Exploiting Deep‐Ultraviolet Nonlinear Optical Material Rb2ScB3O6F2 Originated from Congruously Oriented [B3O6] Groups

The exploration and research for deep-ultraviolet (UV) nonlinear optical (NLO) crystals are of great significance for all-solid-state lasers. This work is based on the excellent structural [B3O6] units which manipulate the excellent performances of famous commercial NLO crystal β-BaB2O4 (β-BBO) to explore new alternatives of deep-UV NLO materials. A deep-UV rare-earth metal borate fluoride Rb2ScB3O6F2 (RSBF) is successfully designed by combining the heterovalent ions substitution strategy, and fluorination strategy. Expectedly, RSBF exhibits an extremely short cutoff edge below 175 nm (189 nm for β-BBO), and a moderate birefringence of 0.088 at 1064 nm. The shortest phase-matching (PM) wavelength of RSBF (λPM = 182 nm) is shortened by 23 nm compared with β-BBO (λPM = 205 nm) due to the improvements in the chromatic dispersion and cutoff edge, and an experimental frequency-doubling effect 1.4×KDP further suggests that RSBF can output a deep-UV harmonic laser. This work provides new sights from the original influencing factors for the rational and purposeful design of deep-UV NLO materials.