Second harmonic generation response of the cubic chalcogenides Ba_(6−x)Sr_x[Ag_(4−y)Sn_(y/4)](SnS₄)₄

We synthesized the barium/strontium solid solution sequence Ba_6−xSr_x[Ag_(4−y)Sn_(y/4)](SnS₄)₄ for nonlinear optical (NLO) applications in the infrared (IR) via a flux synthesis route. All title compounds are isotypic, crystallizing in the cubic space group I 4̅3d and are composed of a three-dimensional (3D) anionic framework of alternating corner-sharing SnS₄ and AgS₄ tetrahedra charge balanced by Ba and Sr. The shrinkage of Ba/Sr–S bond lengths causes the tetrahedra in the anionic framework to become more distorted, which results in a tunable band gap from 1.58 to 1.38 eV with increasing x values. The performance of the barium limit (x=0) is also superior to that of Sr (x=6), but surprisingly second harmonic generation (SHG) of the solid solution remains strong and is insensitive to the value of x over the range 0–3.8. Results show that the non-type-I phase-matched SHG produced by these cubic chalcogenides display intensities higher than the benchmark AgGaSe₂ from 600 to 1000 nm.