Double-shell metamaterial coatings for plasmonic cloaking

The ideas of employing the unique properties of meta-materials and plasmonic media for cloaking and invisibility applications have been recently suggested and investigated by several groups [1–5], and they may find numerous applications in physics and technology. While many of the recent designs of the cloaking structures are based on the transformation optics and exact formulas [6], the original concept proposed by Alù and Engheta [1] suggests to use simpler plasmonic and metamaterial coatings in order to reduce drastically the total scattering cross-section of an object by relying on a nonresonant scattering cancelation [7]. This approach is based on the observation that, in a certain range of frequencies, the polarization vector in a plasmonic material may be antiparallel with respect to that in a dielectric, implying that a dipole moment of the opposite phase may be induced in a plasmonic shell placed around a dielectric or even conducting object. This scattering-cancelation approach is based on the local negative polarizability of metamaterials, and its realization was recently demonstrated experimentally at microwave frequencies [8], where an array of metallic fins embedded in a high-permittivity fluid was used to create a metamaterial plasmonic shell capable of cloaking a dielec-tric cylinder, with 75% reduction of total scattering width. The recent extensions of this concept are based on the use of multilayered plasmonic shells [9, 10]. In this Letter, we develop further the applications of the multilayered plasmonic cloaks [9, 10] and study the electromagnetic scattering of small particles by employing the structure with a double-shell metamaterial coating (see Fig. 1) that provides simultaneously the shielding of the cloaked volume and substantial reduction of the scattering losses. We demonstrate, by employing realistic parameters that, by using a layer with an epsilon-near-zero material allows to reduce substantially the scattering losses leading to the effect of electric field super-localization when a large amount of energy is concentrated inside a small shell volume. We consider an isotropic cloaking structure (see Fig. 1) composed of two layers of different materials, the simpler version of the multilayered plasmonic shell [9]. The use of two layers of the coating materials allows to avoid the coupling between the object and an external shielding shell of the cloak and to suppress higher-order-mode scattering [10]. By employing this structure, we can achieve two major goals: (i) to realize a screening of a closed spatial region () r a < from an external electromagnetic field, …