Leaky-wave modes and their role in the numerical evaluation of the field excited by a line source in a non-symmetric, inhomogeneously layered, slab waveguide

Abstract

The canonical problem of the line-source excitation of planar, open-waveguide configurations is investigated numerically. In the spectral description, the excited electromagnetic field is determined by the location and the nature of the singularities (poles and branch points) of its spatial Fourier spectrum taken with respect to the axial coordinate, in so far they are located on the physically acceptable sheet of a multi-sheeted Riemann surface. In subsequent computations, the spatial Fourier contour is deformed in an appropriatedly chosen path that is situated on various sheets of the Riemann-surface. In this process also poles, located on non-physically acceptable sheets, will be circumvented and consequently will play a role in the excited field. The properties of the field distributions corresponding to all these poles, surface-wave and leaky-wave modes, and where possible their interrelationship, are discussed for various planar-waveguide configurations. Numerical results will be given and the role of leaky-wave modes in the excited field will be discussed in detail.