High-Performance IR Nonlinear Optical Material Sr3MnGe2S8 Achieved via Partial-Cation-Substitution-Induced Structural Transformation

Abstract

The development of Mn-based infrared nonlinear optical (IR-NLO) materials that concurrently exhibit a large secondharmonic generation response (SHG > 1.0 AgGaS2) and a wide band gap (Eg > 3.0 eV) remains a formidable challenge. Herein, we demonstrate a partial-cation-substitution strategy to address this issue, successfully transforming centrosymmetric Sr2GeS4 into a novel non-centrosymmetric quaternary sulfide, Sr3MnGe2S8. The compound features a three-dimensional framework constructed from corner-sharing [MnS4] and [GeS4] tetrahedra, with Sr 2+ cations residing in the interstitial spaces. Sr3MnGe2S8 achieves an outstanding balance of key IR-NLO properties: it shows a strong SHG response (2.4 × AgGaS2 at 2050 nm), a high laser-induced damage threshold (13.4 × AgGaS2), and a wide Eg of 3.06 eVranking it among the best-performing Mn-based chalcogenides. Theoretical calculations and structural analysis reveal that the excellent NLO performance originates from the synergistic effects between the two distinct types of functional units.This work provides a valuable paradigm for designing high-performance IR-NLO materials through rational structural transformation, highlighting the power of chemical substitution in overcoming property trade-offs.