Weak guidance modal behaviour, cutoff condition and dispersion curves of a waveguide with a guiding cross-section bounded by two Archimedian spirals

Abstract

This paper describes an analytical study of modal cutoff conditions and dispersion curves of an optical waveguide with a core cross-section bounded by two Archimedian spirals. The modal characteristic equation and cutoff conditions of the proposed waveguide have been obtained using the boundary conditions under the weak guidance approximation. The present analysis shows that if the cross-section of the planar waveguide is bent along a spiral such that one side is wider than other, this results in a reduction of the number of sustained modes.