Sr4Pb1.5Sb5O5Se8: 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∞[Pb1.5Sb3Se8]4− zigzag layers with Sr2+ ions and anionic 1∞[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 μm 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.