Characteristics of hybrid surface plasmon polaritons at a chiral graphene metal interface in cylindrical waveguides

Mariam Saeed,Majeed A S Alkanhal,Yasin Khan,Abdul Ghaffar

doi:10.1007/s11082-021-03219-w

Abstract

A detailed theoretical analysis of the hybrid surface plasmon mode generation and propagation at a chiral graphene metal (CGM) interface for a cylindrical structure is presented. The conductivity of graphene is modeled using the Kubo formalism and the dispersion relation for the hybrid surface waves is computed on the basis of the Kubo formalism and impedance matching boundary conditions. The hybrid mode consisting of lower and upper plasmon modes is witnessed due to the presence of the chiral medium. The frequency band gap between the lower and upper plasmon modes is found to be sensitive and tunable with respect to the chiral strength, radial distance of the waveguide, and chemical potential of graphene. The propagation length and effective refractive index can also be modulated by varying the chiral strength and chemical potential. For very high values of chirality and biasing voltage, the Goos–Hänchen effect is observed at the CGM interface. The cutoff values of chiral strength as a function of normalized frequency make the proposed structure applicable for chiroptical and chemical sensing and enantiomeric detection in the THz frequency regime.

Highlights

Chiral-filled plasmonic waveguides have drawn the attention of the research community in recent years due to their ability to act as sensors in various fields [1]
Numerous studies based on chiral waveguides having different configurations, such as chiral slabs bounded by a perfect conductor medium [9], planar chiral structures [10], chiral graphene metal (CGM) planar structures [11], chiral-filled double-layer graphene planar structures [12], and chiral-lined metal cylinders [13], have revealed the existence of hybrid plasmon modes instead of only TM or TE modes
The dispersion curve plotted between the incident frequency ω and propagation constant β/ko under special conditions (i.e., ξ = 0.0 Ω-1 and permittivity of cladding region as εm= 1.2εo) converges to only a single TM plasmon mode, which is quite similar to the surface plasmon modes propagating in the dielectric-filled graphene-coated cylindrical waveguide embedded in a dielectric environment, as presented in Fig. 3 [19]

Summary

Introduction

Chiral-filled plasmonic waveguides have drawn the attention of the research community in recent years due to their ability to act as sensors in various fields [1]. Numerous studies based on chiral waveguides having different configurations, such as chiral slabs bounded by a perfect conductor medium [9], planar chiral structures [10], chiral graphene metal (CGM) planar structures [11], chiral-filled double-layer graphene planar structures [12], and chiral-lined metal cylinders [13], have revealed the existence of hybrid plasmon modes instead of only TM or TE modes This happens due to the coupling between the left-circularly polarized (LCP) and right-circularly polarized (RCP) waves in the chiral medium. The influence of the chiral strength, chemical potential of graphene, radius of the cylinder, and refractive index of the chiral material on the dispersive behavior of surface plasmons is presented by generating and analyzing numerical results in detail . All the formulations contain exp(jωt), which represents the time dependence factor

Formulations and Methodology

Results and Discussion

Conclusion