Modal dispersion curves of metal-clad concave lens shaped waveguides and their comparative study

Abstract

This paper presents a comparative study of dispersion characteristics of metal-clad waveguides with concave-lens-like cross sections. Using the point-matching method under weak-guidance approximation, the modal characteristic equation is derived and the modal dispersion curves are obtained. The proposed waveguide may be conceived as a distortion of the square waveguide with a transverse compression at one pair of its parallel sides in order to become concave lens shaped. We find that, the effect of the concave lens shaped distortion is to shift the lowest cutoff value (Vc) towards a larger V value, and increases the number of modes. It is also observed that the lowest cutoff value increases gradually with the increase in the compression depth.