OPO CARS: coherent anti-Stokes Raman spectroscopy using tunable optical parametric oscillators injection-seeded by external-cavity diode lasers

Coherent anti-Stokes Raman spectroscopy (CARS) is performed on nitrogen gas using the signal wave from a pulsed β-barium borate optical parametric oscillator (OPO), which has a passive ring cavity and is injection-seeded at its idler wavelength by a single-mode, external-cavity diode laser. The observed CARS linewidths are consistent with an optical bandwidth of 0.01 cm−1 for the continuously tunable OPO signal radiation. Moreover, injection seeding with two diode lasers generates two-line rovibrational CARS spectra giving thermometric information on a single-shot basis. The utility of these OPO CARS methods for combustion diagnostics is indicated.