| The rapid development of modern science and technology lead to the growing requirement of radiation sources. The generation of radiation by the combination of electronics and photonics becomes the focus of this research topic. Surface plasmon polaritons(SPPs) is the natural link of electronics and photonics. Therefore, the study of the electron beam excitation of SPPs and the radiation based on the excited SPPs are of great significance. The excitation of metal and graphene SPPs by electron beam and the radiation transformation of the excited SPPs are studied in this dissertation.There are following results:The excitations of SPPs by perpendicularly and parallel moving electron beam are investigated in this dissertation. The results show that the behavior and properties of the excited SPPs strongly depend on the excitation methods. SPPs excited by perpendicular electron beam contain plenty of frequency components, propagate with attenuation, and are always accompanied with transition radiation(TR). However, for parallel excitation,SPPs waves are tunable, coherent, propagating without attenuation and TR does not occur. The further investigations show that SPPs on the metal film can be excited efficiently by the parallel moving electron beam. In general, the SPPs field amplitudes of the symmetrical mode are larger than that of asymmetrical mode in symmetrical film structures; whereas SPPs of asymmetrical mode have larger field amplitudes than that of symmetrical mode in asymmetrical film structures. And the operating frequencies of symmetrical mode SPPs can be tuned in wider frequency range by adjusting the beam energy than that of asymmetrical mode.Two kinds of radiation transformations of the parallel excited SPPs are studied in details. The first one is that the excited SPPs are transfromed into coherent and tunable Cherenkov radation in the dielectric medium with power enhancement. The results show that the radiation power enhancement and the operating frequency greatly depend on the excited SPPs. And the dependences of them in this radiation transformation on the parameters of the structure and the electron beam are also analysed in this dissertation. And more structures based on this transformation mechanism are presented and analyzed. The second one is that the parallel excited SPPs are transformed into radiation waves by the diffraction radiation in periodical structures. The results showthat the operating frequencies of this special diffraction radiation are determined by that of the excited SPPs. Comparing to the traditional diffraction radiation, the power of the transformed radiation is dramatically enhanced, and the operating frequencies can be tuned in a large frequency range by adjusting the beam energy.The excitation of graphene SPPs by electron beam and the terahertz radiation transformed from the parallel excited graphene SPPs are studied in this dissertation. The results show that the graphene SPPs can be efficiently excited by electron beams. The perpendicularly excited graphene SPPs contain plenty of frequency components and propagate with attenuation, whereas the parallel excited graphene SPPs are coherent,their operating frequencies can be tuned by adjusting not only the electron beam energy but also the chemical potential, and they propagate without attenuation. Graphene SPPs can be excited and amplified by the continuous electron beam when the current density is larger than 500 A/cm2. Further investigations show that graphene SPPs excited by parallel electron beam can be transformed into terahertz radiation by periodical structures. The radiation frequency can be tuned by both the beam energy and the graphene chemical potential, and the radiation power is dramatically enhanced comparing to that without graphene sheet loading. Based on this, tunable terahertz radiation sources working in the whole terahertz frequency region at room temperature can be obtained. |
