Coherent and tunable terahertz radiation from graphene surface plasmon polaritons excited by an electron beam

Although surface plasmon polaritons (SPPs) resonance in graphene can be tuned in the terahertz

regime, transforming such SPPs into coherent terahertz radiation has not been achieved. Here, we

propose a graphene-based coherent terahertz radiation source with greatly enhanced intensity. The

radiation works at room temperature, it is tunable and can cover the whole terahertz regime. The

radiation intensity generated with this method is 400 times stronger than that from SPPs at a

conventional dielectric or semiconducting surface and is comparable to that from the most

advanced photonics source such as a quantum cascade laser. The physical mechanism for this

strong radiation is presented. The phase diagrams defining the parameters range for the occurrence

of radiation is also shown.