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A highly efficient 3.2 μm optical parametric oscillator pumped by a passively Q-switched Nd:YVO4 laser

We describe a compact all-solid-state singly resonant optical parametric oscillator (SRO) based on a Cr4+: YAG Q-switched Nd:YVO4 laser. The SRO is based on periodically poled MgO:LiNbO3 (PPMgLN) as the nonlinear material. By exploiting a 35 mm PPMgLN crystal, we achieved the SRO operation threshold at a pump power of only 140 mW. At 1.78 W of pump laser with a pulse width of 10 ns and a repetition of 50 kHz, 360 mW average power at 3.2 μm and a mid-infrared conversion efficiency of 20% were achieved.