Remarkable phase-matchable second-harmonic generation realized by strong polarities of [PbSe3] and [GaSe4] functional motifs in PbGa4Se7

Abstract

Strong second-harmonic generation (SHG) and phase-matchable capability at specific transmittance windows are crucial to the real application of nonlinear optical crystals. Herein, an efficient strategy of introducing Pb2+ with stereochemically active lone-pair electrons into non-phase-match-able Ga2Se3 via enhancing the anisotropy microstructure is first applied to meet phase-matchable SHG intensity requirements, offering a selenide, namely, PbGa4Se7, which is designed and synthesized with a diamond-like anionic framework, where Pb2+ cations reside in a parallel arrangement. As expected, PbGa4Se7 possesses a large SHG coefficient of 3.3 times that of AgGaS2 under the incident laser of 1910 nm. Moreover, PbGa4Se7 displays a high laser-induced damage threshold of 7.0 times that of AgGaS2 at 2090 nm, which originates from the low anisotropy of thermal expansion coefficient (0.36) and suitable optical band gap (2.1 eV). Theoretical calculations demonstrate that the considerable phase-matchable SHG response of PbGa4Se7 can be attributed to the synergies of tetrahedral GaSe4 and pyramid PbSe3 microstructural blocks with additional anisotropy and polarizability.[Figure not available: see fulltext.].