Use of an Epsilon-Near-Zero Region Comprised of a Graphene Strip-Silica Stack for Designing Cloaking and Reflection Devices

Abstract

Super cloaking and reflection functionalities are designed using alternating layers of a graphene strip (GS)-silica stack at $1.55~\mu \text{m}$ . First, a zero index material (ZIM) by utilizing the mentioned structure is achieved that according to the effective medium theory, it exhibits an effective permittivity which can be tuned through filling factor, the dielectric material, and Fermi energy of GSs. Afterward, the super cloaking and reflection functionalities for different polarizations are obtained in such a medium depending on the selection of boundary conditions and inclusions. Simulation results reveal that these functionalities exhibit an extremely broadband operation, and additionally, they are robust against the oblique incidence and inclusion shape that the latter feature cannot be achieved through a monolayer graphene. Furthermore, a monolayer graphene provides a moderate bandwidth for the cloaking functionality. Such functionalities using the ZIM provide a much better performance in comparison to other ZIMs made of thin film oxides. In addition, the ZIM property in thin film oxides is controlled chemically, and it is limited to a certain frequency range, whereas the ZIM feature in this paper can be tuned either electrically or chemically, and moreover, it can be set in different frequency ranges.