Enhanced terahertz Smith-Purcell radiation using an inclined flat electron-beam to drive Fabry-Pérot resonator arrays

Besides transition radiation (TR) and synchrotron radiation (SR), Smith-Purcell radiation (SPR) is a simple method to generate powerful terahertz emission. Yet, as the distance from grating surface to electron trajectory increases, the SPR intensity decays exponentially due to the effective interaction range[1] ${h_{\operatorname{int} }} = \frac{\lambda }{{4\pi }}\beta \gamma $. The radiation efficiency is greatly reduced beyond the effective interaction range especially for large diameter beams. To increase the coupling efficiency, an inclined flat electron beam is used in this paper. Meanwhile, the Fabry-Pérot resonator arrays take place of the ordinary grating to achieve higher radiation power. This new method of SPR reduces the requirement of electron beam and enhances the radiation intensity. To verify the theory, an electron gun from SJTU is used in experiment, the results of which agree with theoretical analyses and simulations..