Four UV Transparent Linear and Nonlinear Optical Materials Explored from Pure Selenite Compounds

Abstract UV nonlinear optical materials require the simultaneous achievement of a large second harmonic generation (SHG) coefficient (≥1 × KH₂PO₄ (KDP), d_ij > 0.39 pmV⁻¹), wide bandgap (λ < 300 nm, E_g > 4.2 eV), and moderate birefringence (0.05‐0.10@1064 nm) in a single structure. Therefore, designing UV nonlinear optical materials with excellent comprehensive performance is a challenging task. Herein, four UV transparent selenite materials are successfully obtained, namely, Al₂(SeO₃)₃(H₂O)₃ (1), Ga₂(SeO₃)₃(H₂O)₃ (2), NaGa₃(HSeO₃)₆(SeO₃)₂ (3), and Cd₅Ga₄(HSeO₃)₂(SeO₃)₁₀ (4), through rational design and screening in the pure selenite system. Al₂(SeO₃)₃(H₂O)₃ (1) and Ga₂(SeO₃)₃(H₂O)₃ (2) are UV nonlinear optical materials with balanced properties, exhibiting moderate SHG responses (1.2 and 1.1 × KDP), appropriate birefringence (0.084 and 0.076@1064 nm), and wide bandgaps (5.5 and 5.3 eV). Such bandgaps are the largest in the reported pure selenite nonlinear optical (NLO) materials. This work further demonstrates that pure selenite is a good candidate for UV NLO materials.