Effect of concentration on down- and up-conversion luminescence in Er³⁺doped lithium-zinc-tellurite glass

The effect of Er₂O₃ concentration on the structural, physical, and spectroscopical properties of (70-x)TeO₂-20ZnO-10Li₂O-xEr₂O₃ glasses (x = 0.1–4 mol %) was studied by X-ray diffraction (XRD), Energy dispersive spectroscopy (EDS), Fourier transformed infrared spectroscopy (FT-IR), density measurements, optical absorption, photoluminescence, and time-resolved spectroscopic techniques. All glasses are amorphous, as observed by XRD. FT-IR showed changes in the non-bonding oxygens band, and EDS detected aluminum from crucible leaching, which influenced the physical properties. According to optical absorption spectra, the doped glasses are more UV transparent than the glass matrix. Photoluminescence was characterized first under a UV excitation wavelength, determining the time decay and Er³⁺→Er³⁺ energy transfer mechanisms by monitoring the ²H_11/2→⁴I_15/2 and ⁴S_3/2→⁴I_15/2 transitions. The up-conversion process was monitored using two CW lasers with wavelengths of 808 and 975 nm, varying the power in a wide range, and it was determined that the two-photon process dominates the anti-stokes emission mechanism.