Deep-Ultraviolet Nonlinear-Optical Material K3Sr3Li2Al4B6O20F: Addressing the Structural Instability Problem in KBe2BO3F2.

A beryllium-free deep-ultraviolet (DUV) nonlinear-optical (NLO) material, K3Sr3Al4Li2B6O20F, has been synthesized and characterized. Unlike KBe2BO3F2 (KBBF), the reported NLO material does not require the use of toxic BeO in the synthesis, and through the judicious selection of cations, strong interlayer interactions are observed that facilitate the crystal growth. K3Sr3Al4Li2B6O20F exhibits second-harmonic generation (SHG) at both 1064 and 532 nm with efficiencies of 1.7KH2PO4 and 0.3β-BaB2O4 and has an absorption edge of 190 nm. Because of the strong interlayer interactions, we were able to grow well-faceted large crystals, 8 × 8 × 5 mm3, through a top-seeded-solution-growth technique. With these crystals, we determined a birefringence of 0.0574 at 1064 nm and a type I phase-matching SHG limit of 224 nm.