The influence of oxides on the optical properties of tellurite glasses

New tellurite glasses within composition 75TeO₂–5WO₃–15Nb₂O₅–5M_xO_y in mol%, where M_xO_y = (Na₂O, Ag₂O, ZnO, MgO, CuO, NiO, TiO₂, MnO₂), have been prepared using the conventional melt-quenching method. The optical properties of these glasses were estimated by measuring the ultraviolet–visible–near infrared (UV–vis–NIR) spectroscopy and linear refractive indices at different wavelengths. From the absorption edge studies, the values of the optical band gap (E_opt) and Urbach energy (ΔE) were evaluated. The density, molar volumes, molar refraction (R_m), molar polarizability (α_m), metallization criterion (M_c), electronic polarizability of oxide ions (α_O⁻²), and optical basicity (Λ) were estimated. Moreover, the nonlinear refractive index (n₂), third-order nonlinear susceptibility (χ⁽³⁾), and nonlinear absorption coefficient (β) were observed. It was found that the linear and nonlinear refractive indexes increase with decreasing the optical energy gap. (paper)