Tunable terahertz radiation from arbitrary profile dielectric grating coated with graphene excited by an electron beam |
(a) Frequency at the Brillouin center of the second dispersion band and band gap versus the asymmetry factor a 1. (b) Radiation intensity with frequency at the Brillouin center of the second dispersion band in vacuum and substrate sides versus the asymmetry factor a 1. Other parameters are the same as that used in Fig. 4 . |