Rational design of a promising oxychalcogenide infrared nonlinear optical crystal

Oxychalcogenides with the performance-advantages of both chalcogenides and oxides are emerging materials class for infrared (IR) nonlinear optical (NLO) crystals that can expand the wavelength of solid-state lasers to IR regions and are of importance in industrial and civil applications. But rationally designing a high-performance oxychalcogenide NLO crystal remains a great challenge. Herein, we chose the melilite-type Sr₂ZnSi₂O₇ as the structure template. Through part isovalent substitution of S^2- for O^2- anions, the first hetero-anionic thiostannate Sr₂ZnSn₂OS₆ with wide IR transmission has been synthesized. More importantly, compared to the maternal oxide, Sr₂ZnSi₂O₇, the second harmonic generation (SHG) response of Sr₂ZnSn₂OS₆ is enhanced by two orders of magnitude. In addition, Sr₂ZnSn₂OS₆ can exhibit a large band-gap and high laser damage threshold. These advantages make Sr₂ZnSn₂OS₆ a promising IR NLO crystal. Our research will provide insights into the rational design of new IR NLO crystals.