Continuously tunable, single-longitudinal-mode, pulsed mid-infrared optical parametric oscillator based on periodically poled lithium niobate

We present theoretical predictions and experimental results of a mid-infrar ed optical parametric oscillator (OPO) leased on periodically poled lithium niobate. An air-space intracavity etalon causes our OPO to oscillate on a single longitudinal mode. Continuous frequency tuning of this mode is achie ved by simultaneous adjustment of the etalon mirror spacing and the OPO res onator length with piezoelectric translators. We achieved 10 cm(-1) of cont inuous frequency tuning and more than 10 cm(-1) of mode-hop tuning. The OPO is pumped with 200 mu J/pulse by a seeded, 1-kHz, Q-switched Nd:YAG laser and provides as much as 10 mu J of energy in both the idler near the 3-mu m wavelength and in the signal near the 1.6-mu m wavelength. We obtained a r esolution of 0.01 cm(-1) with the idler when measuring the spectrum of the Q branch of the methane C-I-I stretch under Doppler-limited conditions. (C) 2000 Optical Society of America [S0740-3224(00)01207-8].