Effect of iodine (I2) on structural, thermal and optical properties of Ge-Sb-S chalcohalide host glasses and ones doped with Dy

A serial (100   −   x)Ge 25 Sb 10 S 65 -xI (x   =   0, 5, 10, 15, 20, 25 and 30   wt%) chalcohalide glasses and ones doped with 0.1   wt% Dy 3   + rare-earth ions were synthesized and their structural, thermal and optical properties were systematically studied. It indicates that addition of I 2 into Ge 25 Sb 10 S 65 glass significantly decreases the connectivity of glass network and average bond energy, and modifies the associated properties. The glass transition temperature and refractive index decrease monotonically, and the density increases almost linearly with the increasing of iodine content in glass. The thermal stability is improved, which has a maximum of ΔT max   =   174   °C. While the optical bandgap has a peak value at x   =   10   wt%. The absorption spectra and mid-infrared fluorescence spectra of Dy 3   + rare-earth ions doped glasses were investigated together with the Judd-Ofelt analysis. GeS 2 nano-crystals were found in the sample with x   ≥   15   wt%, which is supposed to induce enhancements of mid-infrared fluorescence at 2.95 and 4.32   μm.