AgIn5Se8: a defect diamond-like non-linear optical selenide

A defect diamond-like mid-IR NLO material, AgIn5Se8, is synthesized and its NLO performance has been systematically studied for the first time. This compound exhibits a large SHG response about 0.7 times that of commercial AgGaS2. First-principles calculations reveal that the non-bonding electrons near the Se atoms make the dominant contribution to the SHG response. Furthermore, in order to improve the optical transparency range on a short-wave edge in AgIn5Se8, material design is carried out to enlarge the band gap while keeping the strong SHG response.