Growth and spectral properties of Cr ²⁺:ZnSe crystals for mid-infrared lasers

Cr ²⁺:ZnSe crystal with a volume of about 0.7 cm ³ was grown through PVT method, in which a temperature difference of 6-7°C between the source and growth ends at about 1000°C was applied for two weeks. The UV-VIS-NIR transmittance spectrum shows that there is a strong absorption peak at the wavelength of about 1770 nm. The calculated Cr ²⁺-doping concentration is around 10 ¹⁹ atoms/cm ³, which agrees well with that in the starting materials. The expecting Cr ²⁺-doping concentration is obtained at a relatively low temperature by PVT method. The fluorescence emission spectra of Cr ²⁺:ZnSe sample displays a strong emission peak at ~2400 nm with a well symmetric shape and a FWHM of ~600 nm. The room temperature emission lifetime is 5.52×10 ^-6 s. The results of data analysis indicates that the cross sections of absorption and emission of Cr ²⁺:ZnSe sample are 1.1×10 ^-18 cm ² and 2.3×10 ^-18 cm ², respectively.