Study on the Electron Beam Excitation of Graphene Surface Plasmon Polartions

Graphene surface plasmon polaritons have been widely used in terahertz devices in modern science and technologies. In this paper, the excitation of graphene surface plasmon polaritons by perpendicularly and parallel moving electron beams is investigated in details by using Maxwell equations and boundary conditions. The theoretical analysis and numerical calculations show that graphene surface plasmon polaritons excited by perpendicular electron beam contain plenty of frequency components which attenuate along with propagation, whereas those excited by parallel electron beam are coherent and tunable, without attenuation along with propagation. The largest power of the excited graphene surface plasmon polaritons can be obtained by optimizing the electron beam energy and the chemical potential of the graphene sheet. And the further study show that graphene surface plasmon polaritons can be excited and amplified by continually moving electron beam when the current density of the beam is large enough. These results are of significance for the applications of graphene in terahertz devices.