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

Abstract 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 [B 3 O 6 ] units which manipulate the excellent performances of famous commercial NLO crystal β ‐BaB 2 O 4 ( β ‐BBO) to explore new alternatives of deep‐UV NLO materials. A deep‐UV rare‐earth metal borate fluoride Rb 2 ScB 3 O 6 F 2 (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 ( λ PM =182 nm) is shortened by 23 nm compared with β ‐BBO ( λ PM =205 nm) due to the improvements in the chromatic dispersion and cutoff edge, and an experimental frequency‐doubling effect 1.4×KH 2 PO 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.