A new infrared nonlinear optical material BaZnGeS4 with a wide band gap and large nonlinear optical response

Abstract

Developing high-performance infrared (IR) nonlinear optical (NLO) materials is essential for modern laser technology, but challenging due to the competition of the NLO coefficient and band gap in the structure. Based on the “electronic structure engineering bucket effect” and systematic experimental investigations on the A^IIB^IIC^IVD₄^VI family, three new alkaline earth metal sulfides Mg_0.6Cd_1.4GeS₄, CaCdGeS₄, and BaZnGeS₄ have been developed. The compounds show a structural change from the Pnma (CaCdGeS₄) to the Fdd2 (BaZnGeS₄) space group. Among them, BaZnGeS₄ exhibits a phase-matching NLO response of ∼0.8× AGS, a wide band gap of 3.36 eV, and a high laser-induced damage threshold of ∼5.4× AGS, achieving a good balance between the NLO response and band gap, which makes it an excellent IR NLO material. Theoretical calculations show that the NLO effects of BaZnGeS₄ originated from the [ZnS₄] and [GeS₄] NLO-active motifs. The results indicate that BaZnGeS₄ is a promising anti-laser damage IR NLO material and enriches the chemical diversity of the A^IIB^IIC^IVD₄^VI family.