Research On Electromagnetic Wave Generation From Surface Plasmon Polaritons Excited By An Electron Beam

Terahertz(THz) science and technology have been developed quikly. To promote its development, terahertz radiation source is one of the key problems. In this dissertation, the THz radiation from surface plamson polartitons(SPPs) excited by uniformly moving electron beam is studied, and we demonstrate that it is a promising way to develop new THz radiation sources by the method of combining the photonics and electronics. And some new physical mechanism and physical phenomena are revealed in this work.The main achievements are as follows:1. The coherent and tunable THz radiation from graphene SPPs excited by an electron beam is proposed and explored. In graphene based dielectric grating structure, the SPPs excited by a uniformly moving electron beam can be transformed into radiation waves through the diffraction of grating. SPPs significantly improve the radiation power density, it can be as high as 103 W/cm2. And the radiation frequency can be tuned over the whole THz frequencies by adjusting the electron beam velocity and the chemical potential of graphene layer. Therefore, based on this physical mechnism, the room temperature, tunable, coherent and intense THz radiation sources to cover the whole THz band can be developed. From the point of view of practical application, we point out that the dielectric grating deformation due to the manufacture process brings the huge influence on radiation characteristics.2. The coherent and tunable THz radiation from graphene SPPs excited by cyclotron electron beam(CEB) is proposed and investigated. Due to the natural periodicity of 2π of the circular cylindrical graphene structure, SPPs dispersion can cross the light line of dielectric, making transformation of SPPs into radiation immediately possible. The radiation power density reaches 105 W/cm2, which is two or three orders higher than that of radiation from linear electron beam excited graphene based grating structure. And the radiation frequency can be tuned over the whole THz frequencies by adjusting the electron beam velocity, the chemical potential of graphene layer and parameters of the structure. Therefore, this mechanism opens a promising way for developing room temperature, tunable, coherent and intense THz radiation sources to cover the whole THz band.3. The electromagnetic radiation from SPPs in a metal film with periodical arrary loading structure is proposed and explored. The SPPs, excited by a uniformly moving electron beam in the metal film, can be transformed into radiation wave through the diffraction of periodical array. The radiation is also room temperature, tunable, coherent and with high power. We studied three kinds of periodical array structure including prefect conductor, dielectric and two dimensional metal periodical array structure in detail, they have different features, and some physical phenomena are analyzed, such as radiation field interference and mode coupling, etc.4. The Cherenkov radiation via SPPs excitation by an electron beam in a layered metal-dielectric structure is proposed and explored. In dielectric film-metal film-dielectric medium based structure, the SPPs are excited by a uniformly moving electrom bean, when the Cherenkov condition is satisfied, SPPs can be transformed into radiation wave in the medium. Meanwhile, the dielectric film can effectively manipulate the dispersion property of SPPs, the required exciting electron beam energy for generation of light radiation from visible to ultraviolet frequency regime is dramatically lowered In addition, the radiation power density is improved several times due to stronger confinement of SPPs on the metal film.