Fibre-laser-pumped mid-infrared source

We present a simple design for efficient generation of high average power in the 3-5 μm wavelength range. Using a 15 W thulium-doped fibre laser to pump a Q-switched 2.1 μm Ho:YAG laser, we obtain 9.2 W average output power with excellent beam quality. The 2.1 μm output is used to pump a ZnGeP₂-based OPO, resulting in 4.6 W average output power in the 3.6-5.2 μm range with beam quality M² < 1.4.