Fe2+:ZnSe laser is one of the research hotspots of new mid-infrared solid-state lasers with a wide application prospect in the fields of atmospheric monitoring, space remote sensing, laser medical, laser radar and so on. It has broad bandwidth tunability and high energy output characteristics.

In a study published in Optics and Laser Technology, a research group led by PAN Qikun and his student XU Fei from Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP) of the Chinese Academy of Sciences (CAS) proposed a new theoretical model of mid-infrared gain switched pulsed iron-doped ZnSe laser.

Considering the factors of instantaneous pump efficiency, excited-state absorption, and temperature, researchers established a theoretical model of gain-switched pulsed Fe2+:ZnSe laser by analyzing the configuration coordinate model of Fe2+.

Simulation results show the kinetic characteristics of gain-switched pulsed Fe2+:ZnSe laser. The primary spike pulse and relaxation oscillation phenomenon of pulse waveform is presented in theory, which agree well with the experimental result. The correctness of the theoretical model is verified.

Researchers also further simulated the main factors of temperature, Fe2+ doping concentration, and output coupler reflectivity that affect the output of the pulsed Fe2+:ZnSe laser.

Temperature is found to have a significant influence on the efficiency of pulsed Fe2+:ZnSe laser, and the laser efficiency is higher at 77 K than at 294 K. At lower Fe2 + concentrations, the delay between the laser and the pump light is large and the laser efficiency is low.

With an increase in the output coupler reflectivity, the efficiency of the pulsed Fe2+:ZnSe laser adopted a quadratic curve. In addition, the pump threshold, pulse build-up time, and laser peak power intensity are found to be inversely proportional to the output coupler reflectivity.

The study will make a significant contribution to the literature because "it provides a theoretical basis for the structural optimization of pulsed Fe2+:ZnSe laser for improving the output efficiency", according to the researchers.