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

Abstract

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 BaB 2 O 4 (BBO) crystal, a temperature‐induced centrosymmetric (CS) to noncentrosymmetric (NCS) transformation approach is employed in CS BaGa 2 Se 4 to uncover a new NCS ternary chalcogenide, β‐BaGa 2 Se 4 which can exhibit the well‐balanced NLO properties, including moderate phase‐matching SHG response (≈0.6×AgGaS 2 ), high LDT (10×AgGaS 2 ), and large birefringence (Δ n =0.18 in the visible region). Therefore, β‐BaGa 2 Se 4 will be a promising IR NLO crystal. The analysis for the structure‐property relationship shows that the excellent NLO properties of β‐BaGa 2 Se 4 mainly originate from edge‐sharing GaSe 4 tetrahedral chains, which are different from B 3 O 6 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.