Germanium concentration effects on the visible emission properties of Er3+ in tellurite glasses

Highlights: • High refractive index that is suitable for photonic applications. • Considerable variations of Erbium's emission properties induced by the germanium incorporation in the host vitreous matrix. • Improvement of the optical quality for oxide-based glasses. • Systematic Judd-Ofelt's analysis for Er3+. • Favorable thermal stability making possible the fiber fabrication by preform thermal drawing. The influence of different Germanium dioxide concentration on the structural, thermal, optical and spectroscopic properties of Er³⁺ doped tellurite glasses was carefully investigated. The glasses were prepared by melt-quenching technique. The samples were characterized by UV–visible–near-infrared spectroscopy, downshift emission spectroscopy, Raman spectroscopy, lifetime of green emission and up-conversion under near-infrared laser diode excitation at 975 nm. The Judd-Ofelt analysis was performed based on the absorption spectra of the glasses in order to obtain the Judd-Ofelt parameters (${\text{Ω}}_{\lambda }$), radiative transition rates, radiative lifetimes and quantum efficiency. The solubility of Er³⁺ into the host vitreous matrix, the enhancement in the luminescence intensity and improvement in the thermal stability ($\ge$ 100 ^∘C) of the glasses was verified on introducing GeO₂.