Transformation-based cloak/anti-cloak interactions: A review

The intriguing concept of anti-cloaking was originally introduced within the framework of transformation optics (TO) as a countermeasure to invisibility-cloaking, i.e., to restore the scattering response of a cloaked target. More recently, its relevance was also suggested in applications to sensor invisibility, i.e., to strongly reduce the scattering response while maintaining the field-sensing capabilities. In this chapter, we review our recent studies on two-dimensional (cylindrical) and three-dimensional (spherical) canonical scenarios. More specifically, via generalized (coordinate-mapped) Bessel-Fourier and Mie-series approaches, we address the analytical study of plane-wave-excited configurations featuring a cylindrical or spherical object surrounded by a TO-based invisibility cloak coupled to an anti-cloak via a vacuum layer, and explore the various interactions of interest. Via a number of selected examples, we illustrate the cloaking and field-restoring capabilities of various configurations, with special emphasis on the scattering versus absorption tradeoff, as well as possible ideas for approximate implementations that do not require the use of double-negative media.