Tunable Fe,Cr:ZnMgSe gain-switched mid-IR laser operating at room temperature

Abstract

The goal of this work was to design and investigate the gain switched new Fe,Cr:ZnMgSe laser operating at the room temperature. The pumping was provided by the electro-optically Q-switched Er:YAG laser with the oscillation wavelength of 2.937 µm which matching the absorption line of the Fe,Cr:ZnMgSe crystal. The Q-switched operation was obtained by the Brewster angle cut LiNbO 3 Pockels cell placed between the rear mirror and the laser active medium. The output radiation parameters were: the energy of 10 mJ, pulse duration of 120 ns, and repetition rate 1 Hz.The pump radiation was directed into the Fe,Cr:ZnMgSe crystal placed inside the 16 mm long hemi-spherical cavity formed by the dichroic pumping mirror (T = 86 % at 2.94 µm and R = 100% for 4 -5 µm) and the output coupler with the reflectance R = 95 % at 4 -5 µm and radius of curvature r = 500 mm. The maximum output Fe,Cr:ZnMgSe laser energy was 160 µJ corresponding the slope efficiency 4 % (with respect to absorbed energy). The generated radiation wavelength was 4.8 µm with the linewidth of 100 nm (FWHM). The output beam spatial profile was approximately Gaussian in both axes.Laser tuning properties were investigated by the Lyot filter (MgF 2 plate, 2 mm thick) inserted into the resonator providing the tuning range from 4.5 to 4.9 µm. The results were compared with the Fe:ZnSe crystal operated at the same conditions.