Optical Nonlinearity in Cu_2CdSnS_4 and α/β-Cu_2ZnSiS_4: Diamond-like Semiconductors with High Laser-Damage Thresholds

摘要

Cu_2CdSnS_4 and α/β-Cu_2ZnSiS_4 meet several criteria for promising nonlinear optical materials for use in the infrared (IR) region. Both are air-stable, crystallize in noncentrosymmetric space groups, and possess high thermal stabilities. Cu_2CdSnS_4 and α/β- Cu_2ZnSiS_4 display wide ranges of optical transparency, 1.4?25 and 0.7?25 μm, respectively, and have relatively large second-order nonlinearity as well as phase matchability for wide regions in the IR. The laser-damage threshold (LDT) for Cu_2CdSnS_4 is 0.2 GW/cm~2, whereas α/β-Cu_2ZnSiS_4 has a LDT of 2.0 GW/cm~2 for picosecond near-IR excitation. Both compounds also exhibit efficient third-order nonlinearity. Electronic structure calculations provide insight into the variation in properties.