Diode-pumped Cr-doped ZnMnSe and ZnMgSe lasers

Chromium ions Cr 2+ are known to have good fluorescence properties in the mid-infrared spectral region around the wavelength of 2.5 μm. The aim of this study was the investigation of new laser crystal materials – Zn 0.95 Mn 0.05 Se, Zn 0.70 Mn 0 .30 Se, and Zn 0.75 Mg 0.25 Se doped by Cr 2+ ions and comparison of their spectral and laser characteristics. The spectroscopic parameters as absorption and fluorescence spectra as well as lifetimes were measured. As optical pumping the laser diode generating radiation at the wavelength of 1.69 μm (pulse repetition rate 10 Hz, pulse width 2 ms) was used. The longitudinal-pumped resonator was hemispherical with an output coupler radius of curvature 150 mm. The laser emission spectra were investigated and the highest intensity of emitted radiation was achieved at wavelengths 2451 nm, 2469 nm, and 2470 nm from the Cr:Zn 0.95 Mn 0.05 Se, Cr:Zn 0.70 Mn 0.30 Se, and Cr:Zn 0.75 Mg 0.25 Se laser systems, respectively. The input-output characteristics of laser systems were measured; the maximum output peak power 177 mW was obtained for Cr:Zn 0.95 Mn 0.05 Se laser system with slope efficiency of 6.3 % with respect to absorbed peak power. The output peak power as well as output beam spatial structure were stable during measurements. For the selection of the lasing wavelength, the single 1.5 mm thick quartz plate was placed at the Brewster angle inside the optical resonator between the output coupler and laser active medium. This element provided the tuning in the wavelength range 2290–2578 nm, 2353–2543 nm, and 2420–2551 nm for Cr:Zn 0.95 Mn 0.05 Se, Cr:Zn 0.70 Mn 0.30 Se, and Cr:Zn 0.75 Mg 0.25 Se, respectively. The obtained spectral FWHM linewidth of the individual output radiation was ~ 10 nm. A comparison with previously measured Cr:ZnSe laser system was added in the end