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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    ABSTRACT: Microalgae are extensively researched as potential feedstocks for biofuel production. Energy-rich compounds in microalgae, such as lipids, require efficient characterization techniques to investigate the metabolic pathways and the environmental factors influencing their accumulation. The model green alga Coccomyxa accumulates significant amounts of triacylglycerols (TAGs) under nitrogen depletion (N-depletion). To monitor the growth of TAGs (lipid) in microalgal cells, a study of microalgal cells (Coccomyxa sp. C169) using both spontaneous Raman and coherent anti-Stokes Raman scattering (CARS) spectroscopy and microscopy were carried out. Spontaneous Raman spectroscopy was conducted to analyze the components in the algal cells, while CARS was carried out to monitor the distribution of lipid droplets in the cells. Raman signals of carotenoid are greater in control microalgae compared to N-depleted cells. Raman signals of lipid droplets appear after N-depletion and its distribution can be clearly observed in the CARS microscopy. Both spontaneous Raman spectroscopy and CARS microscopy were found to be suitable analysis tools for microalgae.
    Biomedical Optics Express 11/2012; 3(11):2896-906. DOI:10.1364/BOE.3.002896 · 3.65 Impact Factor
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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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    Biomedical Optics Express 08/2011; 2(8):2160-74. DOI:10.1364/BOE.2.002160 · 3.65 Impact Factor
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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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