We demonstrated a high-power Q -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 Z n G e P 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 M 2 of 3.42 and 3.83 for horizontal and vertical directions, respectively.

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We firstly demonstrated a tunable 2.1 µm pumped mid-infrared type-II phase-matching B a G a 4 S e 7 (BGSe) optical parametric oscillator (OPO). A signal tuning range of 3.82–3.99 µm was achieved. With a signal light produced by the BGSe OPO serving as seed, the Z n G e P 2 (ZGP) optical parametric amplifier (OPA) was first introduced. A 4.35 W mid-infrared laser was obtained in the novel type-II BGSe OPO with a ZGP OPA system, which was pumped by a 24 W 1 kHz Q -switched Ho:YAG laser. The beam quality factor M 2 of the whole system is ∼ 2.3 , which is over a 50% promotion on the previous M 2 results of single BGSe OPO.

We demonstrated a high-power long-wave infrared optical parametric oscillator at 9.8 µm based on a type-I phase-matching Z n G e P 2 crystal. By using a Q -switched 2091 nm Ho:YAG laser with pulse repetition frequency of 10 kHz as the pump source, the maximum average output power of 3.51 W at 9.8 µm was achieved with incident pump power of 90 W, corresponding to a slope efficiency of 4.81% and conversion efficiency at maximum pump power of 3.9%. The pulse width of 19.6 ns and linewidth of 142 nm were obtained at maximum output level. In addition, the beam quality factor M 2 was measured to be ∼ 2.2 .