Near-infrared and upconversion luminescence of Tm3+ and Tm3+/Yb3+-doped oxyfluorosilicate glasses

Oxyfluorosilicate glasses-doped with different concentrations of Tm3+ and Tm3+/Yb3+ ions have been synthesized and characterized their absorption, photoluminescence, luminescence decay and upconversion properties. The Judd-Ofelt intensity parameters have been obtained from the absorption spectrum of Tm3+ single-doped glass and are in turn used to calculate radiative properties such as transition probabilities, branching ratios and lifetimes for the fluorescent levels of Tm3+ ions. Visible and near-infrared emission spectra of Tm3+ and Tm3+/Yb3+-doped glasses have been measured under 473 nm laser excitation. The quenching of emission intensities at higher concentrations of Tm3+ ions has been found to be due to cross-relaxation mechanisms. The Tm3+/Yb3+ co-doped glasses show upconverted emissions under 975 nm laser excitation. The mechanism of upconversion has been explained based on the pump power dependence of upconversion luminescence. The results reveal that the co-doped glasses are promising for optical fiber amplifiers operating at the relatively low-loss wavelength regions.