A Theoretical Investigation on the Role of Surface Plasmon Excitation in the Cloaking and Protection of Gold Cylindrical Rods Using Metallic Layers of Different Materials

This work investigates the excitation of plasmons in the common region between two coaxial cylindrical waveguides nested within each other, utilizing planar electromagnetic waves. The structure under consideration comprises a metallic antenna shielded with another metallic thin layer, both metals assumed to be cylindrical symmetrically without a gap and in a concentric configuration. The conductivity of the metals is evaluated using the Drude theory. An incident electromagnetic wave in B-mode with \(B_z\ne 0\) is radiated onto the mentioned antenna. By employing wave scattering theory and solving the field equations in each region, including the vacuum, outer metallic thin layer, and inner metallic core, the surface charge density resulting from the presence of surface plasmons at the interface between the inner metallic core and the outer metallic layer, as well as between the metallic layer and the vacuum region, is calculated and analyzed. The variations in surface plasmon density at the first interface (the common boundary between the two metals) and the interface between the metal and vacuum are investigated concerning changes in the incident wave frequency and the radii of the antenna layers. It is demonstrated that the excitation of plasmons occurs most significantly in the frequency range where the conductivities of the inner metallic core and the metallic layer have opposite signs, leading to synchronization between surface plasmons.