Heterovalent cations substitution to design asymmetric chalcogenides with promising nonlinear optical performances

Metal chalcogenides are charming candidates for nonlinear optical (NLO) materials due to their multiple functional structural units and large polarizability. Here, isostructural Sn-based chalcogenides BaZnSnQ(4) (Q = S, Se) were successfully synthesized based on the idea of heterovalent cations co-substitution of the Ga site in the parent BaGa2Se4. They crystallize in an orthorhombic system with polar space group Fdd2. Their structures are built by the NLO functional motifs ZnQ(4) and SnQ(4) tetrahedra. BaZnSnS4 (1) and BaZnSnSe4 (2) exhibit good SHG effects (0.6 and 1.0 times than that of AgGaS2) and also show type-I phase-matchable behaviors. In addition, their laser-induced damage thresholds are about 9.8 and 5.7 times higher than that of AgGaS2, respectively. BaZnSnS4 possesses a larger bandgap (3.25 eV) among the quaternary chalcogenide AM(II)M(IV)Q(4) (A = Sr, Ba; M-II = Zn, Cd, Hg; M-IV = Si, Ge, Sn; Q = S, Se) system. On the basis of theoretical calculation result, the source of SHG responses can be assigned to the synergetic effect of large distorted tetrahedral units. The achievement of this work provides a route to obtain new infrared NLO materials.

Automated summary

Metal chalcogenides, particularly the isostructural Sn-based chalcogenides BaZnSnQ(4) (Q = S, Se), have shown good SHG effects and higher laser-induced damage thresholds compared to AgGaS2. Their structures are built by NLO functional motifs ZnQ(4) and SnQ(4) tetrahedra. The synergetic effect of large distorted tetrahedral units is believed to be the source of the SHG responses in these materials, providing a route to obtain new infrared NLO materials.