Investigation of the TeO 2 /GeO 2 Ratio on the Spectroscopic Properties of Eu 3+ -Doped Oxide Glasses for Optical Fiber Application.

This study presented an analysis of the TeO ₂ /GeO ₂ molar ratio in an oxide glass system. A family of melt-quenched glasses with the range of 0-35 mol% of GeO ₂ has been characterized by using DSC, Raman, MIR, refractive index, PLE, PL spectra, and time-resolved spectral measurements. The increase in the content of germanium oxide caused an increase in the transition temperature but a decrease in the refractive index. The photoluminescence spectra of europium ions were examined under the excitation of 465 nm, corresponding to ⁷ F ₀ → ⁵ D ₂ transition. The PSB (phonon sidebands) analysis was carried out to determine the phonon energy of the glass hosts. It was reported that the red ( ⁵ D ₀ → ⁷ F ₂ ) to orange ( ⁵ D ₀ → ⁷ F ₁ ) fluorescence intensity ratio for Eu ³⁺ ions decreased from 4.49 (Te0Ge) to 3.33 (Te15Ge) and showed a constant increase from 4.58 (Te20Ge) to 4.88 (Te35Ge). These optical features were explained in structural studies, especially changes in the coordination of ^[4] Ge to ^[6] Ge. The most extended lifetime was reported for the Eu ³⁺ doped glass with the highest content of GeO ₂ . This glass was successfully used for the drawing of optical fiber.