1D Bi Ribbon/[PO4] Synergy-Driven Bismuth Phosphates for Ultraviolet Nonlinear Optical Crystals with Large SHG and Birefringence

By leveraging second-harmonic generation (SHG) capabilities, ultraviolet (UV) nonlinear optical (NLO) crystals can efficiently produce UV coherent light and are essential components for advancing UV solid-state laser systems. Herein, two new bismuth phosphates, Rb1.32Bi3.56P2O11 (I) and K1.08Bi3.64P2O11 (II), were synthesized via a high-temperature melt method. Of them, Rb1.32Bi3.56P2O11 exhibits a significant phase-matching SHG response (2.8 × KDP) and large birefringence (0.062 @ 532 nm, 0.053@1064 nm), along with an expanded UV transmission window. Moreover, theoretical analyses revealed that the optimized optical polarizability of Rb1.32Bi3.56P2O11 primarily arises from the cooperative effects of the one-dimensional (1D) polycationic Bi(2)Bi(2)×Bi(1)Bi(1)×Bi(1)Bi(1)×Bi(2)Bi(2) ribbons and [PO4] tetrahedron. We believe the work will provide a valuable strategy to design UV NLO materials with good performances.