New Compressed Chalcopyrite-like Li2BaMIVQ4 (MIV = Ge, Sn; Q = S, Se): Promising Infrared Nonlinear Optical Materials.

Chalcopyrite-type AgGaQ2 (Q = S, Se) and ZnGeP2 are the main commercial infrared nonlinear optical (IR NLO) crystals. Unfortunately, performance defects including low laser damage threshold (LDT), harmful two-photon absorption (TPA), or small birefringence limit their application. With this background, four new compressed chalcopyrite-like IR NLO materials Li2BaMIVQ4 (MIV = Ge, Sn; Q = S, Se) were successfully synthesized with the typical AgGaQ2 as templates. Remarkably, Li2BaGeS4 and Li2BaSnS4 not only maintain the good NLO responses (0.5 and 0.7 × AgGaS2) but also overcome low LDTs and TPA of commercial chalcopyrites, demonstrating that they satisfy critical demands as promising IR NLO candidates. All of them exhibit phase-matching abilities. Furthermore, the discovery of chalcopyrite-like compounds also provides a feasible design strategy to explore new promising IR NLO materials.