Effects of modifier oxides in the nonlinear refractive index of niobium-borotellurite glasses

Highlights: ●Nonlinear refractive index of niobium-borotellurite glasses at VIS-NIR region determined through Z-Scan technique. ●Applying BGO approach to model the experimental nonlinear refractive index dispersion of niobium-borotellurite glasses. ●Investigation of structural changes of niobium-borotellurite glasses performing vibrational spectroscopy. ●Analysis of the effect of transition metal oxides in the molar electronic polarizability. -- Abstract: This work investigates the influence of transition metals oxides (Ta₂O₅ and ZrO₂) on the nonlinear refraction of niobium-borotellurite glasses prepared by melt-quenching technique. The closed-aperture Z-scan technique was used to measure the nonlinear refractive index (n₂) spectrum from 470 nm to 800 nm. Also, the BGO (Boling, Glass, and Owyoung) approach was used to model nonlinear spectra, considering the oxygens present in the sample as the major contribution to the nonlinearity. The samples' molar electronic polarizability was determined to further understanding the effect of the transition metals oxides on the optical properties. Structural analysis was performed by differential scanning calorimetry, Raman and Infrared spectroscopies. The results indicate that although the modifier oxides affect the structural units and glass polarizability, they are not enough to change the behavior of the nonlinear refractive index spectra, being the glass-matrix the main responsible for optical nonlinearity in the system studied here.