160 mJ cryogenic Ho:YLF laser with unstable resonator

The properties of Ho:YAG for high energy operation improve dramatically at low temperatures, and we have exploited this effect in a cryogenically cooled Ho:YLF laser for high pulse energies at 2 μm. The laser is pumped by 60 W from a Tm-fiber laser emitting at 1940 nm. In low repetition rate Q-switched operation we are able to generate 160 mJ at 2.05 μm from 10 ms pump pulses, with a slope efficiency of 43 %, and a considerable scaling potential.