(Na_0.74 Ag_1.26 )BaSnS₄ : A New AgGaS₂ -Type Nonlinear Optical Sulfide with a Wide Band Gap and High Laser Induced...

The development of high-power solid-state lasers is in urgent need of infrared (IR) nonlinear optical (NLO) materials with wide band gaps and high laser-induced damage thresholds (LIDTs). Herein, a new compressed chalcopyrite-like IR NLO crystal (Na_0.74 Ag_1.26 )BaSnS₄ was successfully synthesized using a facile high-temperature solid-state method. Its structure can be considered as a variant of chalcopyrite AgGaS₂ (AGS)-type ones. It features a three-dimensional framework constructed by corner-sharing {[(Na/Ag)S₄ ]^7- }_∞ layers and isolated SnS₄ tetrahedra with negative cavities occupied by counter ion Ba²⁺ . (Na_0.74 Ag_1.26 )BaSnS₄ exhibits phase-matchable moderate SHG response (0.31 × AGS), wide band gap (3.70 eV), and high LIDT (6.44 × AGS). Theoretical calculations reveal that the NLO response of (Na_0.74 Ag_1.26 )BaSnS₄ is mainly originated from the synergetic effects of AgS₄ and SnS₄ tetrahedra, and the inclusion of alkaline and alkaline earth metals is responsible for the wide band gap and high LIDT. Moreover, the discovery of this chalcopyrite-like compound will provide a feasible design strategy for the exploration of new promising IR NLO materials.