THE PROPAGATION PROBLEM IN A BI-ISOTROPIC WAVEGUIDE

We investigate the problem of deflning propagating constants and modes in metallic waveguides of an arbitrary cross section, fllled with a homogeneous bi-isotropic material. The approach follows the guidelines of the classical theory for the isotropic, homogeneous, lossless waveguide: starting with the Maxwell system, we formulate a spectral problem where the square of the propagation constant shows up as the eigenvalue and the corresponding mode as the eigenvector. The di-culty that arises, and this is a feature of chirality, is that the eigenvalue is involved in the boundary conditions. The main result is that the problem is solvable whenever the Dirichlet problem for the Helmholtz equation in the cross section is solvable and two technical hypotheses are fulfllled. Our method, inspired by the null-fleld method, is quite general and has a good potential to work in various geometries.