161 W middle infrared ZnGeP₂ MOPA system pumped by 300 W-class Ho:YAG MOPA system

Abstract

We demonstrated a high-power <i>Q</i>-switched two-stage Ho:YAG master-oscillator power-amplifier (MOPA) system dual-end pumped by Tm:YLF lasers. A new method was introduced by rotating and swapping spatial axial directions of pump beams to improve the beam quality of the Ho:YAG oscillator and first-stage amplifier. Two parallel second-stage Ho:YAG amplifiers were employed to output high power. A total maximum average output power of 332 W at 2091 nm with pulse repetition frequency of 20 kHz was achieved. Then a <i>Z</i><i>n</i><i>G</i><i>e</i><i>P</i>₂ MOPA system was demonstrated using the Ho:YAG MOPA as the pump source. A maximum average output power of 161 W at 3-5 µm was obtained with 290 W incident Ho pump power, corresponding to beam quality factors <i>M</i>² of 3.42 and 3.83 for horizontal and vertical directions, respectively.