Modal spectrum of planar dielectric waveguides with quasi-periodic side walls

This work presents an in-depth theoretical analysis of a planar layered dielectric waveguide with periodic side walls. It is shown that, apart from the conventional guided modes for which most of their energy travels within the dielectric dense medium, this guide presents other modes whose energy mostly travels in the air regions inside the side walls or outside them. In particular, the mode with its energy traveling inside the side walls is a low-loss and weakly dispersive mode that could be of interest for practical applications. Moreover, it has been demonstrated that this mode can be strongly excited by a realistic source, which has been done by showing that this mode is the main part of the spectrum radiated by a dipole line located within the air region inside the side walls.