Sr₄Pb_1.5Sb₅O₅Se₈: a new mid-infrared nonlinear optical material with a moderate SHG response

A new mid-infrared nonlinear optical oxyselenide compound, Sr4Pb1.5Sb5O5Se8, was successfully synthesized by traditional solid-state reaction. It crystallizes in the noncentrosymmetric space group Cm (No. 8) of the monoclinic system. The crystal structure is composed of edge-sharing quasi-2D (2)(infinity)[Pb1.5Sb3-Se-8](4-) zigzag layers with Sr2+ ions and anionic (1)(infinity)[SbO2.5](2-) pseudo-chains separating the adjacent layers. The compound has good thermal stability up to approximately 1000 K which is beneficial for nonlinear optical applications. The sharp down signal of the second harmonic generation (SHG) response measured with a 2.09 mu m laser in the reflection mode reveals its nonlinear optical properties. The new compound Sr4Pb1.5Sb5O5Se8 provides some guidance to design new mid-infrared nonlinear optical materials.