Sr4Pb1.5Sb5O5Se8: a new mid-infrared nonlinear optical material with a moderate SHG response

Abstract

A new mid-infrared nonlinear optical oxyselenide compound, Sr₄Pb_1.5Sb₅O₅Se₈, 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_∞[Pb_1.5Sb₃Se₈]⁴⁻ zigzag layers with Sr²⁺ ions and anionic ¹_∞[SbO_2.5]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 Sr₄Pb_1.5Sb₅O₅Se₈ provides some guidance to design new mid-infrared nonlinear optical materials.