High-pulse-energy mid-infrared laser source based on optical parametric amplification in ZnGeP2

Nonlinear optical conversion of 1.064 microm pulses from a Q-switched Nd:YAG laser to the mid-infrared is demonstrated. The experimental setup is based on a two-stage master-oscillator/power-amplifier (MOPA) design with a KTiOPO(4) based MOPA in the first stage and a KTiOAsO(4)/ZnGeP(2) based MOPA in the second stage. The setup can be tuned to provide output at 8 microm or in the 3-5 microm wavelength region. We obtain more than 8 mJ at 8 microm, and up to 33 mJ at 3-5 microm. The measured beam quality factors are in the range M(2) =2-4 for both wavelength regions.