A Study of cloak/anti-cloak interactions

Coordinate-transformation-based invisibility cloaking is based on the design of the desired field distribution (which allows rerouting of the impinging energy around the object to conceal) in a fictitious curved-coordinate space containing a “hole”. Exploiting the formal invariance of Maxwell's equations under coordinate transformations it is then possible to translate such distribution into a conventionally flat, Cartesian space, filled by a suitably anisotropic and spatially inhomogeneous transformation medium [1]. It has been shown analytically that, in the limit of an “ideal” cloaking (implying a lossless, anisotropic, spatially inhomogeneous metamaterial, with extreme values of the relative permittivities and permeabilities ranging from zero to infinity), the field cannot generally penetrate from outside to inside, and vice-versa [2,3]. A notable exception to the above picture, however, was recently pointed out by Chen et al. [4], who showed that the field may actually penetrate the cloaked region in the presence of a suitably designed double-negative (DNG) transformation media which can act as an “anti-cloak”.