Energy transfer in Er:Eu:Yb co-doped tellurite glasses: Yb as enhancer and quencher

Energy transfer has been studied from Er³⁺ to Eu³⁺ ions on excitation with NIR photons (796 and 980 nm) with and without Yb³⁺ ions. It is found that in one case the presence of Yb³⁺ enhances the fluorescence yield (980 nm excitation) whereas in the other case it quenches (796 nm excitation). Energy transfer from Er³⁺ ion's levels ⁴S_3/2 and ²H_11/2 is verified by decay curve analysis in both the cases. The nature of interaction between the donor (Er) and the acceptor (Eu) ions is found to be dipole-dipole. The energy transfer parameters viz. transfer probability, critical distance etc. have been calculated.