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

Abstract

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&#x0025;, 0.093 GW/cm² and 37.71&#x0025;, respectively. By incorporating the as-prepared saturable absorber mirror in a single-mode Er^3&#x002B;-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 <inline-formula> <tex-math notation="LaTeX">$1.04 ~\mu \text{s}$ </tex-math></inline-formula> and 93.10 kHz, respectively. The corresponding pulse energy was <inline-formula> <tex-math notation="LaTeX">$10.02 ~\mu \text{J}$ </tex-math></inline-formula> and the slope efficiency was 18.1&#x0025;. 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-<inline-formula> <tex-math notation="LaTeX">$2.80 ~\mu \text{m}$ </tex-math></inline-formula> waveband, and the Q-switched laser presents threefold and twofold increase in output power and pulse energy, respectively, over previously reported values achieved from &#x007E;3-<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> 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.