▎ 摘　　要

A new type of plasmonic waveguide based on a graphene-coated V-groove structure which can achieve better subwavelength confinements and longer propagation compared to the conventional metal waveguide is proposed. By dynamically altering the chemical potential of graphene, graphene surface plasmon polaritons (GSPPs) multiple modes of the hybrid graphene-coated waveguide can be reached. And the mode field energies can be well confined in the V-groove or the waveguide. The mode confinement becomes weaker and the propagation length gets longer as the chemical potential of graphene increasing. In addition, the mode propagation can be changed by adjusting the radius of the waveguide and the frequencies and the higher mode is achieved at the same time. The finite element method (FEM) has been employed to study the mode distributions and electromagnetic responses of our designs at mid-infrared frequencies. Those proposed structures may pave a way for the further development of ultra-compact, fast-tunable and long-propagation devices in the infrared region (IR).