Material preparation and infrared spectroscopy of Cr 2+ doped II-VI semiconductor windows and crystals for mid-infrared laser applications

In this thesis the preparation and infrared spectroscopy of Cr diffusion doped zinc and cadmium chalcogenides including ZnSe, CdTe, Cd0.96Zn0.04Te, Cd0.90Zn0.10Te, Cd0.80Zn0.20Te, and ZnTe are reported. The materials were prepared by a thermal diffusion process controlled by temperature and time. Cr2+ doped II-VI semiconductors continue to be of significant interest as gain media in mid-infrared (2-3 mum) solid-state lasers. Various samples of polycrystalline windows of Cr2+:ZnSe and Cr 2+:CdTe were prepared with Cr2+ peak absorption coefficients ranging from ∼ 0.8 cm-1 to 28.7 cm-1. Commercial CrSe powder of 99.5 % purity was used as the dopant source. The Cr2+ room-temperature decay time varied between 5-6 mus for Cr:ZnSe and 2-3 mus for Cr:CdTe. Time-resolved emission studies revealed the effect of dopant concentration quenching on the mid-infrared emission for doping concentrations above ∼1x1019cm-3. By increasing the Zn composition within the CdXZn1-XTe series, a wavelength shift of the Cr2+ infrared absorption and emission spectra to shorter wavelengths was observed.