High power widely tunable mid-IR (5-7.2 gm) ZnGeP₂ optical parametric oscillator pumped by a 2.09 gm laser

A high-power widely tunable nanosecond (ns) mid-infrared (mid-IR) optical parametric oscillator (OPO) in a ZnGeP2 crystal has been demonstrated. The OPO is pumped by a Q-switched 2.09 mu m Ho: YAG laser with 10 kHz repetition frequency. Based on optimizing the parameters of ZGP-OPO system, a maximum idler power as high as 5.47 W is achieved at 5.05 mu m with photon conversion efficiency of up to 46.4 %. By rotating the angle of the ZGP crystal, the idler tuning region across from 5 to 7.2 mu m is realized, with >1 W of idler power over almost the entire tuning region. The idler operation displays high pulse stability with peak to peak amplitude fluctuation less than +/- 2.8 % in near-Gaussian spatial mode.