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)

(a) Dispersion curves for the symmetrical (the magenta dashed curves) and asymmetrical (the blue solid curves) trapezoidal grating, where b is equal to 0.2, a ₁ is equal to 0.1, and other parameters are the same as that used in Fig. 2 . (b) Radiation spectra of the symmetrical (the dashed curves) and asymmetrical (the solid curves) trapezoidal gratings.