High‐Performance Sulfate Optical Materials Exhibiting Giant Second Harmonic Generation and Large Birefringence

Abstract

AbstractDiscovering novel sulfate optical materials with strong second‐harmonic generation (SHG) and large birefringence is confronted by a great challenge attributed to the intrinsically weak polarizability and optical anisotropy of tetrahedral SO4 groups. Herein, two superior‐performing sulfate optical materials, namely, noncentrosymmetric Hg3O2SO4 and centrosymmetric CsHgClSO4 ⋅ H2O, have been successfully synthesized through the introduction of a highly polarizable d10 metal cation, Hg2+. The unique component layers in the reported compounds, [Hg3O2SO4]∞ layers in Hg3O2SO4 and [HgClSO4(H2O)] layers in CsHgClSO4 ⋅ H2O, induce enlarged birefringence in each sulfate. Remarkably, Hg3O2SO4 exhibits a very large SHG response (14 times that of KH2PO4), which is the strongest efficiency among all the reported nonlinear optical sulfates. Detailed theoretical calculations confirm that the employment of highly polarizable Hg2+ is an effective strategy to design superior optical materials with large birefringence and strong SHG response.