Li2CdSiS4, a promising IR NLO material with balanced Eg and SHG response originated from the effect of Cd with d10 configuration
Infrared (IR) nonlinear optical (NLO) materials are of great importance in laser technology, which could be applied in many civil and military fields. However, the low laser damage threshold and two-photon absortion, which is caused by the small bandgap, hindered the applications of commercial IR NLO materials. In this work, Li2CdSiS4, with wide bandgap (3.76 eV) and moderate second-harmonic generation (SHG) response (1 ×AgGaS2) was successfully designed and fabricated by high temperature flux method in vacumed and sealed quartz tubes. The compound with wurtz-stannite structure type is constructed by hexagonal close packing tetrahedra and meets the requirements of optimal IR NLO material properties. Theoretical results show that Li2CdSiS4 has an indirect bandgap, and the bandgap is determined by the S 3p and Si 3p orbitals but the massive Cd element, which makes Li2CdSiS4 have wider bandgap than other Cd-obtained chalcogenides. In addition, the SHG response originates mainly from the S2- and Cd2+ of CdS4 tetrahedra while Li and Si make ignorable contributions in the compound. All above indicate that Li2CdSiS4 is a promising NLO material in IR field and Cd is a good choice in designing new IR NLO mateirals.