Excitation of Surface Plasmon Polaritons (SPPs) at Uniaxial Chiral-Graphene Planar Structure

Graphene has garnered significant interest since its discovery. In graphene, surface plasmon polaritons (SPPs) are excited at frequencies ranging from mid-infrared to terahertz, which is not possible with traditional plasmonic materials. In this manuscript, numerical analysis of SPPs at uniaxial chiral-graphene planar structure is delineated. The surface conductivity of monolayer graphene is modeled by Kubo formulism. The dispersion relation is obtained analytically by applying impedance boundary conditions on the tangential field components. Extended electromagnetic theory is utilized to solve the analytical problem. The variation in effective mode index under the different values of chirality and graphene features (chemical potential, relaxation time, and number of layers) for three types of uniaxial chiral media, i.e., \({\varepsilon }_{t}\) ${\epsilon }_t$ > 0, \({\varepsilon }_{z}\) ${\epsilon }_z$ > 0, \({\varepsilon }_{t}\) ${\epsilon }_t$ < 0, \({\varepsilon }_{z}\) ${\epsilon }_z$ < 0 and \({\varepsilon }_{t}\) ${\epsilon }_t$ > 0, \({\varepsilon }_{z}\) ${\epsilon }_z$ < 0 are analyzed in the THz frequency regime. It is found that the effective mode index is very sensitive when both longitudinal and transverse components of permittivity exhibit opposite signs as compared to other two cases. To confirm the presence of SPPs for the suggested structure, the normalized field distribution for uniaxial chiral medium is also studied. The present work holds promising potential for the fabrication of high-density nanophotonic chips at THz frequency regime.