Coherent anti-Stokes Raman scattering spectral interferometry: determination of the real and imaginary components of nonlinear susceptibility chi((3)) for vibrational microscopy

Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, USA.
Optics Letters (Impact Factor: 3.18). 01/2005; 29(24):2923-5. DOI: 10.1364/OL.29.002923
Source: PubMed

ABSTRACT We demonstrate coherent anti-Stokes Raman scattering (CARS) heterodyne spectral interferometry for retrieval of the real and imaginary components of the third-order nonlinear susceptibility (chi(3)) of molecular vibrations. Extraction of the imaginary component of chi(3) allows a straightforward reconstruction of the vibrationally resonant signal that is completely free of the electronic nonresonant background and resembles the spontaneous Raman spectrum. Heterodyne detection offers potential for signal amplification and enhanced sensitivity for CARS microscopy.

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Available from: Conor Evans, Mar 21, 2014
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    • "This non-resonant background exists even in pure substances because multiple pathways exist to the CARS wavelength. Many approaches have been developed to reduce this background, such as polarisation control (Oudar et al., 1979; Yuratich and Hanna, 1977), time-delay (Volkmer et al., 2002; von Vacano and Motzkus, 2006), frequency modulation (Ganikhanov et al., 2006) and interferometric detection (Cheng, 2007; Evans et al., 2004; Müller and Zumbusch, 2007). The last has the advantage that the amplitude and phase are detected, where the amplitude is linear in the number (density) of the molecules. "
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    International Journal of Pharmaceutics 12/2010; 417(1-2):163-72. DOI:10.1016/j.ijpharm.2010.12.017 · 3.79 Impact Factor
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    • "In this scheme, the anti-Stokes pulses from the sample are mixed with pulses in the same frequency range from a local oscillator, resulting in phase-sensitive measurements. When broadband pulses are used in multiplex interferometric CARS schemes using spectral interferometry [31]–[33], the retrieved spectra resemble those acquired using spontaneous Raman spectroscopy. Alternatively, numerical algorithms using the maximum entropy method for discrimination of the resonant signal have been used [34], simplifying the optical set up, but at the expense of lengthening the processing time. "
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    • "This implies that the x ð3Þ r response displays a phase dependence as a function of vibrational frequency, whereas the spectral phase of x ð3Þ nr is flat throughout the vibrational spectral range of interest. Contrast improvement through CARS interferometry, for instance, is based on this phase difference [16] [17] [18] [19] [20]. Focus-engineered CARS (FE-CARS) also makes use of this phase difference to achieve image contrast enhancement. "
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    ABSTRACT: Focus-engineered coherent anti-Stokes Raman scattering (FE-CARS) microscopy is used to visualize microscopic samples with differential imaging contrast in both longitudinal and lateral directions. Multi-dimensional contrast is achieved by applying a one-dimensional π-phase step in the transverse beam profile of the Stokes beam. The observed longitudinal differential contrast results from fortuitous phase-matching at axial interfaces and is highly sensitive to the resonant part of the third-order susceptibility. Based on phase-sensitive recordings of the vibrational spectrum of dimethyl sulfoxide in the CH3-stretching range, it is shown that FE-CARS uniquely probes the spectral phase of the Raman bands of the sample.
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