Hg3AsS4X (X = Cl and Br): two Hg-based chalcogenides as long-wave infrared nonlinear optical crystals with superior comprehensive performances

Long-wave infrared (IR) nonlinear optical (NLO) crystals hold great promise for extensive applications. However, IR NLO crystals with outstanding comprehensive optical and NLO performances are still in great demand. Herein, two Hg-based chalcogenides, Hg3AsS4Cl and Hg3AsS4Br, are synthesized via a chemical vapor transport technique. Attributed to the synergistic combination of [HgS3] groups and structurally aligned [AsS3] groups with lone pair electrons, the two compounds exhibit superior NLO performance, encompassing strong second-harmonic generation (SHG) effects, tremendous birefringence, and a broad transparency range, positioning them as promising long-wave IR NLO materials. Moreover, the luminescent performances of the two compounds are also investigated, revealing interesting ultraviolet (UV) region luminescence emissions, broad emission bands, and large Stokes shifts for potential luminescent applications.