Stable high-power Er:YAG ceramic single-frequency laser at 1645 nm

A stable high-power single-frequency laser at 1645 nm from a monolithic Er:YAG ceramic nonplanar ring oscillator (NPRO) was demonstrated. 10.7 W single-frequency laser output was obtained with a slope efficiency of 61.2% and an optical efficiency of 52.1% with respect to incident pump power. The laser always stably operated in single-frequency mode with the pump power increasing from threshold to maximum pump power. When the crystal's set temperature changed from 17.2°C to 26.6°C, the Er:YAG ceramic NPRO had stable single-frequency laser output, and the widest continuous tuning range without mode-hoping was 4.5 GHz. The linewidth of the single-frequency laser was 5.75 kHz. The beam quality M² factors were 1.23 and 1.24 in x and y directions, respectively.