Weak Guidance Modal Analysis and Dispersion Curves of an Infrared Lightguide Having a Core Cross Section with a New Type of Asymmetric Loop Boundary

Abstract

We make an analytical investigation of the modal characteristic equation of an infrared lightguide having a guiding region whose cross section has a new type of asymmetric loop boundary. We choose new coordinates (ξ,η,z) instead of (r,θ,z), and assuming that the propagation is along the z direction, we use the boundary conditions under the weak guidance approximation to obtain the modal characteristic equation and cutoff equation. From the cutoff equation we get the number of modes propagated in the guiding region for a given size of the guiding region. From the characteristic equation the dispersion curves are obtained in the second telecommunication window at λ0=1.3 and 1.55 μm. This analysis is applicable to dielectric waveguides in the microwave region also.