Terahertz Metal-Graphene Composite Plasmon Waveguides Combining Strong Field Confinement with Low Cross-Talk: A FEM Study

Terahertz waves have great potential in next generation communications due to their broadband and high channel capacity. To integrate terahertz wireless links into fiber infrastructure, it is necessary to guide terahertz waves below the diffraction limit. To meet the demand for compact terahertz devices, here a metal-graphene composite plasmonic waveguide is proposed to realize strongly confined modal fields. The dependence of waveguide sizes and material properties on the mode characteristics of the proposed waveguide are studied by the finite element method. The results show that strongly confined modal fields could be achieved by changing the Si gap, and the normalized mode area could be as small as 3.84 × 10⁻⁶. Furthermore, the modal properties could be tuned by changing the Fermi energy of graphene. The investigation on cross-talk between adjacent structures shows that the integration spacing of this waveguide is less than 0.1 μm, indicating a high integration density. The proposed structure is capable of realizing various subwavelength functional terahertz devices that may meet the future demand of terahertz communication.