A gyrotropic waveguide with dielectric boundaries: the longitudinally magnetised case

Dielectric boundary conditions are applied to the gyrotropic waveguide magnetised along the direction of propagation. The secular equation, which defines the dispersion, is derived in the form of a 4*4 determinant which is used to compute the dispersion curves of a pure YIG guide on a GGG substrate with air above. Computed field profiles permit the classification of the normal modes into two families, one approaching TE characteristics and the other TM. The classification applies only to waveguide materials having a small off-diagonal tensor element delta (or small Faraday rotation).