Nonlinear optical properties of organic-inorganic hybrid perovskite

Nonlinear optical properties of materials play important roles in lasers, frequency conversion, electro-optic modulators, etc. Here we explore the nonlinear optical properties of hybrid CH₃NH₃MX₃ perovskites (M= Ge, Sn, Pb; X=Cl, Br, I), which are widely studied in photovoltaic areas. Using first-principles approaches, different phases of hybrid perovskites have been studied, and we find considerably large second harmonic generation (SHG) in some of them. Interestingly, large non-diagonal SHG tensors appear in certain structures, which are fairly useful for real-world applications, such as tuning the directions of lasers. All calculations are implemented in our self-developed package aiming for large-scale parallel calculations of nonlinear optical properties.