Theoretical and experimental characterization of coherent anti-Stokes Raman scattering microscopy

We present a systematic characterization of coherent anti-Stokes Raman scattering (CARS) microscopy. CARS signal generation in a heterogeneous sample under a tight-focusing condition is formulated by the Green's function method. The CARS radiation pattern and the forward- and backward-detected CARS signals from a three-dimensional Raman scatterer are calculated. The coherent nature of CARS image formation and its consequences for image contrast and spatial resolution are investigated. Experimental implementations of CARS microscopy with collinearly copropagating and counterpropagating excitation beams, forward and backward data collection, and polarization-sensitive detection are described. Finally, CARS images of unstained live cells with forward detection, epidetection, and polarization-sensitive detection are presented and compared. (C) 2002 Optical Society of America.