Green-pumped optical parametric oscillator based on fan-out grating periodically-poled MgO-doped congruent LiTaO₃

We report a green-pumped optical parametric oscillator (OPO) based on periodically poled MgO-doped congruent lithium tantalate (MgO:cPPLT). Pumped at 532 nm by a frequency-doubled Q-switched Nd:YAG laser, and using a fan-out grating structure, the singly-resonant OPO provides continuous tuning across 689-1025 nm in the signal and 1106-2336 nm in the idler at room temperature by simple mechanical translation of the crystal. The tuning range can be further extended to 677 nm and 2479 nm in the signal and idler, respectively, by temperature tuning the crystal to 200°C. With a 29-mm-long crystal, the OPO generates 131 mW of average idler power at 1476.5 nm for an input pump power of 1.8 W at 25 kHz repetition rate, with a slope efficiency of 11.3%. Bulk damage in the MgO:cPPLT crystal has been observed for pump powers above ∼1.8  W, and at pump powers beyond ∼1.4  W under long-term operation. The passive power stability of the generated idler is 3.9% over 30 min, in a Gaussian spatial profile.