Three-dimensional Gaussian beam reflection from short-circuited isotropic ferrite slab

The plane wave spectrum analysis is extended to the study of three-dimensional Gaussian beam propagation and scattering. The reflection of a three-dimensional circular Gaussian beam from a parallel-sided ferrite slab, backed by a ground plane, is then investigated. The beam field is represented by an angular continuous spectrum of plane waves. Using the Fresnel reflection coefficients of the short-circuited slab for both perpendicular and parallel polarizations, a paraxial approximation for the reflected beam field is derived. It is found that after reflection from the short-circuited slab, the circular Gaussian beam becomes, in general, an elliptical Gaussian beam, and the beam axis is displaced from the position predicted by ray optics. For the thin slab case, approximate formulas for the phase center difference and the lateral shift are determined. The relevance of these results to a new method of ferrite measurement is explained