Rare-earth oxychalcogenide Eu2ZnGe2OS6: a phase-matching infrared nonlinear optical material with [GeOS3] units

Abstract

Oxychalcogenides have been highly anticipated as nonlinear optical (NLO) crystals because of their excellent optical properties. Herein, a rare-earth oxychalcogenide Eu₂ZnGe₂OS₆ was successfully designed and synthesized. It crystallizes in the non-centrosymmetric P2₁m space group with highly polarized mixed-anion [GeOS₃] units and exhibits an indirect band gap of 2.22 eV, a moderate second harmonic generation (SHG) response (0.4 × AGS), and phase-matching properties. Additionally, Eu₂ZnGe₂OS₆ exhibits a significant calculated birefringence of 0.173@2090 nm. This research has enriched the rarely studied rare-earth oxychalcogenide system and provided new ideas for the design of promising IR NLO crystals.