A new phase-matchable nonlinear optical silicate: Rb2ZnSi3O8

Abstract

Nonlinear optical (NLO) crystals are key materials for generation of coherent light in solid state lasers. A new NLO material Rb₂ZnSi₃O₈ is synthesized by the traditional solid-state reaction technique and its crystals are obtained by spontaneous crystallization using an Rb₂O–B₂O₃ flux. It crystallizes in an asymmetric space group of C2 (No. 5) and features a three-dimensional framework composed of SiO₄ and ZnO₄ tetrahedral groups. Remarkably, it exhibits a phase-matchable powder second harmonic generation approximately 2.5 times that of α-SiO₂, which is well known to be non-phase-matchable. The first-principle calculations reveal that the Si–O and Zn–O tetrahedra determine the optical properties in the Rb₂ZnSi₃O₈ crystal and may be the origin of the phase matching behavior in Rb₂ZnSi₃O₈. The UV-visual-near-infrared diffuse reflectance spectrum shows that Rb₂ZnSi₃O₈ has a wide transparency window down to the deep-UV spectral region. In addition, Rb₂ZnSi₃O₈ is non-hygroscopic. These results suggest that Rb₂ZnSi₃O₈ is a potential deep-UV NLO crystal.