Designing A New Infrared Nonlinear Optical Material, beta-BaGa2Se4 Inspired by the Phase Transition of the BaB2O4 (BBO) Crystal

Infrared nonlinear optical (IR NLO) crystals play a significant role in the development of IR laser technology. But rationally designing a new IR NLO crystal remains a huge challenge because of the unpredictability of inorganic structures. Herein, inspired by phase transformation of the famous BaB2O4 (BBO) crystal, a temperature-induced centrosymmetric (CS) to noncentrosymmetric (NCS) transformation approach is employed in CS BaGa2Se4 to uncover a new NCS ternary chalcogenide, beta-BaGa2Se4 which can exhibit the well-balanced NLO properties, including moderate phase-matching SHG response (approximate to 0.6xAgGaS(2)), high LDT (10xAgGaS(2)), and large birefringence (Delta n=0.18 in the visible region). Therefore, beta-BaGa2Se4 will be a promising IR NLO crystal. The analysis for the structure-property relationship shows that the excellent NLO properties of beta-BaGa2Se4 mainly originate from edge-sharing GaSe4 tetrahedral chains, which are different from B3O6 groups in beta-BBO and respect a new direction for the design of IR NLO crystals. So, we believe that the current research provides not only a new IR NLO crystal but also some insights for the design of new IR NLO crystals.