High repetition rate mid-infrared laser source

An efficient, high-power mid-infrared laser source based on ZnGeP2 (ZGP) optical parametric oscillator (OPO) is presented. Using a Q-switched Ho:YAG laser as the pump source a total output power of 10.6 W was obtained in the 3-5 mu m band at 10 kHz and 8.5 W at 20 kHz. The Ho:YAG laser was pumped by two diode-pumped polarization coupled Tm:YLF lasers. Optical-to-optical efficiency achieved is >8.8% (laser-diode 792 nm to mid-IR 3-5 mu m). With a commercial PtSi infrared camera (256 x 256 pixel focal plane array, 24 mu m pitch) the pointing stability of Ho pump, signal and idler beam was measured to be better than 30 mu rad. Whilst propagating the OPO beams over similar to 100 m, little absorption for the idler beam was observed, resulting in a significant higher peak-to-peak value of +/- 22%, whereas the peak-to-peak stability of the signal pulses remained unchanged (+/- 13%).