Metasurface-bounded open cavities supporting virtual absorption: free-space energy accumulation in lossless systems.

We investigate an anomalous scattering phenomenon exhibited by a lossless system based on metasurfaces. Electromagnetic energy is neither reflected nor transmitted but stored within the system to be available again at a different time. We analytically derive the proper excitation conditions and verify the response of the system through a proper set of full-wave simulations, demonstrating the key role of the metasurface in enabling such a zero-scattering condition. The practical feasibility and the opportunities offered by the proposed metasurface-based system may open the door to the design of virtual absorbers with dynamic properties in energy absorbing, storing, and releasing.

Efficient and wideband horn nanoantenna.

In this Letter, we present the design of a horn nanoantenna working at near-IR frequencies. The proposed layout consists of an Ag-air-Ag nanotransmission line terminated in a tapered horn. The antenna design is validated through proper full-wave numerical simulations, taking into account actual dispersion and losses of the involved materials. The numerical results show that the designed nanohorn is matched over a broad range of frequencies (more than 50% of fractional bandwidth) and radiates efficiently in the same frequency band (the realized gain is greater than 10 dBi). Such promising results may find application in different technical and scientific fields, ranging from smart lighting to optical wireless communications.

Plasmonic cloaking for irregular objects with anisotropic scattering properties.

Here we extend the plasmonic cloaking technique to irregularly shaped objects with anisotropic scattering response. The scattering-cancellation approach to cloaking [A. Alù and N. Engheta, Phys. Rev. E 72, 016623 (2005)] has been extensively applied in the past to symmetrical geometries and canonical shapes. However, recent papers have raised some doubts concerning the fact that its use may not be as effective when dealing with strongly anisotropic and noncanonical geometries. Our goal here is to extend the plasmonic cloaking technique to irregular obstacles and to show that proper cloak design may provide a significant and uniform scattering reduction, independent of angle of incidence, position, and polarization of the illumination. We investigate how the volumetric effect of scattering cancellation provided by plasmonic media may drastically suppress the scattering for these irregular geometries independent of the illumination angle, and we shed some light on the physical mechanisms and the design rules at the basis of this cloaking technique when applied to objects whose scattering properties are dependent upon polarization and angle of incidence.