Up-conversion fluorescence and low-temperature emission in Er3+-doped GeGaS–CsBr glasses

Optical properties of Er-doped chalcohalide GeGaS–CsBr glasses have been investigated as a function of Er and Ga concentrations. Nominal compositions of (Ge0.25Ga.0.10S0.65)0.9(CsBr)0.1 and (Ge0.23Ga.0.12S0.65)0.9(CsBr)0.1 glassy hosts have been chosen for this study. The effects of Er content and host composition on 1.5 μm emission of Er3+ ions, measured at low-temperature of 20 K under excitation by 514.5 nm, have been specified. Besides, the up-conversion fluorescence of Er3+ ions pumped at 795 nm is reported. Two intense emission bands in the green and one weak emission band in the red regions around 530, 554 and 644 nm have been observed, and were attributed to 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, and 4F9/2 → 4I15/2 transitions of Er3+ ions, respectively. The simplified energy-level diagram of Er3+ ion has been used to identify the observed up-conversion fluorescence bands in visible region.