Optimizing laser active Q-switched through a few-layer WS2 passive saturable absorber

The main research content of this paper is to achieve active-passive dual-loss Q-switched based on a WS₂ saturable absorber (SA) with a thickness of 1.6 nm，thereby optimizing 1.06 &mu;m laser pulse output characteristics. The few layers of WS₂ nano-film material were prepared by combining electron beam evaporation (EBE) with chemical vapor deposition (CVD). The unsaturated absorption loss of the WS₂ sample is 7.3%, the modulation depth (<i>&Delta;T</i>) is calculated to be 19.2%, and the saturation power intensity(<i>I_sat</i>) was fitted to be 1.64 MW/cm². The prepared WS₂-SA successfully achieved passive Q-switched of the laser. When the pump power is 3 W, the maximum average output power, pulse width, pulse repetition rate, single pulse energy, and peak power are 752 mW, 390 ns, 400 kHz, 1.88 &mu;J, and 4.82 W, respectively-utilizing the saturable absorption characteristics of WS₂ to reduce the threshold of the acoustic-optic modulator (AOM) active Q-switched laser. Through comparative experiments, it is shown that the attributes of AOM+WS₂ active-passive Q-switched laser have been optimized. When the AOM frequency is 10 kHz, the narrowest pulse width of the dual-loss Q-switched laser is 16 ns, which is 30.4% less than the single AOM active Q-switched laser. The peak power of the active-passive Q-switched laser is 2.24 kW, which is 29.5% higher than the former. The pulse width compression and peak power increase are significant, which is beneficial for the instantaneous energy output of the laser.