Flexible and stable optical parametric oscillator based laser system for coherent anti-Stokes Raman scattering microscopy.

The characteristics of a stable and flexible laser system based on a synchronously pumped optical parametric oscillator (OPO) is presented. This OPO can offer very stable operation with both approximately 1 ps and approximately 300 fs outputs over a broad wavelength range, i.e., 920-1200 nm. Combining the pump tuning with the OPO tuning, a total Raman range of 1900-5500 cm(-1) is accessible. For maximum spectral sensitivity, the CARS microsope based on the ps laser system is presented in detail. The lateral resolution of the microscope is diffraction limited to be about 390 nm. Fast wavelength switching (sub-second) between two Raman vibrational frequencies, i.e., 2848 cm(-1) for C--H aliphatic vibrations and 3035 cm(-1) for C--H aromatic vibrations is presented as an example, although this also extends to other Raman frequencies. The possibility of obtaining a multimodal imaging system based on the fs laser system is also discussed.