| Terahertz Science and Technology have been developed rapidly, and the developments of the radiation sources are one of the key researches in this area. In this work, the major study is to explore a new way of merging the electronics and photonics for the new type terahertz sources and devices.The following results have been achieved in this dissertation:1. The possibility of excitation of surface plasmon in conducting metal by electron beam has been discussed. It has been proven that the surface plasmon can be excited and amplified by electron beam just passing above to the surface of metal. This phenomenon may happen if the plasma frequency is just 10-4 of the plasmon frequency of metal.2. The subwavelength holes array has been proposed to explore the interaction of electron beam and mimicking surface plasmon. After theoretical analysis and computer simulation, it has been proven that electron beam can excite the mimicking surface plasmon in the subwavelength holes array and interact with it to produce the terahertz radiation. The advantages of subwavelength holes array structure for the electron beam-wave interaction have been revealed comparing with the traditional slow wave structures. The enhanced transmission phenomenon of subwavelength holes array is utilized to design the two beams interaction sources. The results of computer simulation demonstrate that the sources driven by two beams can produce much more terahertz radiation.3. A novel electromagnetic diffraction radiation phenomenon is discovered. It explores that the physics of electromagnetic diffraction radiation of a subwavelength holes array excited by a set of evanescent waves generated by a line current of electron beam. Actived by a uniformly moving line current, numerous physical phenomena occur such as the diffraction radiation on both sides of the array as well as the electromagnetic penetration below the cut-off through the holes. As a result the subwavelength holes array becomes a radiation array. Making use of the integral equation with relevant Green's functions, an analytical theory for such a radiation system is built up. The results of the numerical calculations based on the theory agree well with that obtained from the computer simulation. The relation between the effective surface plasmon wave, electromagnetic penetration of the holes and diffraction radiation has been revealed theoretically. It has been proven that the phenomena involving the electromagnetic penetration/transmission and diffraction radiation in both sides of the array happen simultaneously. A distinct diffraction radiation phenomenon has been discovered and the mechanism has been disclosed. The experimental research has been carried out in the microwave frequency region. Moreover, the integral equations method for the analytical theory of the diffraction radiation and the electromagnetic penetration/transmission of the SHA can also be extended and explored to other interesting phenomena with SHA structure.4. The work also discusses the diffraction radiation in another periodical structure—Photonic Crystal. Theoretical study and computer simulation on the Vavilov-Cherenkov Radiation (VCR) in 1D and 2D photonic crystal are given in the paper. It has been found previously that there are number of interesting and important behaviors for the VCR in a 2D photonic crystal, such as when the electron energy is lower than the threshold the backward VCR may occur, etc. Some new important features of the VCR in photonic crystal, mainly the radiation excited by a train of electron bunches has been observed and the physical mechanism is examined as well. |
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