Li4 MgGe2 S7 : The First Alkali and Alkaline-Earth Diamond-Like Infrared Nonlinear Optical Material with Exceptional Large Band Gap.

Abstract

Large band gap and strong nonlinear optical (NLO) effect are two valuable but contradictory parameters, which are difficult to balance in one infrared (IR) NLO material. Herein, the first alkali and alkaline-earth metal diamond-like (DL) IR NLO material Li4 MgGe2 S7 , presenting a honeycomb-like 3D framework constructed by 6-membered LiS4 rings and GeMgS6 zigzag chains, was rationally designed and synthesized. The introduction of rigid alkali metal and alkaline-earth metal LiS4 and MgS4 tetrahedra effectively broadens the band gap of DL compound to 4.12 eV (the largest one in the reported quaternary metal chalcogenides), generating a high laser damage threshold of 7 × AgGaS2 at 1064 nm. Furthermore, Li4 MgGe2 S7 displays a suitable SHG response (0.7 × AgGaS2 ) with a type I phase-matching behavior. The results indicate that Li4 MgGe2 S7 is a promising IR NLO material for the high-power laser application and it provides an insight into the design of new DL compound with outstanding IR NLO performances.