Electron beam exictation on doped graphene plasmon for generation coherent radiation

Summary form only given. In this paper, we study the excitation of non-relativistic electron beam with some velocity passing on top of a doped graphene layer (see Figure 1 below). We calculate the excitation energy for the plasmon on the graphene, and it is found that the required energy is 3 orders of magnitude smaller as compare to normal metallic plasmon. The main reason of such reduction will be explained. In bulk metals, for a reasonable wave number (e.g. 40μm^-1), this usually translates to high, relativistic electron-energies in the order of keVs (e.g. silver: 63.2keV; aluminium: 427keV). In graphene, however, due to the fact that (i) graphene is a thin film of vanishing thickness, and (ii) graphene has a non-classical scaling of the plasma frequency with respect to electron density, the electron-energies required to excite plasmon of the same β are non-relativistic and remarkably lower in the order of eVs (e.g. graphene (doped to 0.2eV). Its application as a coherent radiation source will also be discussed.