A new rare-earth borate birefringent crystal with quasi-two-dimensional [BO3] layers

Abstract

Owing to the vital role of birefringent materials in various advanced optical systems, it is very important to find and design structures with a large birefringence. Thus, the LaBO₃ crystal was investigated. It exhibits a structural characteristic of quasi-two-dimensional [BO₃] layers formed by separate [BO₃] groups, which leads to a moderate birefringence (0.093@546 nm). Besides, the LaBO₃ crystal presents a short ultraviolet absorption cutoff of 237 nm corresponding to the band gap of 5.23 eV (the calculated value of 4.81 eV). Remarkably, the LaBO₃ crystal possesses a large transparency window with a transmittance of more than 60% in the region of 300–2000 nm. Therefore, this study points out a promising birefringent crystal and further confirms a favorable structure of the quasi-two-dimensional [BO₃] layer to a large birefringence, which could facilitate the design of new ultraviolet and deep-ultraviolet birefringent crystals.