La3Ga3Ge2S3O10: An Ultraviolet Nonlinear Optical Oxysulfide Designed by Anion-Directed Band Gap Engineering

Chalcogenide-containing compounds have been widely studied as infrared nonlinear optical (NLO) materials. However, they have never been applied in the ultraviolet (UV) region owing to the high energy levels of chalcogen anions, leading to band gap narrowing. We report the synthesis of a new UV NLO oxysulfide La3Ga3Ge2S3O10 with an exceptionally wide band gap of 4.70 eV due to from the unique anion-ordered frameworks comprising 1D (1)(infinity)[(Ga3/5Ge2/5)(3)S3O3] triangular tubes and 0D (Ga3/5Ge2/5)(2)O-7 dimers of corner-sharing (Ga/Ge)S2O2 and (Ga/Ge)O-4 tetrahedra, respectively. Second harmonic generation (SHG) measurements revealed that La3Ga3Ge2S3O10 was phase matchable with twice the SHG response of KH2PO4. The results of theoretical calculations suggest that the strong SHG response is mainly attributable to the S-3p and O-2p orbitals in the occupied states. The anion-directed band-gap engineering may give insights into the application of NLO oxychalcogenides in the UV regions.

Automated summary

Chalcogenide-containing compounds have been widely studied for infrared nonlinear optical materials, but a new UV NLO oxysulfide La3Ga3Ge2S3O10 with an exceptionally wide band gap of 4.70 eV was synthesized and found to exhibit strong second harmonic generation response, potentially opening up new possibilities for NLO oxychalcogenides in the UV region.