Optical transitions and upconversion luminescence of Er3+/Yb3+ codoped lead-zinc-tellurite oxide glass

Er3+/Yb3+ codoped TeO2-ZnO-PbO (TZP) glass suitable for developing optical fiber laser and amplifier has been fabricated and characterized. The transition probabilities, excited state lifetimes, and the branching ratios have been predicted for Er3+ based on the Judd-Ofelt theory. The broad 1.5 mu m fluorescence was observed under 970 nm excitation, and its full width at half maximum (FWHM) is 72 run. The emission cross-section is calculated using the McCumber theory, and the peak emission cross-section is 8.77 x 10(-21) cm(2) at 1532 nm. This value is much larger than those of the silicate and phosphate glasses. Under 970 nm excitation, efficient 526, 547, and 658 nm upconversion emissions are due to two-photon absorption processes. The possible upconversion mechanisms are discussed based on the energy matching conditions and the quadratic dependence on excitation power. And the standardized upconversion efficiency for green upconversion light is 8.8 x 10(-4), and this value is comparable to those reported in bismuth and fluoride glasses. (c) 2007 Elsevier B.V. All rights reserved.