Highly Efficient Continuous-Wave and Passively Q-Switching 2.8- $\mu$ m Er:YSGG Laser

Highly efficient continuous-wave (CW) and passively Q-switching Er:YSGG lasers at around 2.8 μm were demonstrated. In the CW regime, a maximum output power was 514 mW with the dual-wavelength of 2795 and 2825 nm. The slope efficiency and optical-optical conversion efficiency were as high as 31% and 23%, respectively. Adopting black phosphorus as saturable absorber, a maximum output power of the passively Q-switched Er:YSGG laser was 240 mW, with a corresponding slope efficiency up to 15.8%. The shortest pulse duration was 293 ns, and the repetition rate was 109.1 kHz. The results indicated that Er:YSGG crystal would be a promising mid-infrared gain medium for high-efficiency laser operation.