The phonon energy of rare earth doped silver halide crystals was investigated using Raman spectroscopy. An additional phonon vibrational mode was observed and attributed to localized defect vibrational modes. Good agreement was found between the measured and the predicted frequencies of the local modes. These additional low energy (65–80 cm−1) vibrational modes do not increase the thermal quenching of mid-IR luminescence of the rare earth ions in silver halide crystals. The rare earth doped silver halide crystals are suitable for the fabrication of mid-IR solid state lasers and fiber lasers due to their extremely low phonon energies.

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Novel surface treatments for an InAs 0.91 Sb 0.09 p-n junction grown on GaSb by MOCVD are proposed and demonstrated. Exposure of the p-n junction to argon ion plasma followed by etching with tartaric acid reduces the dark currents by five orders of magnitude. An additional reduction by two orders of magnitude in the dark current is achieved by illuminating the sample with white light. A mid-wavelength infrared photodetector based on the so treated p-n junction exhibits a high zero-bias resistance-area product (R 0 A) of 2.7 × 10 7 cm 2 and an internal quantum efficiency of 70% at 77 K. The measured BLIP temperature is 170 K and a high detectivity value (D * BLIP ) of 4.03 × 10 11 cm Hz 1/2 W −1 is observed at 3.7 μm. The surface treatment results indicate that the device performance is limited by bulk material properties.

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Infrared absorption and luminescence emission of cobalt doped silver halide crystals were investigated at room temperature and at low temperatures. A broad absorption band was observed in the near-infrared (1.4–2.5 µm) and a broad emission band in the middle-infrared (3.5–5.2 µm). The emission lifetime varied between 1.73 ms at low temperatures and 5 µs at room temperature. Based on the measured parameters and theoretical calculations, we believe that there is an excellent chance that these crystals would lase in the mid-IR. Moreover, it would be possible to extrude fibers from the crystals and obtain mid-IR fiber lasers.