Intense frequency upconversion emission of Er3+/Yb3+-codoped natrium-barium-strontium-lead-bismuth glasses

Er3+/Yb3+-codoped natrium-barium-strontium-lead-bismuth glasses for developing potential upconversion lasers have been fabricated and characterized. Based on the results of energy transfer efficiency and upconversion fluorescence spectra, the optimal Yb3+-Er3+ concentration ratio is found to be 5:1. Intense green and red emissions centered at 525, 546, and 657 nm, corresponding to the transitions H-2(11/2) --> I-4(15/2), S-3/2 --> I-4(15/2) and F-2(9/2) --> I-4(15/2), respectively, were observed at room temperature. The quadratic dependence of the 525, 546, and 657 urn emissions on excitation power indicates that a two-photon absorption process occurs under 975 nm excitation. The long-lived I-4(11/2) level is supposed to serve as the intermediate state responsible for the upconversion processes. (C) 2004 Elsevier Ltd. All rights reserved.