Interaction of an electromagnetic wave with a cone-shaped invisibility cloak and polarization rotator

Abstract

A cone-shaped cloak whose cross section gradually increases along the axial direction ($z$ direction) is proposed in this paper. We present full wave analysis of this cloak in response to electromagnetic waves, showing that a perfect conical cloak can support the propagation of any kind of fields. In addition, the reduced set of cloaking parameters is derived for azimuthally invariant $\left(\partial /\partial \phi =0\right)$ incident fields. The advantage of this simplified cloaking structure is that all the components of material parameters are spatially invariant with relative magnitude larger than one. Hence, conical cloak with small scattering is physically realizable within a wide band of frequency for this specific type of incident fields. Finally, we apply similar transformation to achieve a polarization rotator which can arbitrarily control the polarization of the electromagnetic wave getting through. The proposed design provides a practical way to realize invisible cloak and some other electromagnetic devices, especially in the conditions that the source distribution is rotationally symmetric.