Determination of Refractive Index Contrast and Surface Contraction in Waveguide Channels Using Multiobjective Genetic Algorithm Applied to Spectroscopic Ellipsometry

The application of spectroscopic ellipsometry for the characterization of UV-patterned channel waveguides to obtain the refractive index contrast and surface deformation profile is presented. Thin films were prepared with organic-inorganic di-ureasils hybrids modified with zirconium tetra-propoxide deposited in silica on silicon substrates. The channel waveguides were produced by direct writing using UV laser radiation. The refractive index contrast and the surface ablation induced by the UV optical signal were estimated by ellipsometry being 4.5 × 10^-3 and 30.5 nm, respectively. The deepness of the surface ablation due to the UV exposition was also estimated by atomic force microscopy measurements that pointed out a value of 31.0 ± 1.0 nm, concordant with the ellipsometric calculations. The near-field intensity technique was used as a support for contextualizing the proposed ellipsometry method for the characterization of refractive index profiles. The estimated refractive index contrast (2.0 × 10^-3) is in a good agreement with the refractive index contrast derived from ellipsometry.