Theoretical characteristics of mid-infrared gain switched pulsed iron-doped ZnSe laser

• The theoretical model of gain-switched pulsed Fe 2+ :ZnSe laser was established. • Factors such as instantaneous pump efficiency and excited-state absorption were considered. • Primary spike pulse and relaxation oscillation phenomena of Fe 2+ :ZnSe laser was revealed. • The key factors affecting the output of the pulsed Fe 2+ :ZnSe laser are simulated. We report a four-level theoretical model revealing the laser kinetics of a gain-switched pulsed Fe 2+ :ZnSe laser that is established for the first time, to the best of our knowledge. The experimental results agree with the theoretical primary spike pulse and relaxation oscillation phenomenon of pulse. Furthermore, the effects of temperature, doping concentration, and the output coupler reflectivity on the performance of the pulsed Fe 2+ :ZnSe laser are simulated using the proposed model. The simulated results indicate that the laser efficiency is higher at low temperature and high Fe 2+ concentrations, and the optimal output coupler reflectivity is ∼23% at 77 K.