Noncritical phase-matched lithium triborate optical parametric oscillator for high resolution coherent anti-stokes Raman scattering spectroscopy and microscopy

An efficient, widely tunable, narrow-bandwidth, green-pumped, noncritical phase-matched lithium triborate based optical parametric oscillator (OPO) is applied to coherent anti-Stokes Raman scattering (CARS) spectroscopy and microscopy. The tunable signal beam (740–930 nm) of the OPO is combined with the fundamental of a Nd:YVO4 pump laser (1064 nm, 15 ps) to obtain high resolution vibrational spectra of molecules around the CH vibrational stretch (2700–3100 cm−1). The straightforward and convenient tunability of the OPO is demonstrated by CARS microscopy for the identification of different polymer microparticles on the same substrate.