Radiation modes in tapered slab waveguides via the introduction of conducting surfaces

摘要

Planar dielectric waveguides having non parallel surfaces usually cannot maintain all the modes along with the propagation direction and thus give rise to radiation modes. The analysis of such modes presents considerable theoretical difficulties. A strategy has been made to deal with the problem by assuming conducting surfaces at a certain fixed distance from the tapered guiding surfaces. We then proceed to the dispersion curves of such structures and find that the modes are considerably affected by a near approach of the conducting layers. It is observed that the radiating modes emerge after some fixed frequency and its phase velocity varies for different β values. Finally as the metallic surfaces more away to a very large distance, we may obtain information about the characteristics of the radiating modes of the actual tapered planar waveguide.