A 71 mJ, 300 Hz mid-infrared source based on ZnGeP₂ MOPA system

We demonstrated a 71 mJ mid-infrared ZnGeP 2 (ZGP) master oscillator power amplifier (MOPA) system that operated at the pulse repetition frequency of 300 Hz. A 2090.6 nm electro-optical Q-switched holmium: yttrium -aluminum-garnet MOPA system with a total energy of 138.3 mJ was used as the pump source of the ZGP-MOPA system. First, based on a ZGP optical parametric oscillator, a mid-infrared laser output of 1.3 mJ was obtained in the state of low-energy pumping. The corresponding beam quality factor M 2 was 2.01 x 2.10 (horizontal directions x vertical directions). After two-stage amplification, a mid-infrared laser of 71 mJ was obtained. The pump energy and seed energy of the second ZGP optical parametric amplifier were 92.7 mJ and 23 mJ, the corresponding slope efficiency was 70.3 %. At the maximum output energy level, the pulse width of the mid-infrared laser was 14.6 ns, and the beam quality factor M 2 was 3.96 x 3.75.