Optical functions of (x)GeO2:(1-x)SiO2 films determined by multi-sample and multi-angle spectroscopic ellipsometry.

Thin films of (x)GeO2:(1-x)SiO2, 0≤x≤0.4, were fabricated via the sol-gel technique. Many applications of optics and photonics can benefit from the knowledge of the optical dispersion relationship of this ubiquitous binary ceramic material. The optical properties of the homogeneous and amorphous silica-based films were derived by spectroscopic ellipsometry (SE) with a multi-sample and multi-angle technique. The physical model used in SE has been rigorously verified. A simple, yet reliable, method is described to produce a dispersion-composition surface for visualizing, and hence, predicting refractive indices of the films. The Sellmeier model was effectively used to describe the optical dispersion properties of the GeO2:SiO2 films for a range of wavelengths from 210 to 1700 nm. Dispersion parameters were determined to evaluate the change in the compositional-dependent dispersion characteristics. In addition, the material dispersion coefficient and zero-dispersion wavelength were found to vary with x.