Na<sub>6</sub>MQ<sub>4</sub> (M=Zn, Cd; Q=S, Se): Promising New Ternary Infrared Nonlinear Optical Materials
Yi Huang, Le Gao, Haohai Yu, Zhihua Yang, Junjie Li, Shilie Pan
Abstract
Abstract Four sodium‐based ternary IR nonlinear optical (NLO) materials, Na 6 MQ 4 (M=Zn, Cd; Q=S, Se), were prepared through a high‐temperature flux method. The crystal structure of the compounds is built up of isolated [MQ 4 ] tetrahedra and a 3D framework formed by the NaQ n ( n =4, 5) units. The two selenides, Na 6 MSe 4 (M=Zn, Cd), as promising IR NLO materials, show moderate second‐harmonic generation (SHG) responses (0.9 and 0.5×AgGaS 2 ) with good phase‐matching behavior, as well as high laser damage thresholds (2 and 1.9×AgGaS 2 ). The two sulfides, Na 6 MS 4 (M=Zn, Cd), exhibit higher laser damage thresholds (13 and 4×AgGaS 2 ), but smaller SHG responses (0.3 and 0.2×AgGaS 2 ). Theoretical calculations and statistical analyses indicate that the SHG effect and band gap in the compounds originate mainly from the distorted NaQ 4 NLO‐active units with a short Na−S bond length, which provides a new insight into the design of novel IR NLO materials.