Observation of graphene surface plasmon polaritons excited by free electron beam

In previous work, we propose to develop a novel kind of terahertz radiation source which utilizing free electron beam to excited graphene surface plasmon polaritons (GSPPs) combining vacuum electronics and new 2D material graphene. The previous theoretical analysis show that this coherent radiation source can be tuned covering almost whole THz frequency range and work at room temperature. In this paper, we demonstrate the conductivity mapping of GSPPs with free electron beam excitation using TDS system. The characteristics of GSPPs can be derived from the calculated conductivity results and be compared with the theoretical Drude model, which would guide the next step of the experiment to realize the new kind of THz source.