A study of nonlinear optical properties in Bi2O3–WO3–TeO2 glasses

A series of bismuth tungsten tellurite glasses were prepared and their densities, linear refractive indices and transmission spectra were measured. The optical bandgaps Eopt and Urbach energies Ee of glasses were obtained from ultraviolet absorption edges. Both the optical gap (Eopt) and the band tail (Ee) are behaving oppositely. As the value of Eopt decreases with increasing WO3 content, the degree of disorder increases which causes more defects or localized states resulting in deep localized in the bandgap with the tailing increased. Z-scan technique was carried out to investigate the third-order nonlinear optical properties of Bi2O3–WO3–TeO2 glasses. The third-order optical nonlinearity increases with decreasing the optical bandgap Eopt, since a increase of WO3 content can provide the non-bridging oxygen ion content.