Silver thiogallate, singly resonant optical parametric oscillator pumped by a continuous-wave mode-locked Nd:YAG laser

We describe a silver thiogallate (AgGaS(2)) singly resonant optical parametric oscillator (OPO), synchronously pumped by a continuous-wave actively mode-locked Nd:YAG laser. The OPO is operated with a signal wavelength near 1.319 microm and an idler wavelength near 5.505 microm. At optimum output coupling, 100 mW of useful signal power and 6 mW of idler power are generated from 625 mW of pump power. The pump is mechanically chopped at a 32:1 duty cycle to prevent thermal lensing of the AgGaS(2) crystals. Pump depletion is as high as 63%. The signal has pulse widths ranging from 45 to 80 ps and spectral widths ranging from below 0.1 to 0.3 nm. The OPO signal can oscillate over a 2-mm range of round-trip cavity-length mismatch.