A new phase-matchable nonlinear optical silicate: Rb2ZnSi3O8

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.