Green and red upconversion emission and energy-transfer between Er3+ and Tm3+ ions in tellurite glasses

Upconversion luminescence and their mechanisms of the Er3+ and Tm3+ codoped tellurite glasses were investigated under both the 975 and 800 nm excitation. By Tm3+ codoping, the Er3+ green emission corresponding to the (S-4(3/2),H-2(11/2)) --> I-4(15/2) transitions was quenched, while the red emission corresponding to the F-4(9/2) --> I-4(15/2) transition was selectively sensitized. The red emission has a maximum in the range where the ratio of Er3+- to TM3+-content is about two and its fluorescence intensity becomes 1.5 and 5 times larger at the maximum than in the absence of Tm3+ for 975 and 800 nm excitation, respectively. The results were explained considering the influence of energy transfers between these two active ions. (C) 2004 Elsevier B.V. All rights reserved.