Tunable terahertz radiation from arbitrary profile dielectric grating coated with graphene excited by an electron beam

Zhao Tao^a),^b), Zhong Ren-Bin†^a),^b), Hu Min^a),^b), Chen Xiao-Xing^a),^b), Zhang Ping^a),^b), Gong Sen^a),^b), Liu Sheng-Gang^a),^b)

Intensity of radiation wave with frequency at the Brillouin center of the second dispersion band in vacuum (a) and substrate (b) sides versus the asymmetry factor for the two diffraction types, the asymmetry factor is a ₁ for Type I, and it is a ₂ for Type II.