Designing rare earth borates as UV nonlinear optical crystals exhibiting strong second-harmonic generation responses

Two new rare earth borate NLO crystals, K₆NaSrY₂B₁₅O₃₀ and Rb₇BaLu₂B₁₅O₃₀, were successfully designed and synthesized, which feature NLO-active [B₅O₁₀] groups and [Y/LuO₆] polyhedra. They exhibit notably short UV absorption cutoff edges below 200 nm, wide band gaps exceeding 6.2 eV, and strong second-harmonic generation intensities that are comparable to KDP. These findings suggest that both compounds are promising NLO candidates in the short-wave UV window.