Design of deep-ultraviolet nonlinear optical materials based on fundamental building blocks with excellent microscopic properties

Nonlinear optical (NLO) materials are designed based on fundamental building blocks (FBBs) with excellent microscopic properties, which is conducive to obtaining high-performance materials. Here, the [B3O7] group similar to the [B3O6F] group is considered to have excellent microscopic properties. According to this, a structure with FBBs of [B3O6F]: Li2B3O5F is designed. Li2B3O5F is capable of achieving deep-ultraviolet (deep-UV) transparency with short absorption edges below 200 nm (E-g = 6.37 eV). The birefringence is 0.10@1064 nm, which brings a short phase-matching (PM) wavelength of about 195 nm. Finally, the relationship between structure and performance of Li2B3O5F is clarified by first-principles calculation.