Optical absorption and emission properties of Nd in TeO2-WO3 and TeO2-WO3-CdO glasses

Effects of WO₃ and CdO on the spectroscopic properties of Nd³⁺ 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 WO₃ 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 Ω₂>Ω₆>Ω₄. 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×Δλ_P) was determined to be 155.4 for the 0.79TeO₂-0.15WO₃-0.05CdO ternary glass composition, which could be more useful as promising material for the design and development of fiber amplifiers and lasers.