High power cryogenic Ho:YAG laser

We have improved significantly the brightness of cryogenic Ho:YAG, reporting up to 65 W output power with a beam quality of M2 <1.3 and a slope efficiency of 71%. The laser emission was ~2 nm wide and centered at 2097.5 nm. This result demonstrates the scalability of both the narrow-line thulium fibre pump laser and the cryogenic laser head.