Pressure-tuning the nonlinear-optical properties of AgGaS2 crystal: a first-principle study

A specialized genetic algorithm approach in combination with first-principles calculations is employed to predict the stable structures of AgGaS2 crystal at different pressures. The results show that the chalcopyrite structure first transforms to the monoclinic Cc phase, and then to a centrosymmetric structure that the second-harmonic generation (SHG) response of AgGaS2 is disappeared. The effects of external pressures, up to 7 GPa, on the linear and second-order nonlinear optical properties of AgGaS2 are explored systematically. Our work reveals that the resistance to laser-induced damage, the transparency range, and the phase matchability can be improved by the pressure-induced deformation of AgGaS2 crystal. Moreover, the feature of the strong SHG response of AgGaS2 crystal is still preserved in the whole IR region even under pressure up to 7 GPa. (C) 2015 Optical Society of America