Green and red upconversion emission and energy-transfer between Er 3+ and Tm 3+ ions in tellurite glasses

Abstract

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