Temperature dependence of Cr:ZnSe active medium spectral and laser properties

Abstract

The interest in the development of coherent mid-infrared radiation sources is caused by its potential application in medicine, spectroscopy, laser remote sensing of the atmosphere, metrology, and in many other fields of interest. This study presents temperature dependence of spectral properties of Cr:ZnSe laser active medium in range of 78-380 K. The temperature influence on the absorption, fluorescence and oscillation spectra were investigated in detail. While heating the Cr:ZnSe crystal from 78K to 380 K, the absorption peak maximum has shifted for 65nm toward a shorter wavelength from 1813nm to 1748nm together with the absorption spectrum broadening from 262nm to 373nm and decreasing the absorption coefficient. The FWHM of the fluorescence spectrum was broadened from 280nm (2030-2310 nm) to 488nm (1896-2384 nm) when the temperature of active medium was increasing. Pulsed laser operation from Cr:ZnSe active medium longitudinally pumped by an Er:YLF laser at 1735nm was investigated. The temperature dependence of Cr:ZnSe laser output energy and oscillation spectrum were studied. The highest output energy was 3.84mJ at 78K which together with the FWHM pulse duration of μ200 s corresponds to the power of 19mW. The laser radiation emission was observed at three wavelength bands which intensity was changing during the increase of crystal temperature. However, the oscillation band around wavelength of ~2360nm occurred for all measured temperatures. As a result, by cooling the system, the wavelength of maximum absorption is being shifted to the longer wavelengths as well as the wavelength of maximum fluorescence spectrum intensity.