B-AsP as the saturable absorber for a mid-infrared 3 µm nanosecond laser

Black arsenic-phosphorus (B-AsP) has better stability than traditional black phosphorus (BP), and it was utilized to modulate a mid-infrared (mid-IR) 3 µm laser for what we believe to be the first time. The linear and nonlinear absorption characteristics of B-AsP at 3 µm were also investigated. The maximum continuous wave (CW) output power of the Er: SrF2 laser was 240 mW with an absorbed pump power of 2.87 W, resulting in a corresponding slope efficiency of 8.1%. During passively Q-switched (PQS) experiments, a laser pulse with a minimum duration of 188 ns was successfully generated at a repetition rate of 78 kHz, and the relevant single-pulse energy was 2.0 µJ. To the best of our knowledge, this is the narrowest passively Q-switched pulse for Er:SrF 2 crystal laser. Our results indicate that B-AsP SA was a promising candidate to be the optical modulator in the mid-IR wavelength range.