Steering Smith-Purcell Radiation Angle in a Fixed Frequency by the Metal Grating

One of the compact and cost-efficient manner to generate high-intensity THz radiation sources is the Smith-Purcell (SP) effect, which brought up by a beam of charged particles passing parallel over a periodic structure. In this study, a high-duty-cycle metal grating has been proposed as a means of achieving direction-tunable SP radiation waves at a fixed frequency. This is accomplished by changing the speed of the electron beam without adjusting the geometrical parameters or introducing additional coupling structures. The results suggest that the radiation angle can be controlled in a range of 100° by varying the electron beam velocity from the perspective of theoretical analysis, analytical simulation and Particle-in-Cell (PIC) simulation. The discovery not only addresses the challenge of the spectrum scatter in the direction of radiation when the electron velocity fluctuates but also presents a new way to control electron-beam-induced emission in the near-field region. Furthermore, the results pose promising prospects for compact, tunable, and efficient sources of light and particle detectors.