Resonantly-diode-pumped 1645 nm Er:YAG MOPA laser with 4-pass amplifier

An Er:YAG master-oscillator (MO)/power amplifier (PA) system with a dual-end pumped, 4-pass, zig-zag, slab amplifier was experimentally and theoretically investigated. Both the Q-switched MO and PA were in-band diode-pumped at 1532 nm. With the MO seed pulse energy of 17 mJ, our MOPA yielded 70 mJ pulses with a duration of ∼ 80 ns at a pulse repetition frequency (PRF) of 1 kHz, thus delivering 70 W of average power at 1645 nm.