Structural, luminescent and upconversion characteristics of Er³⁺ doped titanium zinc tellurite glass

The TeO₂–TiO₂–ZnO glass was single doped with Er³⁺ and its structural, luminescent, and upconversion properties were analyzed. The amorphous nature of the fabricated glass was confirmed by X-ray diffraction, and the characteristic vibrational modes of the tellurite-titanium-zinc glass network were identified by Raman spectroscopy. The photoluminescent and upconversion properties of Er³⁺ doped glass was analyzed by time decay measurements at different excitation wavelengths. The spectra recorded upon excitations at 808 nm and 975 nm show an intense green upconversion luminescence corresponding to the ²H_11/2, ⁴S_3/2 → ⁴I_15/2 transitions and a very weak red emission associated to the ⁴F_9/2 → ⁴I_15/2 transition. The experimental results suggest that in Er³⁺ doped glass the excited state absorption and/or energy transfer mechanisms are responsible for upconversion luminescence observed upon 808 nm and 975 nm excitations.