Omnidirectional Voltage-Controlled Single-Frequency Smith-Purcell Radiation Based On Low-Coupling Surface Plasmons

Smith-Purcell(SP)radiation is a coherent diffraction radiation(diffraction radiation,DR)obtained by the interaction of an electron beam with a periodic surface.Its radiation characteristics depend to a certain extent on the electromagnetic properties of the periodic structure,and its important advantage is that the required electron beam has no minimum velocity,which makes it possible to manipulate radiation through unique structural design.In recent years,with the development of micro/nanofabrication technology,more and more research has focused on the radiation of micro/nanostructures excited by electrons(metasurfaces,surface plasmons,etc.).Due to the good properties of surface plasmons,it has been possible to manipulate the amplitude,direction of SP radiation and control the frequency of SP radiation using surface plasmons.This paper mainly proposes a model of low-coupling surface plasmon resonance with a constant resonant frequency within a certain period range.By utilizing the single-mode of the Skyrmions on the light cone and the interaction between the electron beam,the radiation direction can be arbitrarily deflected from 0 degrees to 180 degrees by changing the electron velocity(voltage)under the excitation of a low-speed electron beam,without changing other geometric parameters locked at a certain frequency.After the structure is continuously deformed,the radiation direction and power are basically unchanged.The specific research of this paper is as follows:1.Based on the Skyrmions model,the effects of changing the geometric parameters such as the period size,shape,arrangement,and number of turns of the unit on the Skyrmions field mode and sub-wavelength depth are observed.Analyze the reasons for the frequency invariance of the Skyrmions mode from the perspectives of dispersion and coupling.Simplify the process of obtaining the dispersion characteristics of Skyrmions modes in 2D and 3D with different structural parameters.Extract the fitting factors for the corresponding structural parameters in the coupled-mode theory.Construct a theoretical model to realize frequency locking and directional control of SP super-radiation waves based on the analysis of improved coupled mode theory(i-CMT).2.The radiation characteristics of two-dimensional and three-dimensional Skyrmions are studied.Based on the single electron model,with surface current as the implementation method and COMSOL Multiphysics and other software as assistance,the numerical method is used to calculate the angle,frequency,energy flow density,and field distribution of the radiation field generated by different structures under different electron parameters.Then,by using particle simulation software such as CST Studio Suite,the physical mechanism of SP radiation generated by the interaction between the Skyrmions and electron beam is analyzed,and the law of producing adjustable SP radiation by Skyrmions is mastered.The input power and radiation power of SP radiation generated by using the fundamental mode and higher-order mode of the same structure are compared.3.By continuously deforming Skyrmions,the frequency,radiation direction,output power,and efficiency of the radiation wave are observed and compared with those before deformation.