In this work, we investigate the spectroscopy properties of neodymium doped tungsten-tellurite glasses prepared in ambient and O 2-rich atmospheres. A conversion of TeO 4 to TeO 3 units was caused by the addition of Nd 3 þ into the glass, which was confirmed by absorption spectra and by Judd-Ofelt parameter behavior. The relaxation of the 4 F 3/2 level is dominated by radiative decay and cross-relaxation between Nd 3 þ and Nd 3 þ ions. The energy transfer from Nd 3 þ to the hydroxyl group is negligible when compared to the cross-relaxation. The luminescence quantum efficiency values of the 4 F 3/2 level decreases as the Nd 3 þ concentration increases, independently if determined by the Judd-Ofelt method or by the thermal lens technique. The observed reduction in the IR absorption associated to OH groups was not effective to improve the luminescence quantum efficiency.

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Thermal lens (TL) spectrometry was applied to soybean biodiesel samples, in order to assess the behavior of their thermo-optical properties during the preparation before and after the washing process. The study was based on the thermal diffusivity parameter, which is highly sensitive and is related to the chemical composition of the sample. The results showed a difference of approximately 20% between the initial (unwashed) and the final (washed) steps of biodiesel production. This behavior indicates that the residue of the biodiesel production influences the thermal diffusivity value. Consequently, TL spectrometry can be a useful methodology for certifying the quality of biodiesel during production.

We studied the influence of different lattice modifiers (Nb 2 O 5 , Bi 2 O 3, or TiO 2) on the nonlinear refractive index of a tellurite glass matrix by using the Z-scan technique. Based on the ability of the lattice modifiers to decrease the band-gap energy while simultaneously increasing the linear refractive index of the TeO 2-based glass, we investigated how these modifiers affect the nonlinear refractive indices. All studied glass presented high nonlinearities, and the addition of lattice modifiers made only a small contribution to increasing magnitude. These results could be explained through the observation of the band-gap energy reduction, which is related to the increase in the non-bridging oxygen content with the addition of the lattice modifier. The increase in the refractive index nonlinearity is explained by the optical basicity and the high electronic polarizability of the modifiers ions.