Optical absorption and emission properties of Nd 3+ in TeO 2–WO 3 and TeO 2–WO 3–CdO glasses

Abstract

Effects of WO 3 and CdO on the spectroscopic properties of Nd 3+ doped tellurite glasses were investigated. The optical band gaps and Urbach energies of the samples were determined using the dependence of the absorption coefficient on the photon energy. The Urbach energies were found to vary from 0.18 to 0.25 eV as the WO 3 content in the binary glasses decreased from 20.0 to 10.0 mol% while the optical band gap of the same glasses did not show an appreciable dependence on the glass composition. Judd–Ofelt ( Ω t ) parameters were calculated from the optical absorption spectra measured at room temperature. In all the glasses the J–O parameters follow the same trend as Ω 2> Ω 6> Ω 4. The J–O intensity parameters were used to compute the radiative properties such as the radiative transition probabilities ( A ed ), branching ratios ( β) and radiative lifetimes ( τ r ) for all the possible fluorescence bands. The fluorescence spectra obtained upon 805.2 nm excitation exhibited an intense emission band centered at 1064 nm ( 4F 3/2→ 4I 11/2) and two weak bands at 910 nm ( 4F 3/2→ 4I 9/2), and 1340 nm ( 4F 3/2→ 4I 13/2). The stimulated emission cross-section for the 1064 nm emission was determined using the emission spectra. The highest gain bandwidth ( σ e ×Δ λ P ) was determined to be 155.4 for the 0.79TeO 2–0.15WO 3–0.05CdO ternary glass composition, which could be more useful as promising material for the design and development of fiber amplifiers and lasers.