PtSe2 as a Wideband Saturable Absorber for Passively Q-Switched High-Power Mid-Infrared Fiber Laser

We report a transition metal dichalcogenides-PtSe2 Q-switched single-mode fiber laser operating at 2783.2 nm with a nearly watt-level average output power. We made a PtSe2 coated highly reflective gold mirror to serve as a saturable absorber mirror. The modulation depth, saturable intensity and non-saturable loss of our PtSe2 sample were measured to be 10.2%, 0.093 GW/cm(2) and 37.71%, respectively. By incorporating the as-prepared saturable absorber mirror in a single-mode Er3+-doped zirconium fluoride fiber laser, stable Q-switched laser pulses were obtained with a maximum average power of 932.7 mW. The pulse duration and repetition rate were 1.04 mu s and 93.10 kHz, respectively. The corresponding pulse energy was 10.02 mu J and the slope efficiency was 18.1%. By employing a plane ruled grating in the resonator, we also investigated the operating wavelength range of the PtSe2-coated mirror. A continuously wavelength-tunable Q-switched laser was obtained from 2733.0 nm to 2803.0 nm. To the best of our knowledge, this is the first demonstration of PtSe2 working as a saturable absorber for the 2.73-2.80 mu m waveband, and the Q-switched laser presents threefold and twofold increase in output power and pulse energy, respectively, over previously reported values achieved from similar to 3-mu m single-mode Q-switched fiber lasers enabled by two-dimensional materials. The results indicate that PtSe2 is an excellent wideband optical switch for high-power broadband mid-infrared laser pulses generation.