Plasmonic cloaking for irregular inclusions using an epsilon-near-zero region composed of a graphene–silica stack

Abstract

A reconfigurable epsilon-near-zero (ENZ) region composed of alternating layers of a graphene nano-ribbon (GNR)–silica stack is designed for realizing a plasmonic cloak at 1.55 μm. The ENZ point is tuned via application of an electrostatic bias to the GNRs. The ENZ region’s boundaries are sealed by Au material with optimized thicknesses in order to avoid light leakage through them. This cloak is robust against the inclusion shape, which is justified by both theoretical and simulation results. Moreover, by selecting a sufficiently large value for the ENZ region length, the associated capacitance takes a very small value; consequently, such a cloak is capable of working in an exceptionally large bandwidth. As a result, this platform is superior in comparison to other platforms made of thin film oxides for realization of an ENZ region. Previous plasmonic cloaks in the literature have some drawbacks, including a narrow bandwidth, sensitivity to the inclusion shape, and a non-reconfigurable operation, whereas the proposed platform overcomes the mentioned issues appropriately. Finally, the robustness of the plasmonic cloak with respect to oblique incidence is investigated, and an acceptable performance is achieved in all angles of incidence while keeping the related bandwidth in an exceptionally large range, indicating that this plasmonic cloak does not have the fundamental limitations of previous plasmonic cloaks in the literature.