Birefringent materials are of great importance in optical communication and the laser industry, as they can modulate the polarization of light. Limited by their transparency range, few birefringent materials, except α-BaB2O4 (α-BBO), can be practically used in the deep ultraviolet (UV) region. However, α-BBO suffers from a phase transition and does not have enough transparency in the deep UV region. By introducing the relatively small alkali metal Na+ cation and the F– anion to keep the favorable structural features of α-BBO, we report a new birefringent crystal Na3Ba2(B3O6)2F (NBBF), which has the desirable optical properties. NBBF not only maintains the large birefringence (Δn = no – ne = 0.2554–0.0750 from 175 nm to 3.35 μm) and extends its UV cutoff edge to 175 nm (14 nm shorter than α-BBO) but also eliminates the phase transition and has the lowest growth temperature (820 °C) among birefringent materials. These results demonstrate that NBBF is an attractive candidate for the next generation of deep UV birefringent materials. 

Cryst. Growth Des.,2014