Coherent anti‐Stokes Raman micro‐spectroscopy using spectral focusing: theory and experiment

Abstract Coherent anti‐Stokes Raman scattering (CARS) microscopy using linearly chirped femtosecond laser pulses and spectrally and time‐integrated detection is discussed both theoretically and experimentally. By matching the linear chirp of Stokes and pump pulses, the spectral resolution is reduced to the Fourier limit of the chirped pulse duration (spectral focusing). We discuss the effect of the time‐ordering of Pump and Stokes pulses on the signal strength and selectivity, and give analytical expressions for the relevant quantities. We consider linear chirp obtained by glass elements of known group‐velocity dispersion, and analyze the limit of the spectral resolution by higher order glass dispersion. Experiments corroborating the theory are presented, using 100 fs laser pulses, SF57 glass elements, and polystyrene beads as test samples. Copyright © 2009 John Wiley & Sons, Ltd.