Crystal Growth and Effects of Annealing on Optical and Electrical Properties of Mid-Infrared Single Crystal LiInS2

Single crystal LiInS2 (LIS) is a promising candidate for mid-infrared (MIR) frequency conversion to obtain MIR laser output. Large-sized LIS crystals with a diameter of 16 mm and a length of 50 mm were grown by the modified Bridgman method. The as-grown LIS crystals were annealed in different atmospheres, and the effects of annealing on the electrical and optical properties were studied in detail. The visible-near-infrared and MIR transmission spectra of the crystals were studied before and after annealing in different atmospheres. The experimental results indicate that the optimal annealing conditions for a grown crystal are to use an atmosphere of LIS vapor at 700 °C for 160 h. The electrical properties were investigated before and after annealing in the LIS vapor atmosphere. After proper postgrowth annealing, the quality of the crystal was significantly improved, which resulted in an increase in the damage threshold from 0.9 to 1.2 J/cm2.