Parametric generation of light in sodium vapor in a synchronously pumped resonator

An investigation was made of a resonant optical parametric oscillator based on the resonant third-order nonlinearity in sodium vapor. Synchronous bichromatic pumping was provided by picosecond optical pulses of good spectral quality. Dependences of the main parameters of the output radiation of a four-photon optical parametric oscillator on the sodium concentration and on the optical resonator length were obtained.