Search

Cr 2+ :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 Cr 2+ -doping level in the crystals. A simple theoretical model has been developed for evaluation of the thermal diffusivity of Cr 2+ 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 910°C. 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 900°C for 1.75 days.

Characterization studies of Cd1−xZnxTe (0

We report the investigation by photoluminescence lifetime measurements of the near-IR emissions from a series of chromium-doped ZnSe samples, correlated to their preparation conditions. The samples were polycrystalline or single crystals prepared by post growth diffusion doping or single crystals doped during growth by the physical vapor transport method. Room temperature lifetime values between 6 and 8 μs were measured for samples with Cr 2+ concentrations from low 10 17 to high 10 18 cm -3 range. Lifetime data taken down to 78 K was found to be rather temperature independent, reconfirming previous reports indicating a quantum yield of the corresponding emission of close to 100% at room temperature. A strong decrease in the room temperature lifetime was found for chromium concentrations higher than 10 19 cm -3 .

The preparation and thermophysical properties of AgGaTe 2 crystals are reported. The synthesis from pure elements was performed in a rocking oven and scanning electron microscopy and energy dispersive X-ray elemental analysis show the presence of additional phases. From simultaneous differential calorimetry and thermogravimetric analysis (SDT) measurements we have found that AgGaTe 2 melts at 725.7°C, with a heat of fusion of 104.8 J/g −1 . High temperature powder X-ray diffraction data confirmed the chalcopyrite structure and yielded the thermal expansion coefficients along the a - and c- axes to 500°C. Heating above that temperature, under inert gas flow, causes the material to sublime incongruently and produce a film of gallium rich surface. Experimental values of thermal diffusivity and estimates of the thermal conductivity values are also presented.

This paper reviews some of the progress obtained in the understanding of defects in detector grade cadmium zinc telluride material (CZT). Several techniques have been utilized to elucidate some of the issues related to compositional uniformity, effects of precipitates, grain boundaries, and surface defects related to mechanical and chemical treatments. In few cases, special mapping capabilities had to be developed to allow correlations with detector performance.

Solid-state tunable laser sources in the mid-IR region have been recently investigated for their potential in remote sensing applications. Room temperature lasers based on single crystals of chromium-doped CdSe are particularly interesting due to their broad band tunability beyond 2 lm spectral region. In this study, we have grown doped single crystals by the high-temperature gradient freezing solution technique, using selenium as the solvent. Crystals of 1.2 cm in diameter and up to 7 cm long, cracks and precipitates free could be obtained. The e!ective segregation coe$cient of Cr2‘ ions along the ingot was evaluated. Room temperature emission lifetime values of 3.0}4.5 ls were measured. ( 2000 Published by Elsevier Science B.V. All rights reserved.