Efficient, low threshold, cryogenic Ho:YAG laser.

We report the development of an efficient, liquid-nitrogen conduction cooled Ho:YAG slab laser with good beam quality. Detailed measurements resolving the structure of the 1900-1911 nm absorption band in Ho:YAG at 77 K are presented. Stress-free conduction cooled mounting of the Ho:YAG slab was demonstrated and the resulting laser operated with a large mode volume of 42 mm3, a slope efficiency of 75% and a threshold of 0.84 W. To our knowledge this corresponds to the lowest reported threshold intensity for a Ho:YAG laser.