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: 3.29). 01/2005; 29(24):2923-5. DOI: 10.1364/OL.29.002923
Source: PubMed


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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    • "CARS [14,15] is much more efficient than spontaneous Raman spectroscopy [16–18], enabling faster, more sensitive analyses with less photo exposure. CARS circumvents the need for extrinsic labels, allowing observation of dynamic phenomena for which tags are not available. "
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    • "CARS imaging formulates contrast by probing resonances from specific chemical bonds in unstained samples, enabling its chemical selectivity. Its coherent nature further renders CARS signal several orders of magnitude stronger than the conventional Raman signal, thus offering video-rate imaging speed [16,17]. Therefore, this imaging modality has been successfully applied to a variety of biomedical applications, including the imaging of viruses, cells, tissues and live animals, as well as drug delivery [12,18–25]. "
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    • "On the one hand, the nonlinear nature of the process demands short pulses (ps or fs) with high peak power, and on the other hand a system with good tunability or a large bandwidth is necessary for spectroscopic measurements. Typical CARS systems based on optical parametric oscillators [5, 6] or synchronized Ti:Sapphire lasers [7,8] have been successful for imaging lipids, myelin and water [4, 9] (for a review see [10]) but their relatively slow tunability has hampered their use in spectroscopy. Broadband methods based on transform-limited ultrashort pulses [11–13] or continuum generation [14] have been successful for spectral imaging of optically thin systems. "
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