Highly efficient ~3.4 μm emission of Er3+-doped TeO2 based glasses via resonant energy transfer and multi-phonon relaxation processes

To clarify the relation between the concentration and ~3.4 μm emission of Er3+, a series of TeO2 based glasses with Er3+ concentration from 2.0 to 10.0 mol% were prepared by conventional melting-quenching method. The physical and spectroscopic characteristics of Er3+-doped tellurite glasses were systematically investigated. The Judd-Ofelt theory was used to analyze the absorption spectra. The emission intensity of ~2.7 μm and upconversion at 550 and 670 nm were discussed. The intensity increased when the Er3+ concentration increased to 6 mol%, and then drastically decreased with further increasing Er3+ concentration. The trend of the emission properties in NIR with the Er3+ concentration was also discussed. With increasing Er3+ concentration, the emission cross section at ~3.4 μm increased from 1.37 × 10−21 cm2 to 2.53 × 10−21 cm2. The results indicate that the highly doped Er3+ concentration may be an effective route to achieve efficient ~3.4 μm emission in Er3+ doped tellurite glasses.