Highly efficient low-threshold tunable all-solid-state intracavity optical parametric oscillator in the mid infrared

An intracavity critically phase-matched optical parametric oscillator (OPO) was demonstrated with a LiNbO(3) crystal placed inside the resonator of a diode side-pumped Q-switched Nd:YAG laser. The OPO acted as a singly resonating cavity on the signal with a threshold below 10 MW/cm(2). Output energy as high as 640 microJ was observed at the idler wavelength of 3.7 microm, which corresponds to a conversion efficiency of 1.8% from diode light to idler light. Tunability over the wavelength range 3.3-4.15 microm was obtained by rotation of the LiNbO(3) crystal.