1886-nm mode-locked and wavelength tunable Tm-doped CaF2 lasers

A 3 at.% Tm-doped CaF2 crystal was grown successfully and used as a gain medium. A high-efficiency continuous-wave laser and wide tuning performance were demonstrated in this crystal, and passive mode-locking laser operation was realized for the first time, to the best of our knowledge. For continuous-wave operation, the maximum output power was 2.71 W with a high slope efficiency of 70.3%. Using a quartz birefringent filter, a continuous tuning range of approximately 190 nm was observed in the tuning mode. In addition, a passively mode-locked Tm3+:CaF2 laser emitting at 1886.8 um was achieved with a semiconductor saturable absorber mirror. At an absorbed pump power of 2.65 W, a pulse duration with tens of picoseconds was obtained at a pulse repetition rate of 96.35 MHz. (C) 2018 Optical Society of America