Insights into the 1.53 μm Luminescence Enhancement in Er³⁺-Doped Tellurite Glasses via Quantum Emitter and Plasmonic Coupling at Low Temperatures

In the literature, the influence of metallic nanoparticles on the luminescence performance of rare-earth ions in glasses at room temperature is extensively discussed. Nevertheless, the interaction with the localized surface plasmon resonance and quantum emitters, in this case, the rare-earth ions, needs to be covered in in-depth analysis, especially in temperature-dependent spectroscopy. In this research, Er³⁺-doped tellurite glasses with and without embedded gold nanoparticles were fabricated to study the coupling between Er³⁺ ions and the localized surface plasmon at controlled temperature. Here, a large emission enhancement, which involves increments of the FWHM and emission intensities, was obtained for the sample with nanoparticles (TErAu) compared with the simple Er³⁺-doped (TEr) at different temperatures (-180 to 25 °C). The increment of the band area of the TErAu with respect to the TEr sample is about 66% at room temperature. Regarding temperature-dependent spectroscopy, the enhancement was quantified by measuring the relative area increment, I_rel, of the 1.53 µm emission band under 980 nm excitation, i.e., the ratio between the band area at a given temperature T and 25 °C (T < 25 °C). The Irel comparing the bands at -180 and 25 °C of the TEr sample is 348%, whereas for the sample TErAu is 414%. The enhancement is a consequence of the strong coupling between the Er³⁺ and the plasmon, which is attributed to an increment of the localized plasmon mode volume at low temperatures. Such mode volume is analyzed considering the changes in temperature-dependent permittivity, thermal contraction, free-electrons density and computing calculations of the damping parameter. These findings provide new directions toward engineering the Er³⁺ emission performance with the presence of gold nanoparticles.