Dispersion Properties in Uniaxial Chiral–Graphene–Uniaxial Chiral Plasmonic Waveguides

Abstract

Plasmonic-based devices attracted considerable attention in the scientific community. However, noble metals provide less tunability to control the electromagnetic (EM) surface wave. Therefore, it is imperative to design dynamically tunable plasmonic devices. In this manuscript, a theoretical model is developed for a graphene-filled waveguide surrounded by uniaxial chiral material (UACM). The complex conductivity of graphene is modeled with the help of the eminent Kubo formula. By applying boundary conditions at the interface, the characteristic equation is derived to investigate the behavior of the normalized propagation constant for the proposed waveguide. The variation in normalized propagation constant under the different parameters of graphene such as chemical potential, relaxation time, number of layers as well as values of chirality for different cases of UACM, i.e., \({\varepsilon }_{\text{t}}\) > 0, \({\varepsilon }_{\text{z}}\)> 0, \({\varepsilon }_{\text{t}}\) < 0, \({\varepsilon }_{\text{z}}\) < 0 and \({\varepsilon }_{\text{t}}\) < 0, \({\varepsilon }_{\text{z}}>\) 0 is analyzed in the THz frequency range. This study reveals that the normalized propagation constant is very sensitive when both longitudinal and transverse components of permittivity exhibit a negative sign (\({\varepsilon }_{\text{t}}\) < 0, \({\varepsilon }_{\text{z}}\) < 0) as compared to the other two cases. It is observed that all three types of UACM have different cutoff frequency ranges. Field profile of UACM such as \({E}_{\text{z}}\) and \({H}_{\text{z}}\) also studied to confirm the existence of SPP. The present work holds promising potential to offer a new platform graphene-UACM-based plasmonic devices that can be utilized to fabricate waveguides that are dynamically tunable in different THz frequency regions.