Enhanced 2.7 µm wavelength sub-80 ns pulse generation via iron-chromium co-doped ZnS polycrystalline

Zinc-sulfide (ZnS) polycrystalline co-doped with Cr²⁺ and Fe²⁺ ions, when used as a saturable absorber (SA), exhibits a longer recovery time and a larger excited state absorption cross-section compared to Fe:ZnS polycrystalline, due to the sensitizing effect of co-doping. The energy level structure and energy transfer process of Fe,Cr:ZnS polycrystalline were analyzed. A 2.7 µm wavelength passively Q-switched (PQS) pulsed laser was simulated and experimentally tested. The experiment achieved a narrower pulse width of 78 ns with a repetition rate of 44 kHz, compared to the Fe:ZnS SA Q-switched laser. The experimental results closely matched the simulation in terms of pulse profile, repetition rate, and pulse width. To the best of our knowledge, this is the first time that Fe,Cr:ZnS polycrystalline is used as a SA to realize PQS lasing. The superior characteristics of co-doped crystals as SAs have also been highlighted.