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

Abstract 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, β‐BaGa2Se4 which can exhibit the well‐balanced NLO properties, including moderate phase‐matching SHG response (≈0.6×AgGaS2), high LDT (10×AgGaS2), and large birefringence (Δn=0.18 in the visible region). Therefore, β‐BaGa2Se4 will be a promising IR NLO crystal. The analysis for the structure‐property relationship shows that the excellent NLO properties of β‐BaGa2Se4 mainly originate from edge‐sharing GaSe4 tetrahedral chains, which are different from B3O6 groups in β‐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.