorial theoretical analysis of the situation and show that transverse chemical interfaces are readily highlighted without special care in the CARS signal detection. In addition, a finer analysis reveals that adequate angular analysis of the CARS far-field radiation pattern enables the detection of axial interfaces. Background-free CARS microscopy and spectroscopy are thus achievable through the combined application of excitation beam reversal and angular analysis of the CARS far-field radiation pattern. This differential CARS (D-CARS) technique is relevant for fast detection of interfaces between molecularly different media. PMID:22193266

  20. Theory of femtosecond coherent anti-Stokes Raman backscattering enhanced by quantum coherence for standoff detection of bacterial spores

    NASA Astrophysics Data System (ADS)

    Ooi, C. H. Raymond; Beadie, Guy; Kattawar, George W.; Reintjes, John F.; Rostovtsev, Yuri; Zubairy, M. Suhail; Scully, Marlan O.

    2005-08-01

    Backscattered signal of coherent anti-Stokes Raman spectroscopy can be an extremely useful tool for remote identification of airborne particles, provided the signal is sufficiently large. We formulate a semiclassical theory of nonlinear scattering to estimate the number of detectable photons from a bacterial spore at a distance. For the first time, the theory incorporates enhanced quantum coherence via femtosecond pulses and a nonlinear process into the classical scattering problem. Our result shows a large backscattered signal in the far field, using typical parameters of an anthrax spore with maximally prepared vibrational coherence. Using train pulses of 1 kHz of repetition rate each with energy of 10 mJ, we estimate that about 107 photons can be detected by a 1 m diameter detector placed 1 km away from the spore in the backward scattering direction. The result shows the feasibility of developing a real time remote detection of hazardous microparticles in the atmosphere, particularly biopathogenic spores.

  1. Theory of femtosecond coherent anti-Stokes Raman backscattering enhanced by quantum coherence for standoff detection of bacterial spores

    SciTech Connect

    Ooi, C.H. Raymond; Rostovtsev, Yuri; Scully, Marlan O.; Beadie, Guy; Reintjes, John F.; Kattawar, George W.; Zubairy, M. Suhail

    2005-08-15

    Backscattered signal of coherent anti-Stokes Raman spectroscopy can be an extremely useful tool for remote identification of airborne particles, provided the signal is sufficiently large. We formulate a semiclassical theory of nonlinear scattering to estimate the number of detectable photons from a bacterial spore at a distance. For the first time, the theory incorporates enhanced quantum coherence via femtosecond pulses and a nonlinear process into the classical scattering problem. Our result shows a large backscattered signal in the far field, using typical parameters of an anthrax spore with maximally prepared vibrational coherence. Using train pulses of 1 kHz of repetition rate each with energy of 10 mJ, we estimate that about 10{sup 7} photons can be detected by a 1 m diameter detector placed 1 km away from the spore in the backward scattering direction. The result shows the feasibility of developing a real time remote detection of hazardous microparticles in the atmosphere, particularly biopathogenic spores.

  2. Simultaneous observation of rotational coherent Stokes Raman scattering and coherent anti-Stokes Raman scattering in air and nitrogen

    NASA Technical Reports Server (NTRS)

    Snow, J. B.; Chang, R. K.; Zheng, J. B.; Leipertz, A.

    1983-01-01

    Rotational coherent Stokes Raman scattering (CSRS) and coherent anti-Stokes Raman scattering (CARS) in air and in nitrogen were observed simultaneously by using broadband generation and detection. In the broadband technique used, the entire CARS and CSRS spectrum was generated in a single laser pulse; the CSRS and CARS signals were dispersed by a spectrograph and detected simultaneously by an optical multichannel analyzer. A three-dimensional phase-matching geometry was used to achieve spatial resolution of the CSRS and CARS beams from the input beams. Under resonant conditions, similar experiments may provide a means of investigating the possible interaction between the CSRS and CARS processes in driving the rotational levels.

  3. Label-Free Cellular Imaging by Broadband Coherent Anti-Stokes Raman Scattering Microscopy

    PubMed Central

    Parekh, Sapun H.; Lee, Young Jong; Aamer, Khaled A.; Cicerone, Marcus T.

    2010-01-01

    Raman microspectroscopy can provide the chemical contrast needed to characterize the complex intracellular environment and macromolecular organization in cells without exogenous labels. It has shown a remarkable ability to detect chemical changes underlying cell differentiation and pathology-related chemical changes in tissues but has not been widely adopted for imaging, largely due to low signal levels. Broadband coherent anti-Stokes Raman scattering (B-CARS) offers the same inherent chemical contrast as spontaneous Raman but with increased acquisition rates. To date, however, only spectrally resolved signals from the strong CH-related vibrations have been used for CARS imaging. Here, we obtain Raman spectral images of single cells with a spectral range of 600–3200 cm−1, including signatures from weakly scattering modes as well as CH vibrations. We also show that B-CARS imaging can be used to measure spectral signatures of individual cells at least fivefold faster than spontaneous Raman microspectroscopy and can be used to generate maps of biochemical species in cells. This improved spectral range and signal intensity opens the door for more widespread use of vibrational spectroscopic imaging in biology and clinical diagnostics. PMID:20959111

  4. Interline Transfer CCD Camera for Gated Broadband Coherent Anti-Stokes Raman-Scattering Measurements.

    PubMed

    Roy, S; Ray, G; Lucht, R P

    2001-11-20

    Use of an interline transfer CCD camera for the acquisition of broadband coherent anti-Stokes Raman-scattering (CARS) spectra is demonstrated. The interline transfer CCD has alternating columns of imaging and storage pixels that allow one to acquire two successive images by shifting the first image in the storage pixels and immediately acquiring the second image. We have used this dual-image mode for gated CARS measurements by acquiring a CARS spectral image and shifting it rapidly from the imaging pixel columns to the storage pixel columns. We have demonstrated the use of this dual-image mode for gated single-laser-shot measurement of hydrogen and nitrogen CARS spectra at room temperature and in atmospheric pressure flames. The performance of the interline transfer CCD for these CARS measurements is compared directly with the performance of a back-illuminated unintensified CCD camera. PMID:18364895

  5. Simple approach to one-laser, broadband coherent anti-Stokes Raman scattering microscopy

    PubMed Central

    Kee, Tak W.; Cicerone, Marcus T.

    2014-01-01

    Coherent anti-Stokes Raman scattering (CARS) microscopy is emerging as a powerful method for imaging materials and biological systems, partly because of its noninvasiveness and selective chemical sensitivity. However, its full potential for species-selective imaging is limited by a restricted spectral bandwidth. Recent increases in bandwidth are promising but still are not sufficient for the level of robust component discrimination that would be needed in a chemically complex milieu found, for example, in intracellular and extracellular environments. We demonstrate a truly broadband CARS imaging instrument that we use to acquire hyper-spectral images with vibrational spectra over a bandwidth of 2500 cm−1 with a resolution of 13 cm−1. PMID:15605477

  6. Coherent anti-Stokes Raman scattering performed on expanding thermal arc plasmas

    NASA Astrophysics Data System (ADS)

    Meulenbroeks, R. F. G.; Engeln, R. A. H.; van der Mullen, J. A. M.; Schram, D. C.

    1996-05-01

    The expanding plasma emanating from a thermal arc plasma source that can be used for deposition of thin films is studied using laser spectroscopic techniques. The argon-hydrogen plasma is characterized by very fast recombination that cannot be explained by atomic processes. To explore this phenomenon, which has been related to wall association of hydrogen atoms and recirculation, CARS (coherent anti-Stokes Raman scattering) is performed on (argon-)hydrogen plasmas. The periphery of the plasma appears to be rich in hydrogen molecules, in accordance with the recirculation model. No highly rovibrationally excited states are detected in the periphery, in spite of the spectrometer's very good sensitivity (0.1 Pa H2 at 300 K). For the plasma, rotational and vibrational temperatures as well as absolute H2 densities are measured. A simple model for the observed (non-Boltzmann) rotational populations is developed.

  7. Coherent anti-Stokes Raman scattering performed on expanding thermal arc plasmas

    SciTech Connect

    Meulenbroeks, R.F.; Engeln, R.A.; van der Mullen, J.A.; Schram, D.C.

    1996-05-01

    The expanding plasma emanating from a thermal arc plasma source that can be used for deposition of thin films is studied using laser spectroscopic techniques. The argon-hydrogen plasma is characterized by very fast recombination that cannot be explained by atomic processes. To explore this phenomenon, which has been related to wall association of hydrogen atoms and recirculation, CARS (coherent anti-Stokes Raman scattering) is performed on (argon-)hydrogen plasmas. The periphery of the plasma appears to be rich in hydrogen molecules, in accordance with the recirculation model. No highly rovibrationally excited states are detected in the periphery, in spite of the spectrometer{close_quote}s very good sensitivity (0.1 Pa H{sub 2} at 300 K). For the plasma, rotational and vibrational temperatures as well as absolute H{sub 2} densities are measured. A simple model for the observed (non-Boltzmann) rotational populations is developed. {copyright} {ital 1996 The American Physical Society.}

  8. Automated Identification of Subcellular Organelles by Coherent Anti-Stokes Raman Scattering

    PubMed Central

    El-Mashtoly, Samir F.; Niedieker, Daniel; Petersen, Dennis; Krauss, Sascha D.; Freier, Erik; Maghnouj, Abdelouahid; Mosig, Axel; Hahn, Stephan; Kötting, Carsten; Gerwert, Klaus

    2014-01-01

    Coherent anti-Stokes Raman scattering (CARS) is an emerging tool for label-free characterization of living cells. Here, unsupervised multivariate analysis of CARS datasets was used to visualize the subcellular compartments. In addition, a supervised learning algorithm based on the “random forest” ensemble learning method as a classifier, was trained with CARS spectra using immunofluorescence images as a reference. The supervised classifier was then used, to our knowledge for the first time, to automatically identify lipid droplets, nucleus, nucleoli, and endoplasmic reticulum in datasets that are not used for training. These four subcellular components were simultaneously and label-free monitored instead of using several fluorescent labels. These results open new avenues for label-free time-resolved investigation of subcellular components in different cells, especially cancer cells. PMID:24806923

  9. Investigation of microstructured chitosans by coherent anti-Stokes Raman microscopy.

    PubMed

    Dementjev, A; Mordas, G; Ulevičius, V; Gulbinas, V

    2015-03-01

    This work describes application of coherent anti-Stokes Raman scattering (CARS) microscopy technique for analytical characterization of microstructured materials based on chitosan. We demonstrate that nitrogen-hydrogen vibration band in the high wavenumber region of CARS spectrum prevails over response from oxygen-hydrogen vibrations and can be used as a spectral marker of chitosan. The chemically selective imaging is experimentally demonstrated by applying CARS microscopy to discriminate between chitosan and polystyrene microparticles. CARS microscopy was shown to be a valuable tool for characterization of polluted chitosan fibre from utilized engine filter material. A possibility to observe foreign material pieces on the surface of the polluted chitosan fibre is demonstrated and discussed. PMID:25529768

  10. High-resolution extreme-ultraviolet spectroscopy of potassium using anti-Stokes radiation

    NASA Technical Reports Server (NTRS)

    Rothenberg, J. E.; Young, J. F.; Harris, S. E.

    1981-01-01

    The use of a new extreme-ultraviolet radiation source based on spontaneous anti-Stokes scattering for high-resolution absorption spectroscopy of transition originating from the 3p6 shell of potassium is reported. The region from 546.6 to 536.8 A is scanned at a resolution of about 1.2 Kayser. Within this region, four previously unreported lines are observed.

  11. Diffraction barrier breakthrough in coherent anti-Stokes Raman scattering microscopy by additional probe-beam-induced phonon depletion

    SciTech Connect

    Liu Wei; Niu Hanben

    2011-02-15

    We provide an approach to significantly break the diffraction limit in coherent anti-Stokes Raman scattering (CARS) microscopy via an additional probe-beam-induced photon depletion (APIPD). The additional probe beam, whose profile is doughnut shaped and whose wavelength is different from the Gaussian probe beam, depletes the phonons to yield an unwanted anti-Stokes signal within a certain bandwidth at the rim of the diffraction-limited spot. When the Gaussian probe beam that follows immediately arrives, no anti-Stokes signal is generated in this region, resembling stimulated emission depletion (STED) microscopy, and the spot-generating useful anti-Stokes signals by this beam are substantially suppressed to a much smaller dimension. Scanning the spot renders three-dimensional, label-free, and chemically selective CARS images with subdiffraction resolution. Also, resolution-enhanced images of the molecule, specified by its broadband even-total CARS spectral signals not only by one anti-Stokes signal for its special chemical bond, can be obtained by employing a supercontinuum source.

  12. Efficient anti-Stokes generation via intermodal stimulated Raman scattering in gas-filled hollow-core PCF.

    PubMed

    Trabold, B M; Abdolvand, A; Euser, T G; Russell, P St J

    2013-12-01

    A strong anti-Stokes Raman signal, from the vibrational Q(1) transition of hydrogen, is generated in gas-filled hollow-core photonic crystal fiber. To be efficient, this process requires phase-matching, which is not automatically provided since the group velocity dispersion is typically non-zero and--inside a fiber--cannot be compensated for using a crossed-beam geometry. Phase-matching can however be arranged by exploiting the different dispersion profiles of higher-order modes. We demonstrate the generation of first and second anti-Stokes signals in higher-order modes by pumping with an appropriate mixture of fundamental and a higher-order modes, synthesized using a spatial light modulator. Conversion efficiencies as high as 5.3% are achieved from the pump to the first anti-Stokes band. PMID:24514522

  13. Hyperspectral microscopic imaging by multiplex coherent anti-Stokes Raman scattering (CARS)

    NASA Astrophysics Data System (ADS)

    Khmaladze, Alexander; Jasensky, Joshua; Zhang, Chi; Han, Xiaofeng; Ding, Jun; Seeley, Emily; Liu, Xinran; Smith, Gary D.; Chen, Zhan

    2011-10-01

    Coherent anti-Stokes Raman scattering (CARS) microscopy is a powerful technique to image the chemical composition of complex samples in biophysics, biology and materials science. CARS is a four-wave mixing process. The application of a spectrally narrow pump beam and a spectrally wide Stokes beam excites multiple Raman transitions, which are probed by a probe beam. This generates a coherent directional CARS signal with several orders of magnitude higher intensity relative to spontaneous Raman scattering. Recent advances in the development of ultrafast lasers, as well as photonic crystal fibers (PCF), enable multiplex CARS. In this study, we employed two scanning imaging methods. In one, the detection is performed by a photo-multiplier tube (PMT) attached to the spectrometer. The acquisition of a series of images, while tuning the wavelengths between images, allows for subsequent reconstruction of spectra at each image point. The second method detects CARS spectrum in each point by a cooled coupled charged detector (CCD) camera. Coupled with point-by-point scanning, it allows for a hyperspectral microscopic imaging. We applied this CARS imaging system to study biological samples such as oocytes.

  14. Fast spectral coherent anti-Stokes Raman scattering microscopy with high-speed tunable picosecond laser.

    PubMed

    Cahyadi, Harsono; Iwatsuka, Junichi; Minamikawa, Takeo; Niioka, Hirohiko; Araki, Tsutomu; Hashimoto, Mamoru

    2013-09-01

    We develop a coherent anti-Stokes Raman scattering (CARS) microscopy system equipped with a tunable picosecond laser for high-speed wavelength scanning. An acousto-optic tunable filter (AOTF) is integrated in the laser cavity to enable wavelength scanning by varying the radio frequency waves applied to the AOTF crystal. An end mirror attached on a piezoelectric actuator and a pair of parallel plates driven by galvanometer motors are also introduced into the cavity to compensate for changes in the cavity length during wavelength scanning to allow synchronization with another picosecond laser. We demonstrate fast spectral imaging of 3T3-L1 adipocytes every 5  cm-1 in the Raman spectral region around 2850  cm-1 with an image acquisition time of 120 ms. We also demonstrate fast switching of Raman shifts between 2100 and 2850  cm-1, corresponding to CD2 symmetric stretching and CH2 symmetric stretching vibrations, respectively. The fast-switching CARS images reveal different locations of recrystallized deuterated and nondeuterated stearic acid. PMID:24013358

  15. Saturation of vibrational coherent anti-Stokes Raman scattering mediated by saturation of the rotational Raman transition

    NASA Astrophysics Data System (ADS)

    Patnaik, Anil K.; Roy, Sukesh; Gord, James R.

    2013-04-01

    Saturation of vibrational Raman coherence and coherent anti-Stokes Raman scattering (CARS) using femtosecond (fs) excitation pulses is investigated theoretically. The pump in a typical fs-CARS configuration has a bandwidth of a few hundred cm-1 that can couple tens of rotational states of room-air nitrogen molecules simultaneously, unlike in CARS with longer pulse durations. It is demonstrated that the vibrational coherence and also the vibrational CARS with fs excitation display saturationlike behavior once the rotational coherence is saturated. The Raman saturation threshold for the fs pump is numerically estimated to be at a peak intensity of ˜1022 W/m2, which is six to seven orders of magnitude higher than that in the nanosecond regime. The results are compared with the known saturation thresholds in different pulse-duration regimes and placed in perspective with other nonlinear thresholds reported in fs excitation regimes.

  16. Coherent anti-Stokes Raman scattering enhancement of thymine adsorbed on graphene oxide

    PubMed Central

    2014-01-01

    Coherent anti-Stokes Raman scattering (CARS) of carbon nanostructures, namely, highly oriented pyrolytic graphite, graphene nanoplatelets, graphene oxide, and multiwall carbon nanotubes as well CARS spectra of thymine (Thy) molecules adsorbed on graphene oxide were studied. The spectra of the samples were compared with spontaneous Raman scattering (RS) spectra. The CARS spectra of Thy adsorbed on graphene oxide are characterized by shifts of the main bands in comparison with RS. The CARS spectra of the initial nanocarbons are definitely different: for all investigated materials, there is a redistribution of D- and G-mode intensities, significant shift of their frequencies (more than 20 cm-1), and appearance of new modes about 1,400 and 1,500 cm-1. The D band in CARS spectra is less changed than the G band; there is an absence of 2D-mode at 2,600 cm-1 for graphene and appearance of intensive modes of the second order between 2,400 and 3,000 cm-1. Multiphonon processes in graphene under many photon excitations seem to be responsible for the features of the CARS spectra. We found an enhancement of the CARS signal from thymine adsorbed on graphene oxide with maximum enhancement factor about 105. The probable mechanism of CARS enhancement is discussed. PMID:24948887

  17. Sparse sampling for fast hyperspectral coherent anti-Stokes Raman scattering imaging.

    PubMed

    Masia, Francesco; Borri, Paola; Langbein, Wolfgang

    2014-02-24

    We demonstrate a method to increase the acquisition speed in coherent anti-Stokes Raman scattering (CARS) hyperspectral imaging while retaining the relevant spectral information. The method first determines the important spectral components of a sample from a hyper-spectral image over a small number of spatial points but a large number of spectral points covering the accessible spectral range and sampling the instrument spectral resolution at the Nyquist limit. From these components we determine a small set of frequencies needed to retrieve the weights of the components with minimum error for a given measurement noise. Hyperspectral images with a large number of spatial points, for example covering a large spatial region, are then measured at this small set of frequencies, and a reconstruction algorithm is applied to generate the full spectral range and resolution. The resulting spectra are suited to retrieve from the CARS intensity the CARS susceptibility which is linear in the concentration, and apply unsupervised quantitative analysis methods such as FSC3. We demonstrate the method on CARS hyperspectral images of human osteosarcoma U2OS cell, with a reduction in the acquisition time by a factor of 25. This method is suited also for other coherent vibrational microscopy techniques such as stimulated Raman scattering, and in general for hyperspectral imaging techniques with sequential spectral acquisition. PMID:24663723

  18. Nanosecond coherent anti-Stokes Raman scattering for particle size characterization

    NASA Astrophysics Data System (ADS)

    El Bassri, Farid; Lefort, Claire; Capitaine, Erwan; Louot, Christophe; Pagnoux, Dominique; Couderc, Vincent; Leproux, Philippe

    2016-03-01

    Particle size analyzers based on laser scattering commonly make use of light diffraction and scattering around the particle considered in its medium. For particle size below 50 μm, Fraunhofer theory must be abandoned in favor of Mie model, which requires to know the complex refractive index of both the particle and the medium. In this paper, we demonstrate that particle size characterization can be realized by measuring the macroscopic Raman spectral response of the whole set of particles excited by a laser beam. We use a home-made setup based on coherent anti-Stokes Raman scattering (CARS) and having a 0.36 cm-1 spectral resolution, in which the laser source is a dual-output infrared nanosecond supercontinuum source (1064 nm monochromatic pump wave, 1100-1640 nm broadband Stokes wave). The samples are latex beads in water with different diameters (20 nm, 50 nm, 100 nm, 5 μm). The C-H stretching line around 3050 cm-1 is studied. For this vibration, we study the variation of both the CARS central frequency and linewidth as a function of the particles size. A quasi linear increase of the linewidth with the inverse of the diameter is measured. A difference of 15 cm-1 is obtained between beads with diameters of 5 μm and 20 nm respectively. The physical phenomena at the origin of this difference are discussed, especially considering the contributions of the center and of the boundaries of the object to the global Raman response.

  19. Coherent anti-Stokes Raman scattering microscopy of human smooth muscle cells in bioengineered tissue scaffolds

    NASA Astrophysics Data System (ADS)

    Brackmann, Christian; Esguerra, Maricris; Olausson, Daniel; Delbro, Dick; Krettek, Alexandra; Gatenholm, Paul; Enejder, Annika

    2011-02-01

    The integration of living, human smooth muscle cells in biosynthesized cellulose scaffolds was monitored by nonlinear microscopy toward contractile artificial blood vessels. Combined coherent anti-Stokes Raman scattering (CARS) and second harmonic generation (SHG) microscopy was applied for studies of the cell interaction with the biopolymer network. CARS microscopy probing CH2-groups at 2845 cm-1 permitted three-dimensional imaging of the cells with high contrast for lipid-rich intracellular structures. SHG microscopy visualized the fibers of the cellulose scaffold, together with a small signal obtained from the cytoplasmic myosin of the muscle cells. From the overlay images we conclude a close interaction between cells and cellulose fibers. We followed the cell migration into the three-dimensional structure, illustrating that while the cells submerge into the scaffold they extrude filopodia on top of the surface. A comparison between compact and porous scaffolds reveals a migration depth of <10 μm for the former, whereas the porous type shows cells further submerged into the cellulose. Thus, the scaffold architecture determines the degree of cell integration. We conclude that the unique ability of nonlinear microscopy to visualize the three-dimensional composition of living, soft matter makes it an ideal instrument within tissue engineering.

  20. Dual-Pump Coherent Anti-Stokes Raman Scattering Temperature and CO2 Concentration Measurements

    NASA Technical Reports Server (NTRS)

    Lucht, Robert P.; Velur-Natarajan, Viswanathan; Carter, Campbell D.; Grinstead, Keith D., Jr.; Gord, James R.; Danehy, Paul M.; Fiechtner, G. J.; Farrow, Roger L.

    2003-01-01

    Measurements of temperature and CO2 concentration using dual-pump coherent anti-Stokes Raman scattering, (CARS) are described. The measurements were performed in laboratory flames,in a room-temperature gas cell, and on an engine test stand at the U.S. Air Force Research Laboratory, Wright-Patterson Air Force Base. A modeless dye laser, a single-mode Nd:YAG laser, and an unintensified back-illuminated charge-coupled device digital camera were used for these measurements. The CARS measurements were performed on a single-laser-shot basis. The standard deviations of the temperatures and CO2 mole fractions determined from single-shot dual-pump CARS spectra in steady laminar propane/air flames were approximately 2 and 10% of the mean values of approximately 2000 K and 0.10, respectively. The precision and accuracy of single-shot temperature measurements obtained from the nitrogen part of the dual-pump CARS system were investigated in detail in near-adiabatic hydrogen/air/CO2 flames. The precision of the CARS temperature measurements was found to be comparable to the best results reported in the literature for conventional two-laser, single-pump CARS. The application of dual-pump CARS for single-shot measurements in a swirl-stabilized combustor fueled with JP-8 was also demonstrated.

  1. Investigation of lipid homeostasis in living Drosophila by coherent anti-Stokes Raman scattering microscopy

    NASA Astrophysics Data System (ADS)

    Chien, Cheng-Hao; Chen, Wei-Wen; Wu, June-Tai; Chang, Ta-Chau

    2012-12-01

    To improve our understanding of lipid metabolism, Drosophila is used as a model animal, and its lipid homeostasis is monitored by coherent anti-Stokes Raman scattering microscopy. We are able to achieve in vivo imaging of larval fat body (analogous to adipose tissue in mammals) and oenocytes (analogous to hepatocytes) in Drosophila larvae at subcellular level without any labeling. By overexpressing two lipid regulatory proteins-Brummer lipase (Bmm) and lipid storage droplet-2 (Lsd-2)-we found different phenotypes and responses under fed and starved conditions. Comparing with the control larva, we observed more lipid droplet accumulation by ˜twofold in oenocytes of fat-body-Bmm-overexpressing (FB-Bmm-overexpressing) mutant under fed condition, and less lipid by ˜fourfold in oenocytes of fat-body-Lsd-2-overexpressing (FB-Lsd-2-overexpressing) mutant under starved condition. Moreover, together with reduced size of lipid droplets, the lipid content in the fat body of FB-Bmm-overexpressing mutant decreases much faster than that of the control and FB-Lsd-2-overexpressing mutant during starvation. From long-term starvation assay, we found FB-Bmm-overexpressing mutant has a shorter lifespan, which can be attributed to faster consumption of lipid in its fat body. Our results demonstrate in vivo observations of direct influences of Bmm and Lsd-2 on lipid homeostasis in Drosophila larvae.

  2. Surfactant Uptake Dynamics in Mammalian Cells Elucidated with Quantitative Coherent Anti-Stokes Raman Scattering Microspectroscopy

    PubMed Central

    Okuno, Masanari; Kano, Hideaki; Fujii, Kenkichi; Bito, Kotatsu; Naito, Satoru; Leproux, Philippe; Couderc, Vincent; Hamaguchi, Hiro-o

    2014-01-01

    The mechanism of surfactant-induced cell lysis has been studied with quantitative coherent anti-Stokes Raman scattering (CARS) microspectroscopy. The dynamics of surfactant molecules as well as intracellular biomolecules in living Chinese Hamster Lung (CHL) cells has been examined for a low surfactant concentration (0.01 w%). By using an isotope labeled surfactant having CD bonds, surfactant uptake dynamics in living cells has been traced in detail. The simultaneous CARS imaging of the cell itself and the internalized surfactant has shown that the surfactant molecules is first accumulated inside a CHL cell followed by a sudden leak of cytosolic components such as proteins to the outside of the cell. This finding indicates that surfactant uptake occurs prior to the cell lysis, contrary to what has been believed: surface adsorption of surfactant molecules has been thought to occur first with subsequent disruption of cell membranes. Quantitative CARS microspectroscopy enables us to determine the molecular concentration of the surfactant molecules accumulated in a cell. We have also investigated the effect of a drug, nocodazole, on the surfactant uptake dynamics. As a result of the inhibition of tubulin polymerization by nocodazole, the surfactant uptake rate is significantly lowered. This fact suggests that intracellular membrane trafficking contributes to the surfactant uptake mechanism. PMID:24710120

  3. Imaging the Intact Mouse Cornea Using Coherent Anti-Stokes Raman scattering (CARS)

    PubMed Central

    Ammar, David A.; Lei, Tim C.; Kahook, Malik Y.; Masihzadeh, Omid

    2013-01-01

    Purpose. The aim of this study was to image the cellular and noncellular structures of the cornea and limbus in an intact mouse eye using the vibrational oscillation of the carbon–hydrogen bond in lipid membranes and autofluorescence as label-free contrast agents. Methods. Freshly enucleated mouse eyes were imaged using two nonlinear optical techniques: coherent anti-Stokes Raman scattering (CARS) and two-photon autofluorescence (TPAF). Sequential images were collected through the full thickness of the cornea and limbal regions. Line scans along the transverse/sagittal axes were also performed. Results. Analysis of multiple CARS/TPAF images revealed that corneal epithelial and endothelial cells could be identified by the lipid-rich plasma membrane CARS signal. The fluorescent signal from the collagen fibers of the corneal stroma was evident in the TPAF channel. The transition from the cornea to sclera at the limbus was marked by a change in collagen pattern (TPAF channel) and thickness of surface cells (CARS channel). Regions within the corneal stroma that lack collagen autofluorescence coincided with CARS signal, indicating the presence of stromal fibroblasts or nerve fibers. Conclusions. The CARS technique was successful in imaging cells in the intact mouse eye, both at the surface and within corneal tissue. Multiphoton images were comparable to histologic sections. The methods described here represent a new avenue for molecular specific imaging of the mouse eye. The lack of need for tissue fixation is unique compared with traditional histology imaging techniques. PMID:23821187

  4. Coherent Anti-Stokes Raman Scattering (CARS) Microscopy: A Novel Technique for Imaging the Retina

    PubMed Central

    Masihzadeh, Omid; Ammar, David A.; Kahook, Malik Y.; Lei, Tim C.

    2013-01-01

    Purpose. To image the cellular and noncellular structures of the retina in an intact mouse eye without the application of exogenous fluorescent labels using noninvasive, nondestructive techniques. Methods. Freshly enucleated mouse eyes were imaged using two nonlinear optical techniques: coherent anti-Stokes Raman scattering (CARS) and two-photon autofluorescence (TPAF). Cross sectional transverse sections and sequential flat (en face) sagittal sections were collected from a region of sclera approximately midway between the limbus and optic nerve. Imaging proceeded from the surface of the sclera to a depth of ∼60 μm. Results. The fluorescent signal from collagen fibers within the sclera was evident in the TPAF channel; the scleral collagen fibers showed no organization and appeared randomly packed. The sclera contained regions lacking TPAF and CARS fluorescence of ∼3 to 15 μm in diameter that could represent small vessels or scleral fibroblasts. Intense punctate CARS signals from the retinal pigment epithelial layer were of a size and shape of retinyl storage esters. Rod outer segments could be identified by the CARS signal from their lipid-rich plasma membranes. Conclusions. CARS microscopy can be used to image the outer regions of the mammalian retina without the use of a fluorescent dye or exogenously expressed recombinant protein. With technical advancements, CARS/TPAF may represent a new avenue for noninvasively imaging the retina and might complement modalities currently used in clinical practice. PMID:23580484

  5. Coherent anti-Stokes Raman scattering hyperspectral imaging of cartilage aiming for state discrimination of cell

    NASA Astrophysics Data System (ADS)

    Shiozawa, Manabu; Shirai, Masataka; Izumisawa, Junko; Tanabe, Maiko; Watanabe, Koich

    2016-07-01

    Noninvasive cell analyses are increasingly important in the medical field. A coherent anti-Stokes Raman scattering (CARS) microscope is the noninvasive imaging equipment and enables to obtain images indicating molecular distribution. However, due to low-signal intensity, it is still challenging to obtain images of the fingerprint region, in which many spectrum peaks correspond to compositions of a cell. Here, to identify cell differentiation by using multiplex CARS, we investigated hyperspectral imaging of the fingerprint region of living cells. To perform multiplex CARS, we used a prototype of a compact light source generating both pump light and broadband Stokes light. Assuming application to regenerative medicine, we chose a cartilage cell, whose differentiation is difficult to be identified by change of the cell morphology. Because one of the major components of cartilage is collagen, we focused on distribution of proline, which accounts for approximately 20% of collagen. The spectrum quality was improved by optical adjustments of the power branching ratio and divergence of Stokes light. Periphery of a cartilage cell was highlighted in a CARS image of proline, and this result suggests correspondence with collagen generated as an extracellular matrix. The possibility of noninvasive analyses by using CARS hyperspectral imaging was indicated.

  6. Coherent anti-Stokes Raman scattering microscopy driving the future of loaded mesoporous silica imaging.

    PubMed

    Fussell, Andrew L; Mah, Pei Ting; Offerhaus, Herman; Niemi, Sanna-Mari; Salonen, Jarno; Santos, Hélder A; Strachan, Clare

    2014-11-01

    This study reports the use of variants of coherent anti-Stokes Raman scattering (CARS) microscopy as a novel method for improved physicochemical characterization of drug-loaded silica particles. Ordered mesoporous silica is a biomaterial that can be loaded to carry a number of biochemicals, including poorly water-soluble drugs, by allowing the incorporation of drug into nanometer-sized pores. In this work, the loading of two poorly water-soluble model drugs, itraconazole and griseofulvin, in MCM-41 silica microparticles is characterized qualitatively, using the novel approach of CARS microscopy, which has advantages over other analytical approaches used to date and is non-destructive, rapid, label free, confocal and has chemical and physical specificity. The study investigated the effect of two solvent-based loading methods, namely immersion and rotary evaporation, and microparticle size on the three-dimensional (3-D) distribution of the two loaded drugs. Additionally, hyperspectral CARS microscopy was used to confirm the amorphous nature of the loaded drugs. Z-stacked CARS microscopy suggested that the drug, but not the loading method or particle size range, affected 3-D drug distribution. Hyperspectral CARS confirmed that the drug loaded in the MCM-41 silica microparticles was in an amorphous form. The results show that CARS microscopy and hyperspectral CARS microscopy can be used to provide further insights into the structural nature of loaded mesoporous silica microparticles as biomaterials. PMID:25064000

  7. Highly selective standoff detection and imaging of trace chemicals in a complex background using single-beam coherent anti-Stokes Raman scattering

    NASA Astrophysics Data System (ADS)

    Bremer, Marshall T.; Wrzesinski, Paul J.; Butcher, Nathan; Lozovoy, Vadim V.; Dantus, Marcos

    2011-09-01

    A non-destructive and highly selective method of standoff detection is presented and quantitatively evaluated. The method is found to be orders of magnitude more sensitive than previous coherent spectroscopy methods, identifying concentrations as low as 2 μg/cm2 of an explosive simulant mixed in a polymer matrix. The approach uses a single amplified femtosecond laser to generate high-resolution multiplex coherent anti-Stokes Raman scattering (CARS) spectra encompassing the fingerprint region (400-2500 cm-1) at standoff distance. Additionally, a standoff imaging modality is introduced, visually demonstrating similar sensitivity and high selectivity, providing promising results toward highly selective trace detection of explosives or warfare agents.

  8. Hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering for gas-phase temperature measurements

    NASA Astrophysics Data System (ADS)

    Miller, Joseph Daniel

    Hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps CARS) is employed for quantitative gas-phase temperature measurements in combustion processes and heated flows. In this approach, ultrafast 100-fs laser pulses are used to induce vibrational and rotational transitions in N2 and O2, while a third spectrally narrowed picosecond pulse is used to probe the molecular response. Temporal suppression of the nonresonant contribution and elimination of collisional effects are achieved by delay of the probe pulse, while sufficient spectral resolution is maintained for frequency-domain detection and thermometry. A theoretical framework is developed to model experimental spectra by phenomenologically describing the temporal evolution of the vibrational and rotational wavepackets as a function of temperature and pressure. Interference-free, single-shot vibrational fs/ps CARS thermometry is demonstrated at 1-kHz from 1400-2400 K in a H2-air flame, with accuracy better than 3%. A time-asymmetric exponential pulse shape is introduced to optimize nonresonant suppression with a 103 reduction at a probe delay of 0.31 ps. Low-temperature single-shot thermometry (300-700 K) with better than 1.5% accuracy is demonstrated using a fully degenerate rotational fs/ps CARS scheme, and the influence of collision energy transfer on thermometry error is quantified at atmospheric pressure. Interference-free thermometry, without nonresonant contributions and collision-induced error, is demonstrated for the first time using rotational fs/ps CARS at room temperature and pressures from 1-15 atm. Finally, the temporal and spectral resolution of fs/ps CARS is exploited for transition-resolved time-domain measurements of N2 and O2 self-broadened S-branch Raman linewidths at pressures of 1-20 atm.

  9. Selective probing of vibrational hot states in bromine using time-resolved coherent anti-Stokes Raman scattering.

    PubMed

    Namboodiri, Mahesh; Liebers, Jörg; Kleinekathöfer, Ulrich; Materny, Arnulf

    2012-11-26

    In previous work (Scaria, A.; et al. Chem. Phys. Lett. 2009, 470, 39-43) it was shown that the excitation of the electronic B state in bromine can be characterized by transitions starting from vibrational hot states of the electronic ground X state. This contribution is strongly depending on the specific Franck-Condon factors for the chosen wavelength (in that work 540 nm) used for excitation. For the investigation of the resulting excited state dynamics, a pump-degenerate four-wave mixing (pump-DFWM) experiment was applied. To increase the vibrational selectivity, in the present work we have performed temperature-dependent time-resolved coherent anti-Stokes Raman scattering (CARS) spectroscopy to probe the B state dynamics of bromine. Also here, the wavelength of the excitation (in this case, the pump laser of the CARS process) was set to 540 nm for all measurements. The hot state contribution is small, even at high temperatures. It can be probed by tuning the Stokes wavelength to resonance. The time delay between the probe pulse and the time-coincident pump/Stokes pulse pair of the CARS process is scanned, giving access to the wave packet dynamics in the excited B state. The experimental observations are supported by quantum dynamical calculations. PMID:22757648

  10. Coherent Anti-Stokes Raman Scattering (CARS) as a Probe for Supersonic Hydrogen-Fuel/Air Mixing

    NASA Technical Reports Server (NTRS)

    Danehy, P. M.; O'Byrne, S.; Cutler, A. D.; Rodriguez, C. G.

    2003-01-01

    The dual-pump coherent anti-Stokes Raman spectroscopy (CARS) method was used to measure temperature and the absolute mole fractions of N2, O2 and H2 in a supersonic non-reacting fuel-air mixing experiment. Experiments were conducted in NASA Langley Research Center s Direct Connect Supersonic Combustion Test Facility. Under normal operation of this facility, hydrogen and air burn to increase the enthalpy of the test gas and O2 is added to simulate air. This gas is expanded through a Mach 2 nozzle and into a combustor model where fuel is then injected, mixes and burns. In the present experiment the O2 of the test gas is replaced by N2. The lack of oxidizer inhibited combustion of the injected H2 fuel jet allowing the fuel/air mixing process to be studied. CARS measurements were performed 427 mm downstream of the nozzle exit and 260 mm downstream of the fuel injector. Maps were obtained of the mean temperature, as well as the N2, O2 and H2 mean mole fraction fields. A map of mean H2O vapor mole fraction was also inferred from these measurements. Correlations between different measured parameters and their fluctuations are presented. The CARS measurements are compared with a preliminary computational prediction of the flow.

  11. Chemical imaging of tissue in vivo with video-rate coherent anti-Stokes Raman scattering microscopy

    PubMed Central

    Evans, Conor L.; Potma, Eric O.; Puoris'haag, Mehron; Côté, Daniel; Lin, Charles P.; Xie, X. Sunney

    2005-01-01

    Imaging living organisms with molecular selectivity typically requires the introduction of specific labels. Many applications in biology and medicine, however, would significantly benefit from a noninvasive imaging technique that circumvents such exogenous probes. In vivo microscopy based on vibrational spectroscopic contrast offers a unique approach for visualizing tissue architecture with molecular specificity. We have developed a sensitive technique for vibrational imaging of tissues by combining coherent anti-Stokes Raman scattering (CARS) with video-rate microscopy. Backscattering of the intense forward-propagating CARS radiation in tissue gives rise to a strong epi-CARS signal that makes in vivo imaging possible. This substantially large signal allows for real-time monitoring of dynamic processes, such as the diffusion of chemical compounds, in tissues. By tuning into the CH2 stretching vibrational band, we demonstrate CARS imaging and spectroscopy of lipid-rich tissue structures in the skin of a live mouse, including sebaceous glands, corneocytes, and adipocytes, with unprecedented contrast at subcellular resolution. PMID:16263923

  12. Hybrid single-source online Fourier transform coherent anti-Stokes Raman scattering/optical coherence tomography.

    PubMed

    Kamali, Tschackad; Považay, Boris; Kumar, Sunil; Silberberg, Yaron; Hermann, Boris; Werkmeister, René; Drexler, Wolfgang; Unterhuber, Angelika

    2014-10-01

    We demonstrate a multimodal optical coherence tomography (OCT) and online Fourier transform coherent anti-Stokes Raman scattering (FTCARS) platform using a single sub-12 femtosecond (fs) Ti:sapphire laser enabling simultaneous extraction of structural and chemical ("morphomolecular") information of biological samples. Spectral domain OCT prescreens the specimen providing a fast ultrahigh (4×12  μm axial and transverse) resolution wide field morphologic overview. Additional complementary intrinsic molecular information is obtained by zooming into regions of interest for fast label-free chemical mapping with online FTCARS spectroscopy. Background-free CARS is based on a Michelson interferometer in combination with a highly linear piezo stage, which allows for quick point-to-point extraction of CARS spectra in the fingerprint region in less than 125 ms with a resolution better than 4  cm(-1) without the need for averaging. OCT morphology and CARS spectral maps indicating phosphate and carbonate bond vibrations from human bone samples are extracted to demonstrate the performance of this hybrid imaging platform. PMID:25360965

  13. Polyglutamine aggregate structure in vitro and in vivo; new avenues for coherent anti-Stokes Raman scattering microscopy.

    PubMed

    Perney, Nicolas M; Braddick, Lucy; Jurna, Martin; Garbacik, Erik T; Offerhaus, Herman L; Serpell, Louise C; Blanch, Ewan; Holden-Dye, Lindy; Brocklesby, William S; Melvin, Tracy

    2012-01-01

    Coherent anti-Stokes Raman scattering (CARS) microscopy is applied for the first time for the evaluation of the protein secondary structure of polyglutamine (polyQ) aggregates in vivo. Our approach demonstrates the potential for translating information about protein structure that has been obtained in vitro by X-ray diffraction into a microscopy technique that allows the same protein structure to be detected in vivo. For these studies, fibres of polyQ containing peptides (D(2)Q(15)K(2)) were assembled in vitro and examined by electron microscopy and X-ray diffraction methods; the fibril structure was shown to be cross β-sheet. The same polyQ fibres were evaluated by Raman spectroscopy and this further confirmed the β-sheet structure, but indicated that the structure is highly rigid, as indicated by the strong Amide I signal at 1659 cm(-1). CARS spectra were simulated using the Raman spectrum taking into account potential non-resonant contributions, providing evidence that the Amide I signal remains strong, but slightly shifted to lower wavenumbers. Combined CARS (1657 cm(-1)) and multi-photon fluorescence microscopy of chimeric fusions of yellow fluorescent protein (YFP) with polyQ (Q40) expressed in the body wall muscle cells of Caenorhabditis elegans nematodes (1 day old adult hermaphrodites) revealed diffuse and foci patterns of Q40-YFP that were both fluorescent and exhibited stronger CARS (1657 cm(-1)) signals than in surrounding tissues at the resonance for the cross β-sheet polyQ in vitro. PMID:22911702

  14. Diagnosing lung cancer using coherent anti-Stokes Raman scattering microscopy

    NASA Astrophysics Data System (ADS)

    Gao, Liang; Yang, Yaliang; Xing, Jiong; Thrall, Michael J.; Wang, Zhiyong; Li, Fuhai; Luo, Pengfei; Wong, Kelvin K.; Zhao, Hong; Wong, Stephen T. C.

    2011-03-01

    Lung carcinoma is the most prevalent type of cancer in the world, and it is responsible for more deaths than other types of cancer. During diagnosis, a pathologist primarily aims to differentiate small cell carcinoma from non-small cell carcinoma on biopsy and cytology specimens, which is time consuming due to the time required for tissue processing and staining. To speed up the diagnostic process, we investigated the feasibility of using coherent anti-Stokes Raman scattering (CARS) microscopy as a label-free strategy to image lung lesions and differentiate subtypes of lung cancers. Different mouse lung cancer models were developed by injecting human lung cancer cell lines, including adenocarcinoma, squamous cell carcinoma, and small cell carcinoma, into lungs of the nude mice. CARS images were acquired from normal lung tissues and different subtypes of cancer lesions ex vivo using intrinsic contrasts from symmetric CH2 bonds. These images showed good correlation with the hematoxylin and eosin (H&E) stained sections from the same tissue samples with regard to cell size, density, and cell-cell distance. These features are routinely used in diagnosing lung lesions. Our results showed that the CARS technique is capable of providing a visualizable platform to differentiate different kinds of lung cancers using the same pathological features without histological staining and thus has the potential to serve as a more efficient examination tool for diagnostic pathology. In addition, incorporating with suitable fiber-optic probes would render the CARS technique as a promising approach for in vivo diagnosis of lung cancer.

  15. Fiber bundle based probe with polarization for coherent anti-Stokes Raman scattering microendoscopy imaging

    NASA Astrophysics Data System (ADS)

    Liu, Zhengfan; Wang, Zhiyong; Wang, Xi; Xu, Xiaoyun; Chen, Xu; Cheng, Jie; Li, Xiaoyan; Chen, Shufen; Xin, Jianguo; Wong, Stephen T. C.

    2013-02-01

    The ability to visualize cellular structures and tissue molecular signatures in a live body could revolutionize the practice of surgery. Specifically, such technology is promising for replacing tissue extraction biopsy and offering new strategies for a broad range of intraoperative or surgical applications, including early cancer detection, tumor margin identification, nerve damage avoidance, and surgical outcomes enhancement. Coherent anti-Stokes Raman scattering (CARS) microendoscopy offers a way to achieve this with label-free imaging capability and sub-cellular resolution. However, efficient collection of epi-CARS signals and reduction of nonlinear effects in fibers are two major challenges encountered in the development of fiber-based CARS microendoscopy. To circumvent this problem, we designed and developed a fiber bundle for a CARS microendoscopy prototype. The excitation lasers were delivered by a single multimode fiber at the center of the bundle while the epi-CARS signals were collected by multiple MMFs surrounding the central fiber. A polarization scheme was employed to suppress the four-wave mixing (FWM) effect in the excitation fiber. Our experimental results suggest that, with this fiber bundle and the polarization FWM-suppressing scheme, the signal-to-noise ratio of the CARS images was greatly enhanced through a combination of high collection efficiency of epi-CARS signals, isolation of excitation lasers, and suppression of FWM. Tissue imaging capability of the microendoscopy prototype was demonstrated by ex vivo imaging on mouse skin and lung tissues. This fiber bundle-based CARS microendoscopy prototype, with the polarization FWM-suppressing scheme, offers a promising platform for constructing efficient fiber-based CARS microendoscopes for label free intraoperative imaging applications.

  16. Imaging of lipids in microalgae with coherent anti-stokes Raman scattering microscopy.

    PubMed

    Cavonius, Lillie; Fink, Helen; Kiskis, Juris; Albers, Eva; Undeland, Ingrid; Enejder, Annika

    2015-03-01

    Microalgae have great prospects as a sustainable resource of lipids for refinement into nutraceuticals and biodiesel, which increases the need for detailed insights into their intracellular lipid synthesis/storage mechanisms. As an alternative strategy to solvent- and label-based lipid quantification techniques, we introduce time-gated coherent anti-Stokes Raman scattering (CARS) microscopy for monitoring lipid contents in living algae, despite strong autofluorescence from the chloroplasts, at approximately picogram and subcellular levels by probing inherent molecular vibrations. Intracellular lipid droplet synthesis was followed in Phaeodactylum tricornutum algae grown under (1) light/nutrient-replete (control [Ctrl]), (2) light-limited (LL), and (3) nitrogen-starved (NS) conditions. Good correlation (r(2) = 0.924) was found between lipid volume data yielded by CARS microscopy and total fatty acid content obtained from gas chromatography-mass spectrometry analysis. In Ctrl and LL cells, micron-sized lipid droplets were found to increase in number throughout the growth phases, particularly in the stationary phase. During more excessive lipid accumulation, as observed in NS cells, promising commercial harvest as biofuels and nutritional lipids, several micron-sized droplets were present already initially during cultivation, which then fused into a single giant droplet toward stationary phase alongside with new droplets emerging. CARS microspectroscopy further indicated lower lipid fluidity in NS cells than in Ctrl and LL cells, potentially due to higher fatty acid saturation. This agreed with the fatty acid profiles gathered by gas chromatography-mass spectrometry. CARS microscopy could thus provide quantitative and semiqualitative data at the single-cell level along with important insights into lipid-accumulating mechanisms, here revealing two different modes for normal and excessive lipid accumulation. PMID:25583924

  17. Imaging of Lipids in Microalgae with Coherent Anti-Stokes Raman Scattering Microscopy1[OPEN

    PubMed Central

    Cavonius, Lillie; Fink, Helen; Kiskis, Juris; Albers, Eva; Undeland, Ingrid; Enejder, Annika

    2015-01-01

    Microalgae have great prospects as a sustainable resource of lipids for refinement into nutraceuticals and biodiesel, which increases the need for detailed insights into their intracellular lipid synthesis/storage mechanisms. As an alternative strategy to solvent- and label-based lipid quantification techniques, we introduce time-gated coherent anti-Stokes Raman scattering (CARS) microscopy for monitoring lipid contents in living algae, despite strong autofluorescence from the chloroplasts, at approximately picogram and subcellular levels by probing inherent molecular vibrations. Intracellular lipid droplet synthesis was followed in Phaeodactylum tricornutum algae grown under (1) light/nutrient-replete (control [Ctrl]), (2) light-limited (LL), and (3) nitrogen-starved (NS) conditions. Good correlation (r2 = 0.924) was found between lipid volume data yielded by CARS microscopy and total fatty acid content obtained from gas chromatography-mass spectrometry analysis. In Ctrl and LL cells, micron-sized lipid droplets were found to increase in number throughout the growth phases, particularly in the stationary phase. During more excessive lipid accumulation, as observed in NS cells, promising commercial harvest as biofuels and nutritional lipids, several micron-sized droplets were present already initially during cultivation, which then fused into a single giant droplet toward stationary phase alongside with new droplets emerging. CARS microspectroscopy further indicated lower lipid fluidity in NS cells than in Ctrl and LL cells, potentially due to higher fatty acid saturation. This agreed with the fatty acid profiles gathered by gas chromatography-mass spectrometry. CARS microscopy could thus provide quantitative and semiqualitative data at the single-cell level along with important insights into lipid-accumulating mechanisms, here revealing two different modes for normal and excessive lipid accumulation. PMID:25583924

  18. Raman and coherent anti-Stokes Raman scattering microscopy studies of changes in lipid content and composition in hormone-treated breast and prostate cancer cells

    NASA Astrophysics Data System (ADS)

    Potcoava, Mariana C.; Futia, Gregory L.; Aughenbaugh, Jessica; Schlaepfer, Isabel R.; Gibson, Emily A.

    2014-11-01

    Increasing interest in the role of lipids in cancer cell proliferation and resistance to drug therapies has motivated the need to develop better tools for cellular lipid analysis. Quantification of lipids in cells is typically done by destructive chromatography protocols that do not provide spatial information on lipid distribution and prevent dynamic live cell studies. Methods that allow the analysis of lipid content in live cells are therefore of great importance. Using micro-Raman spectroscopy and coherent anti-Stokes Raman scattering (CARS) microscopy, we generated a lipid profile for breast (T47D, MDA-MB-231) and prostate (LNCaP, PC3) cancer cells upon exposure to medroxyprogesterone acetate (MPA) and synthetic androgen R1881. Combining Raman spectra with CARS imaging, we can study the process of hormone-mediated lipogenesis. Our results show that hormone-treated cancer cells T47D and LNCaP have an increased number and size of intracellular lipid droplets and higher degree of saturation than untreated cells. MDA-MB-231 and PC3 cancer cells showed no significant changes upon treatment. Principal component analysis with linear discriminant analysis of the Raman spectra was able to differentiate between cancer cells that were treated with MPA, R1881, and untreated.

  19. Raman and coherent anti-Stokes Raman scattering microscopy studies of changes in lipid content and composition in hormone-treated breast and prostate cancer cells

    PubMed Central

    Potcoava, Mariana C.; Futia, Gregory L.; Aughenbaugh, Jessica; Schlaepfer, Isabel R.; Gibson, Emily A.

    2014-01-01

    Abstract. Increasing interest in the role of lipids in cancer cell proliferation and resistance to drug therapies has motivated the need to develop better tools for cellular lipid analysis. Quantification of lipids in cells is typically done by destructive chromatography protocols that do not provide spatial information on lipid distribution and prevent dynamic live cell studies. Methods that allow the analysis of lipid content in live cells are therefore of great importance. Using micro-Raman spectroscopy and coherent anti-Stokes Raman scattering (CARS) microscopy, we generated a lipid profile for breast (T47D, MDA-MB-231) and prostate (LNCaP, PC3) cancer cells upon exposure to medroxyprogesterone acetate (MPA) and synthetic androgen R1881. Combining Raman spectra with CARS imaging, we can study the process of hormone-mediated lipogenesis. Our results show that hormone-treated cancer cells T47D and LNCaP have an increased number and size of intracellular lipid droplets and higher degree of saturation than untreated cells. MDA-MB-231 and PC3 cancer cells showed no significant changes upon treatment. Principal component analysis with linear discriminant analysis of the Raman spectra was able to differentiate between cancer cells that were treated with MPA, R1881, and untreated. PMID:24933682

  20. Bandwidth optimization of femtosecond pure-rotational coherent anti-Stokes Raman scattering by pump/Stokes spectral focusing.

    DOE PAGESBeta

    Kearney, Sean Patrick

    2014-07-01

    A simple spectral focusing scheme for bandwidth optimization of gas-phase rotational coherent anti-Stokes Raman scattering (CARS) spectra is presented. The method is useful when femtosecond pump/Stokes preparation of the Raman coherence is utilized. The approach is of practical utility when working with laser pulses that are not strictly transform limited, or when windows or other sources of pulse chirp may be present in the experiment. A delay between the femtosecond preparation pulses is introduced to shift the maximum Raman preparation away from zero frequency and toward the Stokes or anti-Stokes side of the spectrum with no loss in total preparationmore » bandwidth. Shifts of 100 cm-1 or more are attainable and allow for enhanced detection of high-energy (150-300 cm-1) rotational Raman transitions at near transform-limited optimum sensitivity. A simple theoretical treatment for the case of identical pump and Stokes pulses with linear frequency chirp is presented. The approach is then demonstrated experimentally for typical levels of transform-limited laser performance obtained our laboratory with nonresonant CARS in argon and Raman-resonant spectra from a lean H2/air flat flame.« less

  1. Bandwidth optimization of femtosecond pure-rotational coherent anti-Stokes Raman scattering by pump/Stokes spectral focusing.

    SciTech Connect

    Kearney, Sean Patrick

    2014-07-01

    A simple spectral focusing scheme for bandwidth optimization of gas-phase rotational coherent anti-Stokes Raman scattering (CARS) spectra is presented. The method is useful when femtosecond pump/Stokes preparation of the Raman coherence is utilized. The approach is of practical utility when working with laser pulses that are not strictly transform limited, or when windows or other sources of pulse chirp may be present in the experiment. A delay between the femtosecond preparation pulses is introduced to shift the maximum Raman preparation away from zero frequency and toward the Stokes or anti-Stokes side of the spectrum with no loss in total preparation bandwidth. Shifts of 100 cm-1 or more are attainable and allow for enhanced detection of high-energy (150-300 cm-1) rotational Raman transitions at near transform-limited optimum sensitivity. A simple theoretical treatment for the case of identical pump and Stokes pulses with linear frequency chirp is presented. The approach is then demonstrated experimentally for typical levels of transform-limited laser performance obtained our laboratory with nonresonant CARS in argon and Raman-resonant spectra from a lean H2/air flat flame.

  2. Sum frequency generation and coherent anti-Stokes Raman spectroscopic studies on plasma-treated plasticized polyvinyl chloride films.

    PubMed

    Hankett, Jeanne M; Zhang, Chi; Chen, Zhan

    2012-03-13

    Polyvinyl chloride (PVC) is a widely used polymer to which various phthalates are extensively applied as plasticizers. PVC materials are often treated with plasma to vary the hydrophobicity or for cleaning purposes, but little is known of the nature of the surface molecular structures after treatment. This research characterizes molecular surface structures of PVC and bis-2-ethylhexyl phthalate (DEHP)-plasticized PVC films in air before annealing, after annealing, and after exposure to air-generated glow discharge plasma using sum frequency generation (SFG) vibrational spectroscopy. In addition, we compare the vibrational molecular signatures on the surfaces of PVC with DEHP (at a variety of percent loadings) to those of the bulk detected using coherent anti-Stokes Raman scattering (CARS). X-ray photoelectron spectroscopy (XPS) and contact angle measurements have been used to analyze PVC surfaces to supplement SFG data. Our results indicate that DEHP was found on the surfaces of PVC films even at low weight percentages (5 wt %) and that DEHP segregates on surfaces after annealing. The treatment of these films with glow discharge plasma resulted in surface-sensitive reactions involving the removal of chlorine atoms, the addition of oxygen atoms, and C-H bond rearrangement. CARS data demonstrate that the bulk of our films remained undisturbed during the plasma treatment. For the first time, we probed the molecular structure of the surface and the bulk of a PVC material using combined SFG and CARS studies on the same sample in exactly the same environment. In addition, the methodology used in this research can be applied to characterize various plasticizers in a wide variety of polymer systems to understand their surface and bulk structures before and after systematic applications of heat, plasma, or other treatments. PMID:22309397

  3. Analysis of aquaporin-mediated diffusional water permeability by coherent anti-stokes Raman scattering microscopy.

    PubMed

    Ibata, Keiji; Takimoto, Shinichi; Morisaku, Toshinori; Miyawaki, Atsushi; Yasui, Masato

    2011-11-01

    Water can pass through biological membranes via two pathways: simple diffusion through the lipid bilayer, or water-selective facilitated diffusion through aquaporins (AQPs). Although AQPs play an important role in osmotic water permeability (P(f)), the role of AQPs in diffusional water permeability remains unclear because of the difficulty of measuring diffusional water permeability (P(d)). Here, we report an accurate and instantaneous method for measuring the P(d) of a single HeLa S3 cell using coherent anti-Stokes Raman scattering (CARS) microscopy with a quick perfusion device for H(2)O/D(2)O exchange. Ultra-high-speed line-scan CARS images were obtained every 0.488 ms. The average decay time constant of CARS intensities (τ(CARS)) for the external solution H(2)O/D(2)O exchange was 16.1 ms, whereas the intracellular H(2)O/D(2)O exchange was 100.7 ± 19.6 ms. To evaluate the roles of AQP in diffusional water permeability, AQP4 fused with enhanced green fluorescent protein (AQP4-EGFP) was transiently expressed in HeLa S3 cells. The average τ(CARS) for the intracellular H(2)O/D(2)O exchange in the AQP4-EGFP-HeLa S3 cells was 43.1 ± 15.8 ms. We also assessed the cell volume and the cell surface area to calculate P(d). The average P(d) values for the AQP4-EGFP-HeLa S3 cells and the control EGFP-HeLa S3 cells were 2.7 ± 1.0 × 10(-3) and 8.3 ± 2.6 × 10(-4) cm/s, respectively. AQP4-mediated water diffusion was independent of the temperature but was dependent on the expression level of the protein at the plasma membrane. These results suggest the possibility of using CARS imaging to investigate the hydrodynamics of single mammalian cells as well as the regulation of AQPs. PMID:22067168

  4. Dynamical rate theory of enzymatic reactions and triple-resonant coherent anti-Stokes Raman scattering microspectroscopy

    NASA Astrophysics Data System (ADS)

    Min, Wei

    Chapters 2-7 focus on physical enzymology. Despite its long history, recent single-molecule spectroscopy, among many others techniques, has generated new quantitative data that reveal unobserved features of protein dynamics and enzyme catalysis at unprecedented levels. Much of these are beyond the classic framework of transition state theory and Michalis-Menten (MM) enzyme kinetics. Due to the complexity of the problem, theoretical developments in this area have much lagged behind experiments. After an initial experimental characterization on single-molecule protein conformational fluctuations, we then develop a dynamical rate theory for enzyme catalyzed chemical reactions, from a statistical mechanics approach. Towards this goal, we formulate a two-dimensional (2D) multi-surface free energy description of the entire catalytic process that explicitly combines the concept of "fluctuating enzymes" with the MM enzyme kinetics. The outcome of this framework has two folds. On the rate theory side, going much beyond transition state theory, it connects conformational fluctuations to catalysis, allows for the interplay between energetics (e.g. Haldane's stain energy) and dynamics (e.g. Koshland's induced fit), and predicts the time dependence of single-enzyme catalysis. On the enzyme kinetics side, it gives mechanistic and unified understanding of MM and non-MM (both positive and negative cooperativity) kinetics of monomeric enzymes, in term of non-equilibrium steady state cycle on the 2D free energy surface. Chapters 8-11 present the principle and application of a new ultra-sensitive nonlinear optical microspectroscopy, femtosecond (fs) triple-resonant coherent anti-Stokes Raman scattering (CARS), in which the amplitude and phase of input fs laser pulses are optimally shaped to be in triple resonant with the molecular electronic and vibrational transitions to generate a coherent nonlinear signal beam at a new color with a highest possible efficiency. This technique

  5. Super-Spatial- and -Spectral-Resolution in Vibrational Imaging via Saturated Coherent Anti-Stokes Raman Scattering

    NASA Astrophysics Data System (ADS)

    Yonemaru, Yasuo; Palonpon, Almar F.; Kawano, Shogo; Smith, Nicholas I.; Kawata, Satoshi; Fujita, Katsumasa

    2015-07-01

    We demonstrate a vibrational microscopy technique with subdiffraction spatial resolution by the use of saturation of coherent anti-Stokes Raman scattering (CARS). The saturated CARS signals effectively produce a reduced point-spread function at harmonic frequencies, which is extracted by temporal modulation of the pump beam and demodulation of the CARS signal. An increase in spectral resolution and suppression of the nonresonant background signal accompany the spatial- resolution enhancement. Our simple, enhanced CARS technique promises to be useful in studying molecules in gas and liquid phases as well as soft condensed-matter systems.

  6. Rotational coherence imaging and control for CN molecules through time-frequency resolved coherent anti-Stokes Raman scattering.

    PubMed

    Lindgren, Johan; Hulkko, Eero; Pettersson, Mika; Kiljunen, Toni

    2011-12-14

    Numerical wave packet simulations are performed for studying coherent anti-Stokes Raman scattering (CARS) for CN radicals. Electronic coherence is created by femtosecond laser pulses between the X(2)Σ and B(2)Σ states. Due to the large energy separation of vibrational states, the wave packets are superpositions of rotational states only. This allows for a specially detailed inspection of the second- and third-order coherences by a two-dimensional imaging approach. We present the time-frequency domain images to illustrate the intra- and intermolecular interferences, and discuss the procedure to rationally control and experimentally detect the interferograms in solid Xe environment. PMID:22168710

  7. Coherent anti-Stokes Raman scattering microspectroscopic kinetic study of fast hydrogen bond formation in microfluidic devices.

    PubMed

    Oshovsky, Gennady V; Rago, Gianluca; Day, James P R; Soudijn, Maarten L; Rock, William; Parekh, Sapun H; Ciancaleoni, Gianluca; Reek, Joost N H; Bonn, Mischa

    2013-10-01

    The kinetics of a key noncovalent, hydrogen bonding interaction was studied in situ using coherent anti-stokes Raman scattering (CARS) microspectroscopy in a microfluidic device. The association of model compounds, pyridine and hexafluoroisopropanol, was quantitatively monitored with submicrometer resolution. Lower limits for the very high formation and dissociation rate constants of the model 1:1 pyridine-hexafluoroisopropanol hydrogen bonded complex in dichloromethane-d2 were determined to be k1 > 10(5) M(-1)s(-1) and k-1 > 333.3 s(-1), respectively. PMID:23987583

  8. Comparative Study of Breast Normal and Cancer Cells Using Coherent Anti-Stokes Raman Scattering Microspectroscopy Imaging

    NASA Astrophysics Data System (ADS)

    Lee, Jang Hyuk; Cho, Eun Hee; Shin, Sang-Mo; Oh, Myoung-kyu; Ko, Do-Kyeong

    2012-08-01

    A coherent anti-Stokes Raman scattering (CARS) microspectroscopy imaging system was developed using a femtosecond laser and a photonic crystal fiber (PCF). We separated resonant and non-resonant CARS signals in the time domain by the chirp of the PCF, and applied this system to compare live human breast normal and cancer cells. The CARS image and spectrum at C-H stretch vibration in lipid droplets could subsequently be used to differentiate cancer cells from normal cells, thereby confirming the potential of the CARS microspectroscopy imaging system as a diagnostic tool that allows the high-sensitivity, high-resolution, and fast detection of breast cancer.

  9. Spatially dependent Rabi oscillations: An approach to sub-diffraction-limited coherent anti-Stokes Raman-scattering microscopy

    SciTech Connect

    Beeker, Willem P.; Lee, Chris J.; Boller, Klaus-Jochen; Gross, Petra; Cleff, Carsten; Fallnich, Carsten; Offerhaus, Herman L.; Herek, Jennifer L.

    2010-01-15

    We present a theoretical investigation of coherent anti-Stokes Raman scattering (CARS) that is modulated by periodically depleting the ground-state population through Rabi oscillations driven by an additional control laser. We find that such a process generates optical sidebands in the CARS spectrum and that the frequency of the sidebands depends on the intensity of the control laser light field. We show that analyzing the sideband frequency upon scanning the beams across the sample allows one to spatially resolve emitter positions where a spatial resolution of 65 nm, which is well below the diffraction limit, can be obtained.

  10. Dual-pump vibrational/rotational femtosecond/picosecond coherent anti-Stokes Raman scattering temperature and species measurements.

    PubMed

    Dedic, Chloe E; Miller, Joseph D; Meyer, Terrence R

    2014-12-01

    A method for simultaneous ro-vibrational and pure-rotational hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps CARS) is presented for multi-species detection and improved temperature sensitivity from room temperature to flame conditions. N₂/CH₄ vibrational and N₂/O₂/H₂ rotational Raman coherences are excited simultaneously using fs pump pulses at 660 and 798 nm, respectively, and a common fs Stokes pulse at 798 nm. A fourth narrowband 798 nm ps pulse probes all coherence states at a time delay that minimizes nonresonant background and the effects of collisions. The transition strength is concentration dependent, while the distribution among observed transitions is related to temperature through the Boltzmann distribution. The broadband excitation pulses and multiplexed signal are demonstrated for accurate thermometry from 298 to 2400 K and concentration measurements of four key combustion species. PMID:25490633

  11. Chemical imaging with frequency modulation coherent anti-Stokes Raman scattering microscopy at the vibrational fingerprint region.

    PubMed

    Chen, Bi-Chang; Sung, Jiha; Lim, Sang-Hyun

    2010-12-23

    We present a new coherent anti-Stokes Raman scattering (CARS) method that can perform background-free microscopy and microspectroscopy at the vibrational fingerprint region. Chirped broad-band pulses from a single Ti:sapphire laser generate CARS signals over 800-1700 cm(-1) with a spectral resolution of 20 cm(-1). Fast modulation of the time delay between the pump and Stokes pulses coupled with lock-in signal detection not only removes the nonresonant background but also produces Raman-like CARS signals. Chemical imaging and microspectroscopy are demonstrated with various samples such as edible oils, lipid membranes, skin tissue, and plant cell walls. Systematic studies of the signal generation mechanism and several fundamental aspects are discussed. PMID:21126030

  12. Discrimination of chemical warfare simulants via multiplex coherent anti-Stokes Raman scattering and multivariate statistical analysis

    NASA Astrophysics Data System (ADS)

    Brady, John J.; Farrell, Mikella E.; Pellegrino, Paul M.

    2014-02-01

    Multiplex coherent anti-Stokes Raman scattering (MCARS) is used to detect several chemical warfare simulants, such as dimethyl methylphosphonate and 2-chloroethyl ethyl sulfide, with high specificity. The spectral bandwidth of the femtosecond laser pulse used in these studies is sufficient to coherently and simultaneously drive all the vibrational modes in the molecule of interest. Evidence shows that MCARS is capable of overcoming common sensitivity limitations of spontaneous Raman scattering, thus allowing for the detection of the target material in milliseconds with standard, uncooled universal serial bus spectrometers as opposed to seconds with cooled, intensified CCD-based spectrometers. In addition, the obtained MCARS spectrum of the investigated sample provides multiple unique signatures. These signatures are used in an off-line multivariate statistical analysis allowing for the material's discrimination with high fidelity.

  13. Increasing the imaging depth of coherent anti-Stokes Raman scattering microscopy with a miniature microscope objective

    NASA Astrophysics Data System (ADS)

    Wang, Haifeng; Huff, Terry B.; Fu, Yan; Jia, Kevin Y.; Cheng, Ji-Xin

    2007-08-01

    A miniature objective lens with a tip diameter of 1.3 mm was used for extending the penetration depth of coherent anti-Stokes Raman scattering (CARS) microscopy. Its axial and lateral focal widths were determined to be 11.4 and 0.86 μm, respectively, by two-photon excitation fluorescence imaging of 200 nm beads at a 735 nm excitation wavelength. By inserting the lens tip into a soft gel sample, CARS images of 2 μm polystyrene beads 5 mm deep from the surface were acquired. The miniature objective was applied to CARS imaging of rat spinal cord white matter with a minimal requirement for surgery.

  14. Measurement of vibrational populations in low-pressure hydrogen plasma by coherent anti-Stokes Raman scattering

    NASA Astrophysics Data System (ADS)

    Pealat, M.; Taran, J. P. E.; Taillet, J.; Bacal, M.; Bruneteau, A. M.

    1981-04-01

    Vibrational populations in a low-pressure H2 plasma have been measured by coherent anti-Stokes Raman scattering (CARS). The plasma generator is described, and some particulars of the optical arrangement are given. The CARS system is a commercial spectrometer, whose original optical system has been slightly modified for this study, by eliminating the Polarex arrangement for the YAG laser oscillator and by adding a YAG amplifier stage. This has resulted in improved beam quality and enhanced peak power. For an electron density of 2 x 10 to the 11th cm to the 0.001 and a total pressure of 0.13 m bar, the rotational temperature was found to be 475 K. The populations of the vibrational states v equals 0, 1, and 2 have also been measured. Their distribution is non-Boltzmann. The influence of pressure and discharge parameters is discussed.

  15. Nonlinear optical interference of two successive coherent anti-Stokes Raman scattering signals for biological imaging applications.

    PubMed

    Lee, Eun Seong; Lee, Jae Yong; Yoo, Yong Shim

    2007-01-01

    The nonlinear optical interference of two successively generated coherent anti-Stokes Raman scattering (CARS) signals from two different samples placed in series is demonstrated for the imaging performance, in which a collinear phase matching geometry is used. The relative phase of two CARS signals is controlled by a phase-shifting unit made of dispersive glass materials of which the thickness can be precisely varied. The clear interference fringes are observed as the thickness of the phase-shifting unit changes. The interference effect is then utilized to achieve a better quality CARS image of a biological tissue taken from a mouse skin. Placing the tissue in the second sample position and performing raster scans of the laser beams on it, we can acquire a CARS image of higher contrast compared to the normal image obtained without interferometric implementation. PMID:17477725

  16. Texture analysis and classification in coherent anti-Stokes Raman scattering (CARS) microscopy images for automated detection of skin cancer.

    PubMed

    Legesse, Fisseha Bekele; Medyukhina, Anna; Heuke, Sandro; Popp, Jürgen

    2015-07-01

    Coherent anti-Stokes Raman scattering (CARS) microscopy is a powerful tool for fast label-free tissue imaging, which is promising for early medical diagnostics. To facilitate the diagnostic process, automatic image analysis algorithms, which are capable of extracting relevant features from the image content, are needed. In this contribution we perform an automated classification of healthy and tumor areas in CARS images of basal cell carcinoma (BCC) skin samples. The classification is based on extraction of texture features from image regions and subsequent classification of these regions into healthy and cancerous with a perceptron algorithm. The developed approach is capable of an accurate classification of texture types with high sensitivity and specificity, which is an important step towards an automated tumor detection procedure. PMID:25797604

  17. Longitudinal in vivo coherent anti-Stokes Raman scattering imaging of demyelination and remyelination in injured spinal cord

    NASA Astrophysics Data System (ADS)

    Shi, Yunzhou; Zhang, Delong; Huff, Terry B.; Wang, Xiaofei; Shi, Riyi; Xu, Xiao-Ming; Cheng, Ji-Xin

    2011-10-01

    In vivo imaging of white matter is important for the mechanistic understanding of demyelination and evaluation of remyelination therapies. Although white matter can be visualized by a strong coherent anti-Stokes Raman scattering (CARS) signal from axonal myelin, in vivo repetitive CARS imaging of the spinal cord remains a challenge due to complexities induced by the laminectomy surgery. We present a careful experimental design that enabled longitudinal CARS imaging of de- and remyelination at single axon level in live rats. In vivo CARS imaging of secretory phospholipase A2 induced myelin vesiculation, macrophage uptake of myelin debris, and spontaneous remyelination by Schwann cells are sequentially monitored over a 3 week period. Longitudinal visualization of de- and remyelination at a single axon level provides a novel platform for rational design of therapies aimed at promoting myelin plasticity and repair.

  18. In vivo histology: optical biopsies with chemical contrast using clinical multiphoton/coherent anti-Stokes Raman scattering tomography

    NASA Astrophysics Data System (ADS)

    Weinigel, M.; Breunig, H. G.; Kellner-Höfer, M.; Bückle, R.; Darvin, M. E.; Klemp, M.; Lademann, J.; König, K.

    2014-05-01

    The majority of existing coherent anti-Stokes Raman scattering (CARS) imaging systems are still huge and complicated laboratory systems and neither compact nor user-friendly nor mobile medically certified CARS systems. We have developed a new flexible multiphoton/CARS tomograph for imaging in a clinical environment. The system offers exceptional 360° flexibility with a very stable setup and enables label free ‘in vivo histology’ with chemical contrast within seconds. It can be completely operated by briefly trained non-laser experts. The imaging capability and flexibility of the novel in vivo tomograph are shown on optical biopsies with subcellular resolution and chemical contrast of patients suffering from psoriasis and squamous cell carcinoma.

  19. Observation of anti-Stokes-stimulated Raman scattering and two-photon emission in lithium and sodium vapors

    NASA Astrophysics Data System (ADS)

    Chen, F. Z.; Wu, C. Y. Robert; Yih, T. S.; Wu, H. H.; Hsu, Y. C.; Lin, K. C.

    1988-10-01

    We have observed anti-Stokes-stimulated Raman scattering (ASRS) and two-photon emission (TPE) in Li and Na metal vapors. We found that the TPE can be generated from most of the excited even-parity states of both atoms but not ASRS. In the present work, the ``pump laser lines'' which stimulate the ASRS and TPE are those optically-pumped stimulated emissions (OPSE) generated in the same alkali metal vapor. Since ASRS and TPE processes take place from the same metastable state, strong competitions between both processes are expected. Enhanced outputs due to the presence of a resonant intermediate state in the ASRS and TPE processes have also been observed.

  20. Wavelength conversion of quadrupled Nd:YAG laser radiation to the vacuum ultraviolet by anti-stokes stimulated Raman scattering

    NASA Astrophysics Data System (ADS)

    Moriwaki, Hiroki; Wada, Satoshi; Tashiro, Hideo; Toyoda, Koichi; Kasai, Akinari; Nakamura, Akira

    1993-08-01

    The observations from the beam property measurements of anti-Stokes (AS) pulses produced form AS Raman scattering (ASRS) using a quadrupled Nd:YAG laser were presented. The beam profiles of each AS wave were photographically examined. The beam pattern did not always exhibit a ring shape, but became tophatlike shaped or Gaussian-like shaped, provided the hydrogen pressure was kept lower than 0.39 MPa. The beam divergence of the AS ring radiation was elucidated using a model in which the wave front of the pump beam was considered as a plane within the Rayleigh region. The output energies of AS beams up to the ninth order were also estimated. The well-defined coherent vuv radiation produced by a tabletop ASRS system can be a fitting source for different application such as ablation of polymer films.

  1. Excitation profile of coherent anti-Stokes Raman scattering from the MnO - 4 ion doped in a KClO4 crystal at low temperature

    NASA Astrophysics Data System (ADS)

    Leuchs, M.; Kiefer, W.

    1993-11-01

    We have performed polarized resonance coherent anti-Stokes Raman experiments on the permanganate ion doped in potassium perchlorate single crystals at temperature T=15 K. At this temperature the m (Cs) site splitting of the excited degenerate 1T2-electronic level of the permanganate ion and the vibronic structure are well resolved. We report on the A'-ν1 coherent anti-Stokes Raman excitation profile which shows a strong dependence on the frequency of the pump laser. The simulation of the experimental results is performed by using the transform theory, which enables one to calculate the resonance Raman excitation profile solely from the measured absorption spectrum. According to the well known relation between the third-order nonlinear susceptibility and the Raman polarizability the coherent anti-Stokes excitation profile is given by a simple product of two Raman excitation profiles which are shifted relative to each other. The linear and the quadratic electron-phonon coupling as well as the influence of non-Condon terms were taken into account. Since the transform theory is mode selective in case there are no mode mixing effects the results derived from the description of the Raman excitation profiles and the coherent anti-Stokes excitation profiles are more definite. For this purpose one only needs the model parameters of the mode of interest. The simulation of the A'-ν1 coherent anti-Stokes profile shows that a small amount of non-Condon coupling yields to a better agreement with the experiment.

  2. Method and system to measure temperature of gases using coherent anti-stokes doppler spectroscopy

    DOEpatents

    Rhodes, Mark

    2013-12-17

    A method of measuring a temperature of a noble gas in a chamber includes providing the noble gas in the chamber. The noble gas is characterized by a pressure and a temperature. The method also includes directing a first laser beam into the chamber and directing a second laser beam into the chamber. The first laser beam is characterized by a first frequency and the second laser beam is characterized by a second frequency. The method further includes converting at least a portion of the first laser beam and the second laser beam into a coherent anti-Stokes beam, measuring a Doppler broadening of the coherent anti-Stokes beam, and computing the temperature using the Doppler broadening.

  3. Picosecond coherent anti-Stokes Raman scattering (CARS) study of vibrational dephasing of carbon disulfide and benzene in solution

    NASA Technical Reports Server (NTRS)

    Perry, Joseph W.; Woodward, Anne M.; Stephenson, John C.

    1986-01-01

    The vibrational dephasing of the 656/cm mode (nu1, a1g) of CS2 and the 991/cm mode (nu2, a1g) of benzene have been studied as a function of concentration in mixtures with a number of solvents using a ps time-resolved CARS technique. This technique employs two tunable synchronously-pumped mode-locked dye lasers in a stimulated Raman pump, coherent anti-Stokes Raman probe time-resolved experiment. Results are obtained for CS2 in carbon tetrachloride, benzene, nitrobenzene, and ethanol and for benzene nu2 in CS2. The dephasing rates of CS2 nu1 increase on dilution with the polar solvents and decrease or remain constant on dilution with the nonpolar solvents. The CS2/benzene solutions show a contrasting behavior, with the CS2 nu1 dephasing rate being nearly independent of concentration whereas the benzene nu2 dephasing rate decreases on dilution. These results are compared to theoretical models for vibrational dephasing of polyatomic molecules in solution.

  4. Red-shifted solitons for coherent anti-Stokes Raman scattering microspectroscopy in a polarization-maintaining photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Yuan, Jinhui; Sang, Xinzhu; Wu, Qiang; Zhou, Guiyao; Li, Feng; Yu, Chongxiu; Wang, Kuiru; Yan, Binbin; Han, Ying; Tam, Hwa Yaw; Wai, Ping-kong Alexander

    2015-05-01

    An alternative light source for coherent anti-Stokes Raman scattering (CARS) microspectroscopy based on red-shifted solitons in a polarization-maintaining photonic crystal fiber (PM-PCF) is experimentally demonstrated. By coupling femtosecond pulses into the anomalous dispersion region of the fundamental mode of a PM-PCF along the slow and fast axes, the red-shifted solitons generated can be used as the Stokes beams when the pump pulses are chosen as the pump beams. Through the process of red-shift, the frequency differences of the pump-Stokes beams are tunable in the ranges of 0 to 4068 cm-1 and 0 to 4594 cm-1, respectively. Moreover, because of the well maintained polarization states of the pump and Stokes beams and the high output powers of the solitons, CARS microspectroscopy using the proposed source will have a high signal-to-noise ratio and short data acquisition time. CARS microspectroscopy based on the proposed all-fiber light source can be used for studying a wide range of vibrational Raman spectra.

  5. Hyperspectral coherent anti-Stokes Raman scattering microscopy for in situ analysis of solid-state crystal polymorphs

    NASA Astrophysics Data System (ADS)

    Garbacik, E. T.; Fussell, A. L.; Güres, S.; Korterik, J. P.; Otto, C.; Herek, J. L.; Offerhaus, H. L.

    2013-02-01

    Hyperspectral coherent anti-Stokes Raman scattering (CARS) microscopy is quickly becoming a prominent imaging modality because of its many advantages over the traditional paradigm of multispectral CARS. In particular, recording a significant portion of the vibrational spectrum at each spatial pixel allows image-wide spectral analysis at much higher rates than can be achieved with spontaneous Raman. We recently developed a hyperspectral CARS method, the driving principle behind which is the fast acquisition and display of a hyperspectral datacube as a set of intuitive images wherein each material in a sample appears with a unique trio of colors. Here we use this system to image and analyze two types of polymorphic samples: the pseudopolymorphic hydration of theophylline, and the packing polymorphs of the sugar alcohol mannitol. In addition to these solid-state form modifications we have observed spectral variations of crystalline mannitol and diprophylline as functions of their orientations relative to the optical fields. We use that information to visualize the distributions of these compounds in a pharmaceutical solid oral dosage form.

  6. Probe-pulse optimization for nonresonant suppression in hybrid fs/ps coherent anti-Stokes Raman scattering at high temperature.

    PubMed

    Miller, Joseph D; Slipchenko, Mikhail N; Meyer, Terrence R

    2011-07-01

    Hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps CARS) offers accurate thermometry at kHz rates for combustion diagnostics. In high-temperature flames, selection of probe-pulse characteristics is key to simultaneously optimizing signal-to-nonresonant-background ratio, signal strength, and spectral resolution. We demonstrate a simple method for enhancing signal-to-nonresonant-background ratio by using a narrowband Lorentzian filter to generate a time-asymmetric probe pulse with full-width-half-maximum (FWHM) pulse width of only 240 fs. This allows detection within just 310 fs after the Raman excitation for eliminating nonresonant background while retaining 45% of the resonant signal at 2000 K. The narrow linewidth is comparable to that of a time-symmetric sinc2 probe pulse with a pulse width of ~2.4 ps generated with a conventional 4-f pulse shaper. This allows nonresonant-background-free, frequency-domain vibrational spectroscopy at high temperature, as verified using comparisons to a time-dependent theoretical fs/ps CARS model. PMID:21747487

  7. Development of Combined Dual-Pump Vibrational and Pure-Rotational Coherent Anti-Stokes Raman Scattering Technique.

    NASA Astrophysics Data System (ADS)

    Satija, Aman; Lucht, Robert P.

    2015-06-01

    Coherent anti-Stokes Raman scattering is a parametric, four-wave mixing process. CARS, as a diagnostic technique, has been used extensively for obtaining accurate temperature and species concentration information in non-reacting and reacting flows. Dual-pump vibrational CARS (DPVCARS) can provide quantitative temperature and concentration information on multiple species in the probe volume. Mole-fraction information on molecules such as N2, O2, H2 and CO2 have been obtained in flames with peak temperature in excess of 2000 K. Although DPVCARS provides high accuracy at higher temperatures it has low sensitivity at lower temperatures (below 800 K). Typically, pure-rotational CARS (PRCARS) provides excellent sensitivity and precision at lower temperatures. We have combined DPVCARS and two-beam PRCARS into a single system which employs three laser beams at different wavelengths. The accuracy and precision of the new combined CARS system has been characterized in laminar flames. The system's single-shot precision is better than 5.5 % between 295-2200 K, indicating its suitability for diagnostics in turbulent flames. The new system has been applied towards understanding flame structure of CH4/H2/air laminar flames, stabilized in a counter-flow burner. Here, we present results detailing the development and application of the new combined CARS technique.

  8. Effects of phase and coupling between the vibrational modes on selective excitation in coherent anti-Stokes Raman scattering microscopy

    SciTech Connect

    Patel, Vishesha; Malinovsky, Vladimir S.; Malinovskaya, Svetlana

    2010-06-15

    Coherent anti-Stokes Raman scattering (CARS) microscopy has been a major tool of investigation of biological structures as it contains the vibrational signature of molecules. A quantum control method based on chirped pulse adiabatic passage was recently proposed for selective excitation of a predetermined vibrational mode in CARS microscopy [Malinovskaya and Malinovsky, Opt. Lett. 32, 707 (2007)]. The method utilizes the chirp sign variation at the peak pulse amplitude and gives a robust adiabatic excitation of the desired vibrational mode. Using this method, we investigate the impact of coupling between vibrational modes in molecules on controllability of excitation of the CARS signal. We analyze two models of two coupled two-level systems (TLSs) having slightly different transitional frequencies. The first model, featuring degenerate ground states of the TLSs, gives robust adiabatic excitation and maximum coherence in the resonant TLS for positive value of the chirp. In the second model, implying nondegenerate ground states in the TLSs, a population distribution is observed in both TLSs, resulting in a lack of selectivity of excitation and low coherence. It is shown that the relative phase and coupling between the TLSs play an important role in optimizing coherence in the desired vibrational mode and suppressing unwanted transitions in CARS microscopy.

  9. Ex vivo and in vivo imaging of myelin fibers in mouse brain by coherent anti-Stokes Raman scattering microscopy

    PubMed Central

    Fu, Yan; Huff, T. Brandon; Wang, Han-Wei; Wang, Haifeng; Cheng, Ji-Xin

    2009-01-01

    Coherent anti-Stokes Raman scattering (CARS) microscopy was applied to image myelinated fibers in different regions of a mouse brain. The CARS signal from the CH2 symmetric stretching vibration allows label-free imaging of myelin sheath with 3D sub-micron resolution. Compared with two-photon excited fluorescence imaging with lipophilic dye labeling, CARS microscopy provides sharper contrast and avoids photobleaching. The CARS signal exhibits excitation polarization dependence which can be eliminated by reconstruction of two complementary images with perpendicular excitation polarizations. The capability of imaging myelinated fibers without exogenous labeling was used to map the whole brain white matter in brain slices and to analyze the microstructural anatomy of brain axons. Quantitative information about fiber volume%, myelin density, and fiber orientations was derived. Combining CARS with two-photon excited fluorescence allowed multimodal imaging of myelinated axons and other cells. Furthermore, in vivo CARS imaging on an upright microscope clearly identified fiber bundles in brain subcortex white matter. These advances open up new opportunities for the study of brain connectivity and neurological disorders. PMID:19030027

  10. Coherent anti-Stokes Raman scattering microscopy imaging with suppression of four-wave mixing in optical fibers.

    PubMed

    Wang, Zhiyong; Gao, Liang; Luo, Pengfei; Yang, Yaliang; Hammoudi, Ahmad A; Wong, Kelvin K; Wong, Stephen T C

    2011-04-25

    We demonstrated an optical fiber delivered coherent anti-Stokes Raman scattering (CARS) microscopy imaging system with a polarization-based mechanism for suppression of four-wave mixing (FWM) signals in delivery fiber. Polarization maintaining fibers (PMF) were used as the delivery fiber to ensure stability of the state of polarization (SOP) of lasers. The pump and Stokes waves were coupled into PMFs at orthogonal SOPs along the slow and fast axes of PMFs, respectively, resulting in a significant reduction of FWM signals generated in the fiber. At the output end of PMFs, a dual-wavelength waveplate was used to realign the SOPs of the two waves into identical SOPs prior to their entrance into the CARS microscope. Therefore, it allows the pump and Stokes waves with identical SOPs to excite samples at highest excitation efficiency. Our experimental results showed that this polarization-based FWM-suppressing mechanism can dramatically reduce FWM signals generated in PMFs up to approximately 99%. Meanwhile, the PMF-delivered CARS microscopy system with this mechanism can still produce high-quality CARS images. Consequently, our PMF-delivered CARS microscopy imaging system with the polarization-based FWM-suppressing mechanism potentially offers a new strategy for building fiber-based CARS endoscopes with effective suppression of FWM background noises. PMID:21643045

  11. Dual/differential coherent anti-Stokes Raman scattering module for multiphoton microscopes with a femtosecond Ti:sapphire oscillator.

    PubMed

    Li, Bei; Borri, Paola; Langbein, Wolfgang

    2013-06-01

    In the last decade, coherent anti-Stokes Raman scattering (CARS) microscopy has emerged as a powerful multiphoton imaging technique offering label-free chemical sensitivity and high three-dimensional resolution. However, its widespread application in the life sciences has been hampered by the use of costly pulsed lasers, the existence of a nonresonant background requiring involved technical solutions for its efficient suppression, and the limited acquisition speed of multiplex techniques addressing several vibrational resonances, if improved chemical specificity is needed. We have recently reported a differential CARS technique (D-CARS), which simultaneously measures two vibrational frequencies, enhancing the chemical selectivity and sensitivity without introducing costly hardware, while maintaining fast acquisition. In this study, we demonstrate a compact, fully automated, cost-effective module, which integrates on hardware and software level with a commercial multiphoton microscope based on a single 100 fs Ti:Sapphire oscillator and enables D-CARS microscopy in a user-friendly format for applications in the life sciences. PMID:23733020

  12. Dual/differential coherent anti-Stokes Raman scattering module for multiphoton microscopes with a femtosecond Ti:sapphire oscillator

    NASA Astrophysics Data System (ADS)

    Li, Bei; Borri, Paola; Langbein, Wolfgang

    2013-06-01

    In the last decade, coherent anti-Stokes Raman scattering (CARS) microscopy has emerged as a powerful multiphoton imaging technique offering label-free chemical sensitivity and high three-dimensional resolution. However, its widespread application in the life sciences has been hampered by the use of costly pulsed lasers, the existence of a nonresonant background requiring involved technical solutions for its efficient suppression, and the limited acquisition speed of multiplex techniques addressing several vibrational resonances, if improved chemical specificity is needed. We have recently reported a differential CARS technique (D-CARS), which simultaneously measures two vibrational frequencies, enhancing the chemical selectivity and sensitivity without introducing costly hardware, while maintaining fast acquisition. In this study, we demonstrate a compact, fully automated, cost-effective module, which integrates on hardware and software level with a commercial multiphoton microscope based on a single 100 fs Ti:Sapphire oscillator and enables D-CARS microscopy in a user-friendly format for applications in the life sciences.

  13. Detecting polymeric nanoparticles with coherent anti-stokes Raman scattering microscopy in tissues exhibiting fixative-induced autofluorescence

    NASA Astrophysics Data System (ADS)

    Garrett, N. L.; Godfrey, L.; Lalatsa, A.; Serrano, D. R.; Uchegbu, I. F.; Schatzlein, A.; Moger, J.

    2015-03-01

    Recent advances in pharmaceutical nanotechnology have enabled the development of nano-particulate medicines with enhanced drug performance. Although the fate of these nano-particles can be macroscopically tracked in the body (e.g. using radio-labeling techniques), there is little information about the sub-cellular scale mechanistic processes underlying the particle-tissue interactions, or how these interactions may correlate with pharmaceutical efficacy. To rationally engineer these nano-particles and thus optimize their performance, these mechanistic interactions must be fully understood. Coherent Anti-Stokes Raman scattering (CARS) microscopy provides a label-free means for visualizing biological samples, but can suffer from a strong non-resonant background in samples that are prepared using aldehyde-based fixatives. We demonstrate how formalin fixative affects the detection of polymeric nanoparticles within kidneys following oral administration using CARS microscopy, compared with samples that were snap-frozen. These findings have implications for clinical applications of CARS for probing nanoparticle distribution in tissue biopsies.

  14. Paranodal myelin retraction in relapsing experimental autoimmune encephalomyelitis visualized by coherent anti-Stokes Raman scattering microscopy

    NASA Astrophysics Data System (ADS)

    Fu, Yan; Frederick, Terra J.; Huff, Terry B.; Goings, Gwendolyn E.; Miller, Stephen D.; Cheng, Ji-Xin

    2011-10-01

    How demyelination is initiated is a standing question for pathology of multiple sclerosis. By label-free coherent anti-Stokes Raman scattering (CARS) imaging of myelin lipids, we investigate myelin integrity in the lumbar spinal cord tissue isolated from naïve SJL mice, and from mice at the onset, peak acute, and remission stages of relapsing experimental autoimmune encephalomyelitis (EAE). Progressive demyelinating disease is initially characterized by the retraction of paranodal myelin both at the onset of disease and at the borders of acute demyelinating lesions. Myelin retraction is confirmed by elongated distribution of neurofascin proteins visualized by immunofluorescence. The disruption of paranodal myelin subsequently exposes Kv1.2 channels at the juxtaparanodes and lead to the displacement of Kv1.2 channels to the paranodal and nodal domains. Paranodal myelin is partially restored during disease remission, indicating spontaneous myelin regeneration. These findings suggest that paranodal domain injury precedes formation of internodal demyelinating lesions in relapsing EAE. Our results also demonstrate that CARS microscopy is an effective readout of myelin disease burden.

  15. Assessment of liver steatosis and fibrosis in rats using integrated coherent anti-Stokes Raman scattering and multiphoton imaging technique

    NASA Astrophysics Data System (ADS)

    Lin, Jian; Lu, Fake; Zheng, Wei; Xu, Shuoyu; Tai, Dean; Yu, Hanry; Huang, Zhiwei

    2011-11-01

    We report the implementation of a unique integrated coherent anti-Stokes Raman scattering (CARS), second-harmonic generation (SHG), and two-photon excitation fluorescence (TPEF) microscopy imaging technique developed for label-free monitoring of the progression of liver steatosis and fibrosis generated in a bile duct ligation (BDL) rat model. Among the 21 adult rats used in this study, 18 rats were performed with BDL surgery and sacrificed each week from weeks 1 to 6 (n = 3 per week), respectively; whereas 3 rats as control were sacrificed at week 0. Colocalized imaging of the aggregated hepatic fats, collagen fibrils, and hepatocyte morphologies in liver tissue is realized by using the integrated CARS, SHG, and TPEF technique. The results show that there are significant accumulations of hepatic lipid droplets and collagen fibrils associated with severe hepatocyte necrosis in BDL rat liver as compared to a normal liver tissue. The volume of normal hepatocytes keeps decreasing and the fiber collagen content in BDL rat liver follows a growing trend until week 6; whereas the hepatic fat content reaches a maximum in week 4 and then appears to stop growing in week 6, indicating that liver steatosis and fibrosis induced in a BDL rat liver model may develop at different rates. This work demonstrates that the integrated CARS and multiphoton microscopy imaging technique has the potential to provide an effective means for early diagnosis and detection of liver steatosis and fibrosis without labeling.

  16. Pressure measurements using hybrid femtosecond/picosecond rotational coherent anti-Stokes Raman scattering.

    PubMed

    Kearney, Sean P; Danehy, Paul M

    2015-09-01

    We investigate the feasibility of gas-phase pressure measurements using fs/ps rotational CARS. Femtosecond pump and Stokes pulses impulsively prepare a rotational Raman coherence, which is probed by a high-energy 5-ps pulse introduced at a time delay from the Raman preparation. These ultrafast laser pulses are shorter than collisional-dephasing time scales, enabling a new hybrid time- and frequency-domain detection scheme for pressure. Single-laser-shot rotational CARS spectra were recorded from N2 contained in a room-temperature gas cell for pressures from 0.4 to 3 atm and probe delays ranging from 16 to 298 ps. Sensitivity of the accuracy and precision of the pressure data to probe delay was investigated. The technique exhibits superior precision and comparable accuracy to previous laser-diagnostic pressure measurements. PMID:26368717

  17. Label-Free Chemical Imaging of Catalytic Solids by Coherent Anti-Stokes Raman Scattering and Synchrotron-Based Infrared Microscopy

    SciTech Connect

    Kox, M.; Domke, K; Day, J; Rago, G; Stavitski, E; Bonn, M; Weckhuysen, B

    2009-01-01

    Take a look inside: The combination of coherent anti-Stokes Raman scattering and synchrotron-based IR microscopy during the catalytic conversion of thiophene derivatives on zeolite crystals yields space- and time-resolved chemically specific information without the need for labeling (see picture). The thiophene reactant is mostly present in the center of the crystal, and the product is aligned within the straight pores of the zeolites.

  18. Exploring the interactions between peptides and lipid bilayers using coherent anti-Stokes Raman scattering and two-photon fluorescence

    NASA Astrophysics Data System (ADS)

    Mari, M.; Mouras, R.; Downes, A.; Elfick, A.

    2011-06-01

    We have used a versatile and powerful microscope[1] for multi-modal biomedical imaging on which we combine Coherent Anti-Stokes Raman Scattering (CARS) with Two Photon Excitation Fluorescence (TPEF) using a Nd: YVO4 pump laser. We acquired 2PEF, CARS, and phase contrast images of Multilamellar Vesicles (MLVs) and Giant Unilamellar Vesicles (GUVs), as well as Raman spectra of the constituent lipids. A wide range of peptides are harmful to cells by altering the structure of the biological membranes. This effect depends on the composition of the membrane and the chemical structure of the peptide. The peptide we studied is the beta amyloid Aβ which is a major component of the amyloid plaques deposited on neuronal membranes of Alzheimer's disease (AD) patients. AD is neurodegenerative disorder in which the hallmark symptoms include cognitive decline and dementia[2] and is characterized by the formation of extracellular amyloid fibrils on the neuronal membranes of the brain. Many questions still remain unanswered concerning the destabilization of cellular ionic homeostasis due to pores formed during the interactions of lipid membranes with peptides. In this project, biomimics of cell membranes are used. The structures that best mimic the plasma membranes are MLVs or GUVs. These vesicles are formed using the gentle hydration technique[3] or the electroformation technique[4] respectively and are composed of phospholipids such as DOPC, DPPC, D62PPC and their binary mixtures. The MLVs and GUVs imaging by CARS and TPEF microscopy not only permits the direct imaging of the leakage phenomenon caused by the toxic peptide (Aβ) on the lipid bilayer, but also records simultaneously the lateral structure of the bilayer and peptide distribution in the plane across the membrane.

  19. In vivo lipid saturation study of C. elegans using quantitative broadband coherent anti-Stokes Raman imaging (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Littleton, Bradley; Kavanagh, Thomas; Nie, Yu; Abbate, Vincenzo; Hylands, Peter; Sturzenbaum, Stephen; Richards, David

    2016-03-01

    In vivo lipid saturation maps of microscopic nematodes (Caenorhabditis elegans) have been produced using our novel Spectral Interferometric Polarisation Coherent anti-Stokes Raman Scattering (SIP-CARS) imaging technique. This technique employs simple passive polarisation optics and a balanced homodyne detection scheme to exploit symmetries in the CARS polarisation response resulting in the complete cancellation of the non-resonant background (NRB) and real component of the CARS signal (with no prior or post assumptions as regards to their form). The remaining imaginary component of the CARS response is linear with analyte concentration and directly relatable to the spontaneous Raman spectrum [1]. Furthermore, the resonant CARS signal is interferometrically amplified by the non-resonant response, a necessity for rapid imaging at biologically relevant powers [2]. This technique permits acquisition of a broad NRB-free spectrum, in excess of 1800cm-1, in a single exposure at each pixel. This allows simultaneous determination of lipid droplet saturation, from the fingerprint region, and lipid order, from the C-H stretch region from which maps can be readily constructed. Additionally exploiting the dispersive nature of our signal collection two-photon autofluorescence can be isolated and images subsequently produced. We have successfully applied this technique to identify differences in lipid saturation distributions in selective C. elegans mutants and demonstrated that the technique is sufficiently sensitive to detect the effects of lipid metabolism altering drugs on wild type C. elegans. [1] Littleton et al, Phys Rev Lett, 111, 103902 (2013) [2] Parekh et al, Biophys J, 99, 2695-2704 (2010)

  20. Temperature measurements in metalized propellant combustion using hybrid fs/ps coherent anti-Stokes Raman scattering

    DOE PAGESBeta

    Kearney, Sean P.; Guildenbecher, Daniel R.

    2016-06-20

    We apply ultrafast pure-rotational coherent anti-Stokes Raman scattering (CARS) for temperature and relative oxygen concentration measurements in the plume emanating from a burning, aluminized ammonium-perchlorate propellant strand. Combustion of these metal-based propellants is a particularly hostile environment for laser-based diagnostics, with intense background luminosity and scattering from hot metal particles as large as several hundred micrometers in diameter. CARS spectra that were previously obtained using nanosecond pulsed lasers in an aluminum-particle-seeded flame are examined and are determined to be severely impacted by nonresonant background, presumably as a result of the plasma formed by particulate-enhanced laser-induced breakdown. Introduction of femtosecond/picosecond (fs/ps)more » laser pulses improves CARS detection by providing time-gated elimination of strong nonresonant background interference. Single-laser-shot fs/ps CARS spectra were acquired from the burning propellant plume, with picosecond probe-pulse delays of 0 and 16 ps from the femtosecond pump and Stokes pulses. At zero delay, nonresonant background overwhelms the Raman-resonant spectroscopic features. Time-delayed probing results in the acquisition of background-free spectra that were successfully fit for temperature and relative oxygen content. Temperature probability densities and temperature/oxygen correlations were constructed from ensembles of several thousand single-laser-shot measurements with the CARS measurement volume positioned within 3 mm or less of the burning propellant surface. Lastly, the results show that ultrafast CARS is a potentially enabling technology for probing harsh, particle-laden flame environments.« less

  1. Temperature measurements in metalized propellant combustion using hybrid fs/ps coherent anti-Stokes Raman scattering.

    PubMed

    Kearney, Sean P; Guildenbecher, Daniel R

    2016-06-20

    We apply ultrafast pure-rotational coherent anti-Stokes Raman scattering (CARS) for temperature and relative oxygen concentration measurements in the plume emanating from a burning, aluminized ammonium-perchlorate propellant strand. Combustion of these metal-based propellants is a particularly hostile environment for laser-based diagnostics, with intense background luminosity and scattering from hot metal particles as large as several hundred micrometers in diameter. CARS spectra that were previously obtained using nanosecond pulsed lasers in an aluminum-particle-seeded flame are examined and are determined to be severely impacted by nonresonant background, presumably as a result of the plasma formed by particulate-enhanced laser-induced breakdown. Introduction of femtosecond/picosecond (fs/ps) laser pulses improves CARS detection by providing time-gated elimination of strong nonresonant background interference. Single-laser-shot fs/ps CARS spectra were acquired from the burning propellant plume, with picosecond probe-pulse delays of 0 and 16 ps from the femtosecond pump and Stokes pulses. At zero delay, nonresonant background overwhelms the Raman-resonant spectroscopic features. Time-delayed probing results in the acquisition of background-free spectra that were successfully fit for temperature and relative oxygen content. Temperature probability densities and temperature/oxygen correlations were constructed from ensembles of several thousand single-laser-shot measurements with the CARS measurement volume positioned within 3 mm or less of the burning propellant surface. The results show that ultrafast CARS is a potentially enabling technology for probing harsh, particle-laden flame environments. PMID:27409125

  2. Raman spectroscopies in shock-compressed materials

    SciTech Connect

    Schmidt, S.C.; Moore, D.S.; Shaner, J.W.

    1983-01-01

    Spontaneous Raman spectroscopy, stimulated Raman scattering and coherent anti-Stokes Raman scattering have been used to measure temperatures and changes in molecular vibrational frequencies for detonating and shocked materials. Inverse Raman and Raman induced Kerr effect spectroscopies have been suggested as diagnostic probes for determining and phenomenology of shock-induced chemical reactions. The practicality, advantages, and disadvantages of using Raman scattering techniques as diagnostic probes of microscopic phenomenology through and immediately behind the shock front of shock-compressed molecular systems are discussed.

  3. Ultrafast saturation of electronic-resonance-enhanced coherent anti-Stokes Raman scattering and comparison for pulse durations in the nanosecond to femtosecond regime

    NASA Astrophysics Data System (ADS)

    Patnaik, Anil K.; Roy, Sukesh; Gord, James R.

    2016-02-01

    The saturation threshold of a probe pulse in an ultrafast electronic-resonance-enhanced (ERE) coherent anti-Stokes Raman spectroscopy (CARS) configuration is calculated. We demonstrate that while the underdamping condition is a sufficient condition for saturation of ERE-CARS with the long-pulse excitations, a transient gain must be achieved to saturate the ERE-CARS signal for the ultrafast probe regime. We identify that the area under the probe pulse can be used as a definitive parameter to determine the criterion for a saturation threshold for ultrafast ERE-CARS. From a simplified analytical solution and a detailed numerical calculation based on density-matrix equations, the saturation threshold of ERE-CARS is compared for a wide range of probe-pulse durations from the 10-ns to the 10-fs regime. The theory explains both qualitatively and quantitatively the saturation thresholds of resonant transitions and also gives a predictive capability for other pulse duration regimes. The presented criterion for the saturation threshold will be useful in establishing the design parameters for ultrafast ERE-CARS.

  4. Imaging the Effects of Prostaglandin Analogues on Cultured Trabecular Meshwork Cells by Coherent Anti-Stokes Raman Scattering

    PubMed Central

    Lei, Tim C.; Masihzadeh, Omid; Kahook, Malik Y.; Ammar, David A.

    2013-01-01

    Purpose. The aim of this study was to nondestructively monitor morphological changes to the lipid membranes of primary cultures of living human trabecular meshwork cells (hTMC) without the application of exogenous label. Methods. Live hTMC were imaged using two nonlinear optical techniques: coherent anti-Stokes Raman scattering (CARS) and two-photon autofluorescence (TPAF). The hTMC were treated with a commercial formulation of latanoprost (0.5 μg/mL) for 24 hours before imaging. Untreated cells and cells treated with vehicle containing the preservative benzalkonium chloride (BAK; 2 μg/mL) were imaged as controls. After CARS/TPAF imaging, hTMC were fixed, stained with the fluorescent lipid dye Nile Red, and imaged by conventional confocal microscopy to verify lipid membrane structures. Results. Analysis of CARS/TPAF images of hTMC treated with latanoprost revealed multiple intracellular lipid membranes absent from untreated or BAK-treated hTMC. Treatment of hTMC with sodium fluoride or ouabain, agents shown to cause morphological changes to hTMC, also did not induce formation of intracellular lipid membranes. Conclusions. CARS microscopy detected changes in living hTMC morphology that were validated by subsequent histological stain. Prostaglandin-induced changes to hTMC involved rearrangement of lipid membranes within these cells. These in vitro results identify a novel biological response to a class of antiglaucoma drugs, and further experiments are needed to establish how this effect is involved in the hypotensive action of prostaglandin analogues in vivo. PMID:23900606

  5. Expanding multimodal microscopy by high spectral resolution coherent anti-Stokes Raman scattering imaging for clinical disease diagnostics.

    PubMed

    Meyer, Tobias; Chemnitz, Mario; Baumgartl, Martin; Gottschall, Thomas; Pascher, Torbjörn; Matthäus, Christian; Romeike, Bernd F M; Brehm, Bernhard R; Limpert, Jens; Tünnermann, Andreas; Schmitt, Michael; Dietzek, Benjamin; Popp, Jürgen

    2013-07-16

    Over the past years fast label-free nonlinear imaging modalities providing molecular contrast of endogenous disease markers with subcellular spatial resolution have been emerged. However, applications of these imaging modalities in clinical settings are still at the very beginning. This is because single nonlinear imaging modalities such as second-harmonic generation (SHG) and two-photon excited fluorescence (TPEF) have only limited value for diagnosing diseases due to the small number of endogenous markers. Coherent anti-Stokes Raman scattering (CARS) microscopy on the other hand can potentially be added to SHG and TPEF to visualize a much broader range of marker molecules. However, CARS requires a second synchronized laser source and the detection of a certain wavenumber range of the vibrational spectrum to differentiate multiple molecules, which results in increased experimental complexity and often inefficient excitation of SHG and TPEF signals. Here we report the application of a novel near-infrared (NIR) fiber laser of 1 MHz repetition rate, 65 ps pulse duration, and 1 cm(-1) spectral resolution to realize an efficient but experimentally simple SGH/TPEF/multiplex CARS multimodal imaging approach for a label-free characterization of composition of complex tissue samples. This is demonstrated for arterial tissue specimens demonstrating differentiation of elastic fibers, triglycerides, collagen, myelin, cellular cytoplasm, and lipid droplets by analyzing the CARS spectra within the C-H stretching region only. A novel image analysis approach for multispectral CARS data based on colocalization allows correlating spectrally distinct pixels to morphologic structures. Transfer of this highly precise but compact and simple to use imaging approach into clinical settings is expected in the near future. PMID:23781826

  6. Dynamical study of the water penetration process into a cellulose acetate film studied by coherent anti-Stokes Raman scattering (CARS) microspectroscopy

    NASA Astrophysics Data System (ADS)

    Fujisawa, Rie; Ohno, Tomoya; Kaneyasu, Junya F.; Leproux, Philippe; Couderc, Vincent; Kita, Hiroshi; Kano, Hideaki

    2016-07-01

    The penetration process of water into a cellulose acetate film was traced in real time by coherent anti-Stokes Raman scattering (CARS) microspectroscopy. The Cdbnd O stretch mode was red-shifted due to hydrogen-bond formation. We also found that two Raman bands at 1605 cm-1 and 1665 cm-1 emerged only in the early stage of the water penetration process. Based on the combined analysis of the experimental and computational studies, these bands at 1605 cm-1 and 1665 cm-1 were assigned as the OH bend mode due to hydrogen-bonded penetrated water and hydrogen-bonded OH groups in pyranose rings, respectively.

  7. Coherent anti-Stokes Raman scattering in isolated air-guided modes of a hollow-core photonic-crystal fiber

    SciTech Connect

    Fedotov, A.B.; Zheltikov, A.M.; Konorov, S.O.; Mitrokhin, V.P.; Serebryannikov, E.E

    2004-10-01

    Hollow-core photonic-crystal fibers are shown to offer the unique possibility of coherent excitation and probing of Raman-active vibrations in molecules by isolated air-guided modes of electromagnetic radiation. A 3-cm section of a hollow photonic-crystal fiber is used to prepare isolated air-guided modes of pump and probe fields for a coherent excitation of 2331-cm{sup -1} Q-branch vibrations of molecular nitrogen in the gas filling the fiber core, enhancing coherent anti-Stokes Raman scattering through these vibrations by a factor of 15 relative to the regime of tight focusing.

  8. Raman Spectroscopy and Related Techniques in Biomedicine

    PubMed Central

    Downes, Andrew; Elfick, Alistair

    2010-01-01

    In this review we describe label-free optical spectroscopy techniques which are able to non-invasively measure the (bio)chemistry in biological systems. Raman spectroscopy uses visible or near-infrared light to measure a spectrum of vibrational bonds in seconds. Coherent anti-Stokes Raman (CARS) microscopy and stimulated Raman loss (SRL) microscopy are orders of magnitude more efficient than Raman spectroscopy, and are able to acquire high quality chemically-specific images in seconds. We discuss the benefits and limitations of all techniques, with particular emphasis on applications in biomedicine—both in vivo (using fiber endoscopes) and in vitro (in optical microscopes). PMID:21151763

  9. Estimated phase transition and melting temperature of APTES self-assembled monolayer using surface-enhanced anti-stokes and stokes Raman scattering

    NASA Astrophysics Data System (ADS)

    Sun, Yingying; Yanagisawa, Masahiro; Kunimoto, Masahiro; Nakamura, Masatoshi; Homma, Takayuki

    2016-02-01

    A structure's temperature can be determined from the Raman spectrum using the frequency and the ratio of the intensities of the anti-Stokes and Stokes signals (the Ias/Is ratio). In this study, we apply this approach and an equation relating the temperature, Raman frequency, and Ias/Is ratio to in-situ estimation of the phase change point of a (3-aminopropyl)triethoxysilane self-assembled monolayer (APTES SAM). Ag nanoparticles were deposited on APTES to enhance the Raman signals. A time-resolved measurement mode was used to monitor the variation in the Raman spectra in situ. Moreover, the structural change in APTES SAM (from ordered to disordered structure) under heating was discussed in detail, and the phase change point (around 118 °C) was calculated.

  10. A triple-resonance Raman chip for simultaneous enhancement of Stokes and anti-Stokes lines utilizing both localized and non-localized plasmonic resonance

    NASA Astrophysics Data System (ADS)

    Lin, Jiao; Zhang, Yuan; Lee, El-Hang; He, Sailing

    2015-10-01

    In this paper we report a triple-resonance surface-enhanced Raman scattering (SERS) chip that is able to provide simultaneous field enhancement for both the Stokes and anti-Stokes lines. The structure consists of an array of periodic gold bowties placed on the surface of a uniform gold film. It can support two localized surface plasmonic resonances (LSPRs): an electric dipole binding resonance (EDBR) and a magnetic dipole resonance (MDR). A third field enhancement peak is obtained by utilizing the strong interaction between the non-localized surface plasmonic resonance (non-localized SPR) and the LSPR, which greatly raises the field enhancement for the non-localized SPR. In addition, a gold strip-line resonator is incorporated to further enhance the local field intensity. Consequently, the field enhancement of the three peaks are all increased. Compared with the same structure without strip, the periodic bowtie-strip compound structure on gold film can gain as much as ∼22.8 times and ∼3.6 times larger Raman intensity enhancement simultaneously for both the Stokes and anti-Stokes lines.

  11. Raman Spectroscopy.

    ERIC Educational Resources Information Center

    Gerrard, Donald L.

    1984-01-01

    Reviews literature on Raman spectroscopy from late 1981 to late 1983. Topic areas include: instrumentation and sampling; liquids and solutions; gases and matrix isolation; biological molecules; polymers; high-temperature and high-pressure studies; Raman microscopy; thin films and surfaces; resonance-enhanced and surface-enhanced spectroscopy; and…

  12. Interference-free gas-phase thermometry at elevated pressure using hybrid femtosecond/picosecond rotational coherent anti-Stokes Raman scattering.

    PubMed

    Miller, Joseph D; Dedic, Chloe E; Roy, Sukesh; Gord, James R; Meyer, Terrence R

    2012-02-27

    Rotational-level-dependent dephasing rates and nonresonant background can lead to significant uncertainties in coherent anti-Stokes Raman scattering (CARS) thermometry under high-pressure, low-temperature conditions if the gas composition is unknown. Hybrid femtosecond/picosecond rotational CARS is employed to minimize or eliminate the influence of collisions and nonresonant background for accurate, frequency-domain thermometry at elevated pressure. The ability to ignore these interferences and achieve thermometric errors of <5% is demonstrated for N2 and O2 at pressures up to 15 atm. Beyond 15 atm, the effects of collisions cannot be ignored but can be minimized using a short probe delay (~6.5 ps) after Raman excitation, thereby improving thermometric accuracy with a time- and frequency-resolved theoretical model. PMID:22418304

  13. Quantitative, Label-Free Characterization of Stem Cell Differentiation at the Single-Cell Level by Broadband Coherent Anti-Stokes Raman Scattering Microscopy

    PubMed Central

    Lee, Young Jong; Vega, Sebastián L.; Patel, Parth J.; Aamer, Khaled A.; Moghe, Prabhas V.

    2014-01-01

    We use broadband coherent anti-Stokes Raman scattering (BCARS) microscopy to characterize lineage commitment of individual human mesenchymal stem cells cultured in adipogenic, osteogenic, and basal culture media. We treat hyperspectral images obtained by BCARS in two independent ways, obtaining robust metrics for differentiation. In one approach, pixel counts corresponding to functional markers, lipids, and minerals, are used to classify individual cells as belonging to one of the three lineage groups: adipocytes, osteoblasts, and undifferentiated stem cells. In the second approach, we use multivariate analysis of Raman spectra averaged exclusively over cytosol regions of individual cells to classify the cells into the same three groups, with consistent results. The exceptionally high speed of spectral imaging with BCARS allows us to chemically map a large number of cells with high spatial resolution, revealing not only the phenotype of individual cells, but also population heterogeneity in the degree of phenotype commitment. PMID:24224876

  14. Emerging technology: applications of Raman spectroscopy for prostate cancer.

    PubMed

    Kast, Rachel E; Tucker, Stephanie C; Killian, Kevin; Trexler, Micaela; Honn, Kenneth V; Auner, Gregory W

    2014-09-01

    There is a need in prostate cancer diagnostics and research for a label-free imaging methodology that is nondestructive, rapid, objective, and uninfluenced by water. Raman spectroscopy provides a molecular signature, which can be scaled from micron-level regions of interest in cells to macroscopic areas of tissue. It can be used for applications ranging from in vivo or in vitro diagnostics to basic science laboratory testing. This work describes the fundamentals of Raman spectroscopy and complementary techniques including surface enhanced Raman scattering, resonance Raman spectroscopy, coherent anti-Stokes Raman spectroscopy, confocal Raman spectroscopy, stimulated Raman scattering, and spatially offset Raman spectroscopy. Clinical applications of Raman spectroscopy to prostate cancer will be discussed, including screening, biopsy, margin assessment, and monitoring of treatment efficacy. Laboratory applications including cell identification, culture monitoring, therapeutics development, and live imaging of cellular processes are discussed. Potential future avenues of research are described, with emphasis on multiplexing Raman spectroscopy with other modalities. PMID:24510129

  15. In planta imaging of Δ9-tetrahydrocannabinolic acid in Cannabis sativa L. with hyperspectral coherent anti-Stokes Raman scattering microscopy

    NASA Astrophysics Data System (ADS)

    Garbacik, Erik T.; Korai, Roza P.; Frater, Eric H.; Korterik, Jeroen P.; Otto, Cees; Offerhaus, Herman L.

    2013-04-01

    Nature has developed many pathways to produce medicinal products of extraordinary potency and specificity with significantly higher efficiencies than current synthetic methods can achieve. Identification of these mechanisms and their precise locations within plants could substantially increase the yield of a number of natural pharmaceutics. We report label-free imaging of Δ9-tetrahydrocannabinolic acid (THCa) in Cannabis sativa L. using coherent anti-Stokes Raman scattering microscopy. In line with previous observations we find high concentrations of THCa in pistillate flowering bodies and relatively low amounts within flowering bracts. Surprisingly, we find differences in the local morphologies of the THCa-containing bodies: organelles within bracts are large, diffuse, and spheroidal, whereas in pistillate flowers they are generally compact, dense, and have heterogeneous structures. We have also identified two distinct vibrational signatures associated with THCa, both in pure crystalline form and within Cannabis plants; at present the exact natures of these spectra remain an open question.

  16. Hyperspectral imaging and characterization of live cells by broadband coherent anti-Stokes Raman scattering (CARS) microscopy with singular value decomposition (SVD) analysis.

    PubMed

    Khmaladze, Alexander; Jasensky, Joshua; Price, Erika; Zhang, Chi; Boughton, Andrew; Han, Xiaofeng; Seeley, Emily; Liu, Xinran; Banaszak Holl, Mark M; Chen, Zhan

    2014-01-01

    Coherent anti-Stokes Raman scattering (CARS) microscopy can be used as a powerful imaging technique to identify chemical compositions of complex samples in biology, biophysics, medicine, and materials science. In this work we developed a CARS microscopic system capable of hyperspectral imaging. By employing an ultrafast laser source, a photonic crystal fiber, and a scanning laser microscope together with spectral detection by a highly sensitive back-illuminated cooled charge-coupled device (CCD) camera, we were able to rapidly acquire and process hyperspectral images of live cells with chemical selectivity. We discuss various aspects of hyperspectral CARS image analysis and demonstrate the use of singular value decomposition methods to characterize the cellular lipid content. PMID:25198903

  17. Hybrid femtosecond/picosecond rotational coherent anti-Stokes Raman scattering at flame temperatures using a second-harmonic bandwidth-compressed probe.

    PubMed

    Kearney, Sean P; Scoglietti, Daniel J

    2013-03-15

    We demonstrate an approach for picosecond probe-beam generation that enables hybrid femtosecond/picosecond pure-rotational coherent anti-Stokes Raman scattering (CARS) measurements in flames. Sum-frequency generation of bandwidth-compressed picosecond radiation from femtosecond pumps with phase-conjugate chirps provides probe pulses with energies in excess of 1 mJ that are temporally locked to the femtosecond pump/Stokes preparation. This method overcomes previous limitations on hybrid femtosecond/picosecond rotational CARS techniques, which have relied upon less efficient bandwidth-reduction processes that have generally resulted in prohibitively low probe energy for flame measurements. We provide the details of the second-harmonic approach and demonstrate the technique in near-adiabatic hydrogen/air flames. PMID:23503231

  18. Raman spectroscopy

    SciTech Connect

    Gerrard, D.L.; Bowley, H.J.

    1986-04-01

    The period of this review is from late 1983 to late 1985. During this time over 5000 papers have appeared in the scientific literature dealing with many applications of Raman spectroscopy and extending its use to several new areas of study. As in the previous review in this series most of the applications relevant to solids are covered in one or other of the ten categories, which are the same as those used previously. However, aspects relating to solids which are not covered elsewhere include general reviews and the specific field of semiconductors. This is an area of great current interest in terms of Raman spectroscopy and the characterization of semiconductor materials and surfaces has been reported. Raman scattering also provides a new probe for the elucidation of structural properties of microcrystalline silicon and resonance Raman scattering in silicon at elevated temperatures has been studied. Many studies on carbon have also appeared in the literature including that of the various types of carbon, the use of Raman scattering to investigate disorder and crystallite formation in annealed carbon, in situ studies of intercalation kinetics, structural aspects of cokes and coals, and instrumentation for coal gasification. Raman spectroscopy has been applied to such diverse systems as organic crystals, the determination of modifications in layered crystals, the detection of explosives on silica gel or carbon, diagnostics of heterogeneous chemical processes, and a study of tungsten-halogen bulbs. Laser Raman spectroscopy has also been coupled with liquid chromatography and phase-resolved background suppression has been used to enhance Raman spectra. 397 references.

  19. New topics in coherent anti-stokes raman scattering gas-phase diagnostics : femtosecond rotational CARS and electric-field measurements.

    SciTech Connect

    Lempert, Walter R.; Barnat, Edward V.; Kearney, Sean Patrick; Serrano, Justin Raymond

    2010-07-01

    We discuss two recent diagnostic-development efforts in our laboratory: femtosecond pure-rotational Coherent anti-Stokes Raman scattering (CARS) for thermometry and species detection in nitrogen and air, and nanosecond vibrational CARS measurements of electric fields in air. Transient pure-rotational fs-CARS data show the evolution of the rotational Raman polarization in nitrogen and air over the first 20 ps after impulsive pump/Stokes excitation. The Raman-resonant signal strength at long time delays is large, and we additionally observe large time separation between the fs-CARS signatures of nitrogen and oxygen, so that the pure-rotational approach to fs-CARS has promise for simultaneous species and temperature measurements with suppressed nonresonant background. Nanosecond vibrational CARS of nitrogen for electric-field measurements is also demonstrated. In the presence of an electric field, a dipole is induced in the otherwise nonpolar nitrogen molecule, which can be probed with the introduction of strong collinear pump and Stokes fields, resulting in CARS signal radiation in the infrared. The electric-field diagnostic is demonstrated in air, where the strength of the coherent infrared emission and sensitivity our field measurements is quantified, and the scaling of the infrared signal with field strength is verified.

  20. Implementation of a Coherent Anti-Stokes Raman Scattering (CARS) System on a Ti:Sapphire and OPO Laser Based Standard Laser Scanning Microscope.

    PubMed

    Mytskaniuk, Vasyl; Bardin, Fabrice; Boukhaddaoui, Hassan; Rigneault, Herve; Tricaud, Nicolas

    2016-01-01

    Laser scanning microscopes combining a femtosecond Ti:sapphire laser and an optical parametric oscillator (OPO) to duplicate the laser line have become available for biologists. These systems are primarily designed for multi-channel two-photon fluorescence microscopy. However, without any modification, complementary non-linear optical microscopy such as second-harmonic generation (SHG) or third harmonic generation (THG) can also be performed with this set-up, allowing label-free imaging of structured molecules or aqueous medium-lipid interfaces. These techniques are well suited for in-vivo observation, but are limited in chemical specificity. Chemically selective imaging can be obtained from inherent vibration signals based on Raman scattering. Confocal Raman microscopy provides 3D spatial resolution, but it requires high average power and long acquisition time. To overcome these difficulties, recent advances in laser technology have permitted the development of nonlinear optical vibrational microscopy, in particular coherent anti-Stokes Raman scattering (CARS). CARS microscopy has therefore emerged as a powerful tool for biological and live cell imaging, by chemically mapping lipids (via C-H stretch vibration), water (via O-H stretch vibrations), proteins or DNA. In this work, we describe the implementation of the CARS technique on a standard OPO-coupled multiphoton laser scanning microscope. It is based on the in-time synchronization of the two laser lines by adjusting the length of one of the laser beam path. We present a step-by-step implementation of this technique on an existing multiphoton system. A basic background in experimental optics is helpful and the presented system does not require expensive supplementary equipment. We also illustrate CARS imaging obtained on myelin sheaths of sciatic nerve of rodent, and we show that this imaging can be performed simultaneously with other nonlinear optical imaging, such as standard two-photon fluorescence technique

  1. Single-shot gas-phase thermometry using pure-rotational hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering.

    PubMed

    Miller, Joseph D; Roy, Sukesh; Slipchenko, Mikhail N; Gord, James R; Meyer, Terrence R

    2011-08-01

    High-repetition-rate, single-laser-shot measurements are important for the investigation of unsteady flows where temperature and species concentrations can vary significantly. Here, we demonstrate single-shot, pure-rotational, hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps RCARS) thermometry based on a kHz-rate fs laser source. Interferences that can affect nanosecond (ns) and ps CARS, such as nonresonant background and collisional dephasing, are eliminated by selecting an appropriate time delay between the 100-fs pump/Stokes pulses and the pulse-shaped 8.4-ps probe. A time- and frequency-domain theoretical model is introduced to account for rotational-level dependent collisional dephasing and indicates that the optimal probe-pulse time delay is 13.5 ps to 30 ps. This time delay allows for uncorrected best-fit N2-RCARS temperature measurements with ~1% accuracy. Hence, the hybrid fs/ps RCARS approach can be performed with kHz-rate laser sources while avoiding corrections that can be difficult to predict in unsteady flows. PMID:21934925

  2. Label-free imaging of Drosophila in vivo by coherent anti-Stokes Raman scattering and two-photon excitation autofluorescence microscopy

    NASA Astrophysics Data System (ADS)

    Chien, Cheng-Hao; Chen, Wei-Wen; Wu, June-Tai; Chang, Ta-Chau

    2011-01-01

    Drosophila is one of the most valuable model organisms for studying genetics and developmental biology. The fat body in Drosophila, which is analogous to the liver and adipose tissue in human, stores lipids that act as an energy source during its development. At the early stages of metamorphosis, the fat body remodeling occurs involving the dissociation of the fat body into individual fat cells. Here we introduce a combination of coherent anti-Stokes Raman scattering (CARS) and two-photon excitation autofluorescence (TPE-F) microscopy to achieve label-free imaging of Drosophila in vivo at larval and pupal stages. The strong CARS signal from lipids allows direct imaging of the larval fat body and pupal fat cells. In addition, the use of TPE-F microscopy allows the observation of other internal organs in the larva and autofluorescent globules in fat cells. During the dissociation of the fat body, the findings of the degradation of lipid droplets and an increase in autofluorescent globules indicate the consumption of lipids and the recruitment of proteins in fat cells. Through in vivo imaging and direct monitoring, CARS microscopy may help elucidate how metamorphosis is regulated and study the lipid metabolism in Drosophila.

  3. Measurement of vibrationally excited N2(v) in an atmospheric-pressure air pulsed corona discharge using coherent anti-Stokes Raman scattering

    NASA Astrophysics Data System (ADS)

    Teramoto, Yoshiyuki; Ono, Ryo

    2014-08-01

    Vibrationally excited N2(v = 1, 2) in an atmospheric-pressure air pulsed corona discharge was measured using coherent anti-Stokes Raman scattering (CARS). In a dry air discharge, the vibrational temperature determined from the ratio N2(v = 2)/N2(v = 0), Tv2, was approximately 500 K higher than that determined from N2(v = 1)/N2(v = 0), Tv1, immediately after the discharge pulse. Both vibrational temperatures reached equilibrium within 100 μs after the discharge pulse by the vibration-to-vibration (V-V) process of N2-N2. The translational temperature was also measured using CARS. The rise in the translational temperature due to vibration-to-translation (V-T) energy transfer was not observed for a postdischarge time of 5 μs-1 ms in the dry-air discharge. However, when the air was humidified, a significant V-T energy transfer was observed. It was due to an extremely rapid V-T process of H2O-H2O following the V-V process of N2-H2O. Measurements showed that the humidification of the ambient air accelerated the decrease in the N2 vibrational temperature and increased the translational temperature. N2(v) was generated mostly in the secondary streamer, not in the primary one, according to estimation from the measured N2(v) density.

  4. Lipid droplet pattern and nondroplet-like structure in two fat mutants of Caenorhabditis elegans revealed by coherent anti-Stokes Raman scattering microscopy.

    PubMed

    Yi, Yung-Hsiang; Chien, Cheng-Hao; Chen, Wei-Wen; Ma, Tian-Hsiang; Liu, Kuan-Yu; Chang, Yu-Sun; Chang, Ta-Chau; Lo, Szecheng J

    2014-01-01

    Lipid is an important energy source and essential component for plasma and organelle membranes in all kinds of cells. Coherent anti-Stokes Raman scattering (CARS) microscopy is a label-free and nonlinear optical technique that can be used to monitor the lipid distribution in live organisms. Here, we utilize CARS microscopy to investigate the pattern of lipid droplets in two live Caenorhabditis elegans mutants (fat-2 and fat-3). The CARS images showed a striking decrease in the size, number, and content of lipid droplets in the fat-2 mutant but a slight difference in the fat-3 mutant as compared with the wild-type worm. Moreover, a nondroplet-like structure with enhanced CARS signal was detected for the first time in the uterus of fat-2 and fat-3 mutants. In addition, transgenic fat-2 mutant expressing a GFP fusion protein of vitellogenin-2 (a yolk lipoprotein) revealed that the enhanced CARS signal colocalized with the GFP signal, which suggests that the nondroplet-like structure is primarily due to the accumulation of yolk lipoproteins. Together, this study implies that CARS microscopy is a potential tool to study the distribution of yolk lipoproteins, in addition to lipid droplets, in live animals. PMID:23979461

  5. Time-resolved CO2 thermometry for pressures as great as 5 MPa by use of pure rotational coherent anti-Stokes Raman scattering

    SciTech Connect

    Schenk, Martin; Seeger, Thomas; Leipertz, Alfred

    2005-11-01

    Pure rotational coherent anti-Stokes Raman scattering measurements of pure CO2 have been performed in a temperature range from 300 to 773 K and for pressure from 0.1 to 5 MPa for the purpose of time-resolved CO2 thermometry. Particular emphasis was put on the comparison of several linewidth approximations to model the experimental spectra. Generally good agreement of the temperature mean values with the thermocouple reference has been found for all models over almost the whole pressure and temperature range investigated. The standard deviations, which increased with temperature, were comparable with or better than the results gained for single-shot measurements of pure N2 or O2-N2 mixtures. Yet for high particle densities close to the critical point of CO2 the limitation of the models became obvious, owing to the strongly increased influence of motional narrowing effects. The characteristics of these effects have been demonstrated by measurements even closer to the critical conditions.

  6. Multimodal coherent anti-Stokes Raman scattering microscopy reveals microglia-associated myelin and axonal dysfunction in multiple sclerosis-like lesions in mice

    NASA Astrophysics Data System (ADS)

    Imitola, Jaime; Côté, Daniel; Rasmussen, Stine; Xie, X. Sunney; Liu, Yingru; Chitnis, Tanuja; Sidman, Richard L.; Lin, Charles. P.; Khoury, Samia J.

    2011-02-01

    Myelin loss and axonal degeneration predominate in many neurological disorders; however, methods to visualize them simultaneously in live tissue are unavailable. We describe a new imaging strategy combining video rate reflectance and fluorescence confocal imaging with coherent anti-Stokes Raman scattering (CARS) microscopy tuned to CH2 vibration of myelin lipids, applied in live tissue of animals with chronic experimental autoimmune encephalomyelitis (EAE). Our method allows monitoring over time of demyelination and neurodegeneration in brain slices with high spatial resolution and signal-to-noise ratio. Local areas of severe loss of lipid signal indicative of demyelination and loss of the reflectance signal from axons were seen in the corpus callosum and spinal cord of EAE animals. Even in myelinated areas of EAE mice, the intensity of myelin lipid signals is significantly reduced. Using heterozygous knock-in mice in which green fluorescent protein replaces the CX3CR1 coding sequence that labels central nervous system microglia, we find areas of activated microglia colocalized with areas of altered reflectance and CARS signals reflecting axonal injury and demyelination. Our data demonstrate the use of multimodal CARS microscopy for characterization of demyelinating and neurodegenerative pathology in a mouse model of multiple sclerosis, and further confirm the critical role of microglia in chronic inflammatory neurodegeneration.

  7. Impact of refractive index mismatches on coherent anti-Stokes Raman scattering and multiphoton autofluorescence tomography of human skin in vivo.

    PubMed

    Weinigel, M; Breunig, H G; Darvin, M E; Klemp, M; Röwert-Huber, J; Lademann, J; König, K

    2015-09-01

    Optical non-linear multimodal tomography is a powerful diagnostic imaging tool to analyse human skin based on its autofluorescence and second-harmonic generation signals. Recently, the field of clinical non-linear imaging has been extended by adding coherent anti-Stokes Raman scattering (CARS)-a further optical sectioning method for the detection of non-fluorescent molecules. However, the heterogeneity of refractive indices of different substances in complex tissues like human skin can have a strong influence on CARS image formation and requires careful clinical interpretation of the detected signals. Interestingly, very regular patterns are present in the CARS images, which have no correspondence to the morphology revealed by autofluorescence at the same depth. The purpose of this paper is to clarify this phenomenon and to sensitize users for possible artefacts. A further part of this paper is the detailed comparison of CARS and autofluorescence images of healthy human skin in vivo covering the complete epidermis and part of the upper dermis by employing the flexible medical non-linear tomograph MPTflex CARS. PMID:26305454

  8. Single-shot gas-phase thermometry using pure-rotational hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering

    NASA Astrophysics Data System (ADS)

    Miller, Joseph D.; Roy, Sukesh; Slipchenko, Mikhail N.; Gord, James R.; Meyer, Terrence R.

    2011-08-01

    High-repetition-rate, single-laser-shot measurements are important for the investigation of unsteady flows where temperature and species concentrations can vary significantly. Here, we demonstrate single-shot, pure-rotational, hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps RCARS) thermometry based on a kHz-rate fs laser source. Interferences that can affect nanosecond (ns) and ps CARS, such as nonresonant background and collisional dephasing, are eliminated by selecting an appropriate time delay between the 100-fs pump/Stokes pulses and the pulse-shaped 8.4-ps probe. A time- and frequency-domain theoretical model is introduced to account for rotational-level dependent collisional dephasing and indicates that the optimal probe-pulse time delay is 13.5 ps to 30 ps. This time delay allows for uncorrected best-fit N2-RCARS temperature measurements with ~1% accuracy. Hence, the hybrid fs/ps RCARS approach can be performed with kHz-rate laser sources while avoiding corrections that can be difficult to predict in unsteady flows.

  9. Coherent anti-Stokes Raman scattering microscope with a high-signal-to-noise ratio, high stability, and high-speed imaging for live cell observation

    NASA Astrophysics Data System (ADS)

    Hayashi, Shinichi; Takimoto, Shinichi; Hashimoto, Takeshi

    2007-02-01

    Coherent anti-Stokes Raman scattering (CARS) microscopy, which can produce images of specific molecules without staining, has attracted the attention of researchers, as it matches the need for molecular imaging and pathway analysis of live cells. In particular, there have been an increasing number of CARS experimental results regarding lipids in live cells, which cannot be fluorescently tagged while keeping the cells alive. One of the important applications of lipid research is for the metabolic syndrome. Since the metabolic syndrome is said to be related to the lipids in lipocytes, blood, arterial vessels, and so on, the CARS technique is expected to find application in this field. However, CARS microscopy requires a pair of picosecond laser pulses, which overlap both temporally and spatially. This makes the optical adjustments of a CARS microscope challenging. The authors developed a CARS unit that includes optics for easy and stable adjustment of the overlap of these laser pulses. Adding the CARS unit to a laser scanning microscope provides CARS images of a high signal-to-noise ratio, with an acquisition rate as high as 2 microseconds per pixel. Thus, images of fast-moving lipid droplets in Hela cells were obtained.

  10. Investigation of protein distribution in solid lipid particles and its impact on protein release using coherent anti-Stokes Raman scattering microscopy.

    PubMed

    Christophersen, Philip C; Birch, Ditlev; Saarinen, Jukka; Isomäki, Antti; Nielsen, Hanne M; Yang, Mingshi; Strachan, Clare J; Mu, Huiling

    2015-01-10

    The aim of this study was to gain new insights into protein distribution in solid lipid microparticles (SLMs) and subsequent release mechanisms using a novel label-free chemical imaging method, coherent anti-Stokes Raman scattering (CARS) microscopy. Lysozyme-loaded SLMs were prepared using different lipids with lysozyme incorporated either as an aqueous solution or as a solid powder. Lysozyme distribution in SLMs was investigated using CARS microscopy with supportive structural analysis using electron microscopy. The release of lysozyme from SLMs was investigated in a medium simulating the conditions in the human duodenum. Both preparation method and lipid excipient affected the lysozyme distribution and release from SLMs. Lysozyme resided in a hollow core within the SLMs when incorporated as an aqueous solution. In contrast, lysozyme incorporated as a solid was embedded in clusters in the solid lipid matrix, which required full lipolysis of the entire matrix to release lysozyme completely. Therefore, SLMs with lysozyme incorporated in an aqueous solution released lysozyme much faster than with lysozyme incorporated as a solid. In conclusion, CARS microscopy was an efficient and non-destructive method for elucidating the distribution of lysozyme in SLMs. The interpretation of protein distribution and release during lipolysis enabled elucidation of protein release mechanisms. In future, CARS microscopy analysis could facilitate development of a wide range of protein-lipid matrices with tailor-made controlled release properties. PMID:25449810