Structural and spectroscopic behavior of Er3 +/Yb3 + co-doped boro-tellurite glasses

• Concentration dependent luminescence behavior of the title glasses was studied.
• Lower Urbach's energy values indicate that, the studied glasses possess minimal defects.
• Higher Ω2 values indicate the higher asymmetry around the RE ion site in the prepared glasses.
• Higher σpE, β, σpE × λeƒƒ values of 1YbErBT glass for 4S3/2 and 4I13/2 levels are useful for high gain laser applications.

A new series of Er3 +/Yb3 + co-doped boro-tellurite glasses with the chemical composition (30 − x − y) B2O3 + 30TeO2 + 16ZnO + 10ZnF2 + 7CaF2 + 7BaF2 + xYb2O3 + yEr2O3 (where, x = 0.05, 0.1, 0.5, 1, 3 and 5; y = 1 in wt.%) have been prepared by conventional melt quenching technique and their structural and spectroscopic behaviors were studied through recording XRD, FTIR, Raman, UV–Vis–NIR and luminescence measurements. The XRD pattern confirms the amorphous nature and the fundamental stretching vibrations of the various borate and tellurite networks were identified through FTIR and Raman spectral analysis. The bonding parameters (β and δ) have been calculated from the band positions of the absorption spectra to identify the ionic/covalent nature. The optical band gap energy (Eopt) corresponding to the direct and indirect allowed transitions, band tailing parameter (B) and the Urbach energy (ΔE) values of the prepared glasses were calculated from the absorption spectral measurements. The Judd–Ofelt (JO) intensity parameters Ωλ (λ = 2, 4 and 6) were calculated through the experimental and calculated oscillator strengths obtained from the absorption spectra and their results were studied and compared with the reported literature. The important radiative parameters such as transition probability (A), stimulated emission cross-section (σPE) and branching ratios (βR) corresponding to the emission transitions 4S3/2 + 2H11/2 → 4I15/2 and 4I13/2 → 4I15/2 have also been calculated and reported in the present work.