EDGE DIFFRACTION IN AN ARBITRARY ANISOTROPIC MEDIUM. I

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Abstract
Diffraction by a perfectly conducting half-plane embedded in a transversely unbounded region filled with a uniform, lossless but arbitrarily anisotropic medium characterized by a Hermitian dielectric tensor ε is studied. Formal solutions in terms of a plane-wave modal superposition (with the modal amplitudes determined via the Wiener–Hopf technique) are obtained. Asymptotic (short-wavelength) contributions (saddle-point contributions as well as contributions due to intercepted singular points) are considered. The asymptotic results are then cast into invariant, ray optical forms, amenable to a distinct physical interpretation.Mode coupling at the boundary gives rise to diffracted (lateral) waves as well as to geometric-optical (incident and reflected) waves. In addition to the "conventional" radially diffracted waves, one observes "secondary" lateral waves generated by the edge. In the short-wavelength limit the edge behaves as a virtual line source whose magnitude is proportional to the total (direct and lateral) field incident upon it. The asymptotic field solutions are valid, subject to the exclusion of some suitably defined transition regions, which are distinctly determined by the geometric-optical expressions. The various (asymptotic) wave constituents are shown to correspond to the anticipated results of geometrical optics.

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