Mechanisms and Concentration Dependence of Upconversion Fluorescence in Er3+ and Tm3+ Codoped Tellurite Glasses
Mechanisms and Concentration Dependence of Upconversion Fluorescence in Er^3＋ and Tm^3＋ Codoped Tellurite Glasses

We investigate the upconversion luminescence of Er3^ and Tm^3 codoped tellurite glasses under both the 975 and 80Ohm excitations. By Tm^3 codoping, the Er^3 green emission corresponding to the (^4S3/2, 2H11/2) → 4I15/2 transitions was quenched, while the red emission corresponding to the ^4F9/2 → ^4I15/2 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 those in the absence of Tm^3 for 975 and 800 nm excitations, respectively. The results were explained considering the influence of energy transfers between these two active ions.