Phase Transitions and Nonlinear Optical Property Modifications in BaGaSe.

Phase transitions can change the crystal structure and modify the physical properties of crystals. In this work, we investigate the phase transition behavior in BaGaSe, an important middle infrared (mid-IR) nonlinear optical (NLO) crystal, in the temperature range from room temperature to 1173 K. Interestingly, the BaGaSe crystal undergoes a reversible ferroelastic phase transition at = 528 K, resulting in the presence of a newly discovered phase (γ-phase) at the higher temperature.

Negative thermal expansion and electronic structure variation of chalcopyrite type LiGaTe.

The LiGaTe crystals up to 5 mm in size were grown by the modified Bridgman-Stockbarger technique and the cell parameter dependence on temperature in the range of 303-563 K was evaluated by the X-ray diffraction analysis. The thermal behavior of LiGaTe is evidently anisotropic and a negative thermal expansion is found along crystallographic direction with coefficient -8.6 × 10.

Crystal Growth, Structure, and Optical Properties of LiGaGe2Se6.

Large single crystals of LiGaGe2Se6 were grown, and their structure and linear optical properties were studied. According to XRD results there is some disorder because of the Li ion fluctuation and their redistribution along two cationic sites. The shape of the fundamental absorption edge versus temperature was analyzed, and direct band gap values were estimated from the Tauc plots.

Frequency doubling of CO2 laser radiation at 10.6 microm in the highly nonlinear chalcopyrite LiGaTe2.

Type-I phase matching for second-harmonic generation at 10.6 microm in LiGaTe(2) is demonstrated by using a tunable single-frequency continuous-wave CO(2) laser, and the nonlinear coefficient of LiGaTe(2) is determined from comparison with AgGaSe(2). The effective nonlinearity of LiGaTe(2) for this process amounts to 34.