Stable Lead Succinate-Iodides with Strong Second-Harmonic Generation Response and Large Birefringence

Abstract

Nonlinear optical (NLO) crystals can expand the wavelength of coherent light by frequency conversion, and thus have significant applications in modern lasers, semiconductor manufacturing and lithography. However, the targeted synthesis of high-performance NLO crystals remains an ongoing challenge. Herein, two stable strong NLO crystals, (A2I)[PbI(OOC(CH2)2COO)] (A = Rb, K), have been rationally obtained through a convenient mixed solvothermal method. The highly distorted [PbI2O4] polyhedra which owns large hyperpolarizability and polarizability anisotropy adopt an oriented arrangement that enables favourable superposition of their microscopic second-order susceptibilities. Remarkably, (A2I)[PbI(OOC(CH2)2COO)] (A = Rb, K) not only exhibit strong phase-matching SHG response (7.3 and 5.8 × KDP) and large birefringence (0.205 and 0.245 @ 1064 nm), but also present high thermal stability up to 250 oC in air and good crystal growth habit. Based on theoretical calculations and structural analysis, their strong SHG response are predominantly originated from the distorted [PbI2O4] polyhedron. This study provides an efficient approach for the future discovery of new high-performance NLO crystals.