Tunable Cherenkov Terahertz Graphene Surface Plasmon Generation in Graphene Sheet by a Moving Relativistic Electron Beam

The moving electron beam first excites the (Graphene surface plasmons) GSPs by phase matching, and then GSPs are transformed into radiation in dielectrics when meeting the Cherenkov radiation condition. A relativistic electron beam is passing over a graphene sheet deposited on a glass substrate, excites the tunable and coherent graphene surface plasmons (GSPs), and is transformed into terahertz radiation via Cherenkov interaction, whose frequencies lie in the THz regime. The interaction between electron beam and graphene plasmons takes place, when the beam velocity reaches to the phase velocity of the graphene surface plasmons, and their fields cause the density bunching of the beam. The electron bunch modulates the current which is the source of tunable and coherent terahertz radiation. The growth rate of THz graphene plasmons can be tuned by changing the thickness of the graphene layer and also the energy of the electron beam. This proposed study opens a new way for developing a tunable and coherent source for THz radiation generation which covers the whole range of THz spectrum.