Optical properties of reactively sputtered TeOx amorphous films

We report on the linear optical properties of TeOx films deposited by radio-frequency reactive sputtering on fused-silica substrates. The oxygen stoichiometry ranges from x = 1.95 to x = 2.75, as experimentally determined by Rutherford backscattering. The complex dielectric function of TeOx samples has been measured in the range from lambda = 260 nm to lambda = 1700 nm by variable angle spectroscopic ellipsometry. All samples are transparent in the visible and near infrared. Regarding the refractive index measured at lambda = 1.5 microm, delta n variations from 0.5% to 7% were found, with the general trend monotonically decreasing with respect to the oxygen content. This opens the possibility to easily implement TeOx-based multilayer structures, with a fine tuning of the index, which could be of particular interest for applications in optical communications.