CsZn BO X (X =F , Cl , and FCl): A Series of Beryllium-Free Deep-Ultraviolet Nonlinear-Optical Crystals with Excellent Properties.

Designing deep-ultraviolet (DUV) nonlinear-optical (NLO) crystals is one of the major current research interests, but it faces a great challenge. In order to overcome the problem of crystal growth and the toxicity of BeO raw materials in KBe BO F (KBBF), the only applicable DUV NLO crystal so far, we substitute Be cations with Zn in the KBBF structure and modify the halogen anions, by which three new Zn-containing KBBF-like compounds, CsZn BO X (X =F , Cl , and FCl), have been successfully synthesized. They all exhibit excellent NLO properties, including improved SHG responses (2.8-3.5×KDP) and short UV cut-off edges (<190 nm). In comparison with KBBF, CsZn BO X (X =F , Cl , and FCl) are all chemically benign and have better growth habits, so they are all promising as DUV NLO crystals. Further study on structure-property relationships indicates that the mixing of halogen anions is a feasible strategy to enhance the SHG responses of the KBBF family.