Plane wave diffraction by uniaxial chiral slabs

-- The Uniform Asymptotic Physical Optics (UAPO) approach is here adopted to solve the diffraction problem arising from the interaction of an incident plane wave and a truncated uniaxial chiral slab with the optical axis perpendicular to the surface. UAPO solutions in the context of the Uniform Theory of Diffraction (UTD) [1] have been derived for many diffraction problems [2, 3]. They are attractive from the engineering point of view since they do not require solving differential/integral equations. Moreover, although they result from an analytical procedure, they possess the same simplicity of use associated to the UTD heuristic solutions. The UAPO approach benefits from the simple formulation of electric and magnetic PO equivalent surface currents, but also includes some well-known drawbacks due to the PO approximation. The effectiveness of the UAPO solutions has been proved by means of "in house" and commercial numerical tools [2, 3]. The first step of the UAPO approach concerns the evaluation of the elements of the reflection and transmission matrices in accordance with [4]. Such matrices relate the parallel and perpendicular polarized components of the reflected and transmitted electric fields to the counterparts of the incident electric field on the uniaxial chiral slab. They are indispensable to the computation of the Geometrical Optics (GO) field that is successively used to determine the electric and magnetic PO equivalent surface currents working as sources in the radiation integral. This last is properly manipulated by taking advantage of useful approximations, mathematical computations and integral representations. The result of the analytical procedure is the UAPO diffracted field, which is expressed in terms of the UTD transition function [1] and the GO response of the structure. The proposed solution is able to compensate the GO field discontinuities at the shadow boundaries for the reflected and transmitted fields.