Novel insights on energy transfer processes in [Ce⁴⁺/Ce³⁺]-Er³⁺-doped tellurite glass

Previous works have been already reported on multiphonon-assisted non-resonant energy transfer in Ce³⁺-Er³⁺-doped tellurite glasses. However, it is not clear the mechanism of the radiative emission of Er³⁺ centered at 1530 nm. In this paper, we reported a better understanding of the mechanism of interactions between those two rare-earth ions via a systematic study. For that, we will explore the energy transitions between Ce⁴⁺/Ce³⁺ and Er³⁺ ions in a tungsten-tellurite glass to both emission (in the near infrared) and upconversion (in the visible) spectrum. Here, Ce⁴⁺ and Ce³⁺ were obtained in an Er³⁺-doped tellurite glasses via the addition of different concentrations of CeO₂ as part of the composition of the samples. Emission spectrum, under a 980 nm excitation, giving rise to a series of interactions between Ce³⁺↔Er³⁺ resulting in: (i) a subtle increase of the Er³⁺ emission intensity in the near-infrared region for 0.1 mol% of CeO₂, and then a decrease in the emission for higher CeO₂ concentration in both cases without any significant increase in the bandwidth, and (ii) a decrease of the visible upconversion emission intensity with the addition of CeO₂. Such interactions are achieved via a coupling yielding and energy transfer from both rare-earth ions.