Energy transfer between Tm3+ and Er3+ ions in a TeO2-based glass pumped at diode laser wavelength

In this paper we investigate the energy transfer processes in Tm3+/Er3+ doped telluride glass pumped at the commercial diode laser pump wavelength ∼800 nm. Tailoring the rare-earths content in the glass matrix, seven main energy transfer channels within the doping range considered were identified. A 6-fold enhancement of the Er3+ visible frequency upconversion fluorescence at ∼660 nm is observed due to the inclusion of Tm3+ ions. This is evidence of the relevant contribution of the route Er1(4I11/2) + Er2(4I13/2) → Er1(4I15/2) + Er2(4F9/2) to the process. Energy migration among pumped 4I9/2 level reducing the efficiency of the upconversion emission rate (3H11/2, 4S3/2, and 4F9/2) is observed for Er3+ above 1.5 wt%. The rate equations regarding the observed energy transfer routes are determined and a qualitative analysis of the observed processes is reported.