Thermal diffusion of Cr2+ in bulk ZnSe

Cr2+:ZnSe is now known as a room-temperature widely tunable solid-state mid-infrared laser material. Optimization of laser performance requires first and foremost optimization of the Cr2+-doping level in the crystals. A simple theoretical model has been developed for evaluation of the thermal diffusivity of Cr2+ ions in bulk ZnSe single crystals and polycrystalline window materials, from optical absorption measurements in the 1200-2800 nm spectral region. Sputtered metallic chromium and powders have been used as dopant sources. Diffusion appears to be faster in polycrystalline materials than in single crystals for annealing temperatures below 910degreesC. The activation energy, which is lower in polycrystals, depends on the nature of the dopant source. For mid-IR laser application, the model predicts for example, non-negligible optical losses due to passive self-absorption in the 2000-3000 nm spectral region for chromium-doped polycrystalline materials after annealing at temperatures above 900degreesC for 1.75 days. (C) 2002 Elsevier Science B.V. All rights reserved.