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

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 Ga2Se3viaenhancing 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, PbGa4Se7possesses a large SHG coefficient of 3.3 times that of AgGaS2under the incident laser of 1910 nm. Moreover, PbGa4Se7displays a high laser-induced damage threshold of 7.0 times that of AgGaS2at 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 PbGa4Se7can be attributed to the synergies of tetrahedral GaSe4and pyramid PbSe3microstructural blocks with additional anisotropy and polarizability.