The propagation of s-polarized surface plasmon polaritons (SPPs) was investigated in a monolayer graphene sheet surrounded by two dielectric media on each side, so that one or both sides of the media were linear or nonlinear with Kerr-type nonlinearity. The plasmonic properties including the wave propagation index neff, the penetration depth, the time-averaged power flow and the spatial profile of electric and magnetic fields were calculated for the following structures: Linear medium/Graphene/Linear medium (L/G/L), Nonlinear medium/G/L (NL/G/L) and NL/G/NL. The analysis of the nonlinear coefficient effect on the SPP properties showed that increasing the nonlinearity in NL/G/L enhanced neff. However, for a smaller difference between the nonlinearity of layers, neff decreased in NL/G/NL. By comparing between the proposed structures, it was found that while large values of neff can be obtained from L/G/L, its frequency confinement is smaller than that of NL/G/L and NL/G/NL. Furthermore, NL/G/L and NL/G/NL were able to support localized nonlinear modes, leading to enhanced frequency confinement of transverse electric (TE) waves in the presence of nonlinearity. Increasing the nonlinearity in NL/G/L confined the spatial profile of the electric field near the graphene interface, indicating the existence of surface plasmon solitons. The influence of the graphene chemical potential μ on the plasmonic properties of the structures was also investigated. In this case, it was found that the plasmonic properties can be controlled by μ. Our calculations may solve the difficulties in TE surface plasmons for application in optics and plasmonics.

In this study, a three-layered system consisting of a Kerr-type nonlinear medium confined between two semi-infinite linear media is considered. The nonlinear medium is a parallel-plate graphene waveguide with a thickness of d. Analytical expressions for dispersion relation and the field profiles in terms of Jacobi elliptic functions are performed and solved numerically. Plasmonic properties such as the effective mode index ( ), localization length ( ) are studied. It is found that and of the system can be tuned by chemical potential of graphene, arising from its tunable optical conductivity. Localization of transverse electric (TE) surface waves increases with increasing the medium nonlinearity, providing deep-subwavelength confinement. Moreover, increasing d from 1 to 130 nm enhances the mode confinement. We also apply our scheme to a bilayer graphene (BLG) waveguide, allowing for predicting the existence of TE modes. Our results show that the TE modes in BLG are more pronounced than those in single-layer graphene. Therefore, the BLG structure is found to be promising in the fabrication of optical devices with TE plasmons.

No abstract

No abstract

No abstract