A 70.7% slope-efficiency, mid-infrared tunable Fe:ZnSe laser gain-switched by a high-energy 3.47 μm potassium titanyl arsenate optical parametric oscillator and amplifier

Abstract This paper presents the first demonstration of a mid-infrared (MIR) Fe:ZnSe laser gain-switched by a non-critical phase-matched potassium titanyl arsenate optical parametric oscillator and amplifier at 3.47 μm. A novel improvement in slope efficiency was achieved by this new pump source, which significantly promoted the quantum efficiency compared to the conventional pump wavelength near 2.9 μm. The slope efficiency of 70.7% is a new record for Fe:ZnSe lasers with an output energy of 86 mJ and pulse width of 6.7 ns at 10 Hz. The output wavelength was tunable from 3.9 to 4.5 μm by changing the crystal’s temperature from 80 to 300 K. The influence of the pump beam size on transverse parasitic oscillation and crystal damage was investigated considering the dynamic absorption effect in Fe:ZnSe. This unique design provides an advancing and promising method of high-energy and short-pulse-width MIR lasers for extreme applications requiring both high-energy density and high-peak-power intensity.