Modeling of sub-nanosecond Fe:ZnSe mid-IR gain-switched laser operating at room temperature

Sub-ns pulse mid-IR lasers have many important scientific and industrial applications including optical parametric chirped-pulse amplification pump sources and material processing. Unfortunately, effective sub-ns mid-IR laser sources are limited. In this study, we report on the numerical simulation and optimization of a spike-like oscillation dynamic in room temperature mid-IR Fe:ZnSe lasers operating at 4.4 µm to obtain sub-ns relaxation oscillation pulses from 15 ns Q-switched Er:YSGG pump pulses. Optimizing cavity length, iron ion concentration, and output coupler reflectivity yielded a single 588 ps pulse (FWHM) with an output energy of 1.7 mJ. This was achieved using a pump pulse energy of 17mJ (140 mJ/cm²) at a 2.79 μm wavelength.