A bifunctional primitive strategy induces enhancements of large second harmonic generation and wide UV transmittance in rare-earth borates containing [B₅O₁₀] groups

Abstract

Strong second-harmonic generation (SHG) and short ultraviolet (UV) cutoff edge are two crucial yet often conflicting parameters that must be finely tuned in the exploration of nonlinear optical (NLO) materials....

A Rare-Earth-Based Borate Optical Crystal with Enlarged Dihedral Angles of Distinct [BO3] Groups Exhibiting a Wide UV Transparent Range

“…Recent developments have yielded a series of novel NLO and birefringent crystals featuring coplanar π-conjugated functional building units, such as CaZn 2 (BO 3 ) 2 , Ba 4 B 14 O 25 , Ca 3 (BO 3 ) 2 , Ba 2 Mg­(BO 3 ) 2 , and NaMgBO 3 with [BO 3 ] planar triangles. − In the pursuit of advanced UV optical crystal materials, rare-earth ions, particularly Sc 3+ , Y 3+ , La 3+ , Gd 3+ , and Lu 3+ , which exhibit no d–d or f–f electronic transitions, are introduced into borate systems with planar structural motifs. The introduction of these rare-earth cations not only contributes to good transparency in the UV region but also enhances the microscopic polarity and structural anisotropy through their inherent distortive polyhedra. − As a result, a variety of rare-earth borates, such as LaBO 3 , Li 2 MY 4 B 5 O 15 (M = Rb, Cs), K 5 Mg 2 La 3 (BO 3 ) 6 , KNa 2 La 2 (BO 3 ) 3 , and K 7 BaRE 2 (B 5 O 10 ) 3 (RE = Sc, Y, Lu, Gd), − have been identified as potential candidates for UV birefringent or NLO crystals. Accordingly, the combination of rare-earth ions with borates containing planar structural units has proven to be an effective strategy in the exploration of UV optical crystals.…”