PbGa4S7: a wide-gap nonlinear optical material

Abstract

By combining the [GaS₄] tetrahedra and the second-order Jahn–Teller distorted cation Pb²⁺, a new wide-gap nonlinear optical material PbGa₄S₇ has been obtained. In the structure, Pb²⁺ is coordinated to a distorted quadrangular pyramid of five S atoms, showing the stereo-chemical activity of the 6s² lone pair electrons. The polar arrangement of the [GaS₄] tetrahedra and the macroscopic arrangement of the [PbS₅] distorted quadrangular pyramids result in a large IR nonlinear optical property for PbGa₄S₇, which is ∼1.2 times that of the benchmark AgGaS₂ at a laser radiation of 2.09 μm. Moreover, PbGa₄S₇ has a large direct band gap of 3.08(2) eV, a desirable property for avoiding two-photon absorption of the conventional 1–2 μm pumping laser sources and improving the laser damage threshold. The DSC analysis indicates that the compound is thermally stable up to 1140 K. The electronic structure was also calculated to explain the optical properties.