Chalcogenide glasses with embedded ZnS nanocrystals: Potential mid-infrared laser host for divalent transition metal ions

Chalcogenide glasses (ChGs) containing II-VI chalcogenide (ChG) nanocrystals such as ZnS/Se have recently been intensively studied as promising mid-infrared nonlinear optics and laser materials, yet preparation of pure-phase II-VI nanocrystals embedded in ChGs via controlled crystallization is still very challenging. In this study, a new system of ChGs and glass ceramics (GCs), viz., (100−x)As₂S₃–xZnSe (x = 0 ~ 30 mol%), is synthesized, and its physical and optical properties including density, molar volume, microhardness, glass transition temperature, glass network structure, transmission, and refractive index are comprehensively characterized. Significantly, it is initially demonstrated that pure ZnS nanocrystals can be precipitated in GCs simply by a thermal treatment process. The composition and thermal treatment temperature dependencies of crystallization are studied using X-ray diffraction spectroscopy, and the morphology of the nanocrystals by high-resolution transmission electron microscope. The ChG GCs with embedded ZnS nanocrystals retaining good transparency can be a potential host laser material for divalent transition metals (e.g., Cr²⁺/Fe²⁺, etc.), and thus used for ultrabroadband tunable continuous or ultra-short-pulsed mid-infrared fiber lasers.