Low contrast buried waveguides index profile reconstruction method considering the evanescent field

This is the authors' abstract. We don't add key points for this paper.

In this work we present a new approach related to the profile reconstruction of graded-index waveguides, based on the inversion of the Helmholtz equation for transversal electric propagation modes from measuring the near field. We used the scalar approximation, but we also consider the evanescent field as key experimental data to be acquired and analyzed. From this, it is possible to obtain a better fitting of the real low-contrast waveguide index profile and get more important information, allowing us to determine at the same time the effective index and the shape of the guidance cross section. Compared with experimental data, it could be possible, in a self-consistent way, to enhance the accuracy of the retrieval information corresponding to the transversal shape of these kinds of waveguides. This procedure also allows us to obtain an effective and absolute refractive index profile instead of the relative determinations that are usually reported in the literature.