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 (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×KH₂PO₄ (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.