title: Lorentzian amplitude and phase pulse shaping for nonresonant background suppression and enhanced spectral resolution in coherent anti-Stokes Raman scattering spectroscopy and microscopy.
abstract: Femtosecond coherent anti-Stokes Raman scattering (CARS) spectroscopy offers several advantages over spontaneous Raman spectroscopy due to the inherently high sensitivity and low average power deposition in the sample. Femtosecond CARS can be implemented in a collinear pump/probe beam configuration for microspectroscopy applications and has emerged as a powerful technique for chemical imaging of biological specimens. However, one serious limitation of this approach is the presence of a high nonresonant background component that often obscures the resonant signals of interest. We report here an innovative pulse-shaping method based on Lorentzian amplitude and phase spectral modulation of a broadband femtosecond probe pulse that yields spectra with both high spectral resolution and no nonresonant background. No further mathematical analysis is needed to extract Raman spectra. The utility of the proposed method for CARS microscopy is demonstrated using a mixture of polystyrene and latex beads, as well as dry-fixed embryonic stem cells.
authors.affiliation: Michael Smith Laboratories, The University of British Columbia, 2185 East Mall, Vancouver, BC, V6T 1Z4, Canada.
authors.forename: Stanislav O
authors.initials: SO
authors.lastname: Konorov
authors.forename: Michael W
authors.initials: MW
authors.lastname: Blades
authors.forename: Robin F B
authors.initials: RF
authors.lastname: Turner
mesh_terms: D000818:Animals; D002460:Cell Line; D053595:Embryonic Stem Cells / Q000166:cytology; D004867:Equipment Design; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D008853:Microscopy / Q000295:instrumentation / Q000379:methods*; D013059:Spectrum Analysis, Raman / Q000295:instrumentation / Q000379:methods*