Refractive index and thickness evaluation of monomode and multimode step-index planar optical waveguides using Longitudinal Section Magnetic (LSM) and Longitudinal Section Electric (LSE) formulation

Abstract

In this work, we demonstrate that the LSM and LSE modes formulation is an excellent theoretical tool for determining the refractive index and thickness of the guiding layer in planar optical waveguides with step refractive index profile. Refractive index of transparent materials capable of being deposited as a solid thin layer on a substrate for confining light can be evaluated very accurately. The method can be applied to analyze and design monomode and multimode optical waveguides, unlike the methods proposed so far, including cutoff wavelength region. This wave model only requires the experimental evaluation of the effective indices of the guided modes. In order to verify the developed formulation, the commercial software Olympios was used for theoretical comparison. Polymeric planar optical waveguides were fabricated and characterized. A prism coupling method and the Metricon system were used for effective indices measurements and to compare the accuracy. The experimental evaluation of the thickness was carried out by profilometry. In all cases a complete agreement was obtained for refractive index and thickness between theory and experiments.