On a tunable free-electron terahertz radiation source

We propose a tunable free-electron terahertz diffraction radiation source making use of the special kind mechanism of diffraction radiation excited by electron beam coupling with the guided modes in a periodic structure [1,2]. The detailed theoretical investigation and digital simulation confirm the characteristics of the source. The terahertz diffraction radiation sources working around 1THz are proposed. Several promising ways of enhancing the radiation power and efficiency are also presented. Specially, the coherent diffraction radiation excited by pre-bunched electron beam is discussed theoretically and numerically. This mechanism of diffraction radiation may open a good opportunity to the vacuum electronic and bring attractive prospects to develop compact and tunable radiation sources in THz and higher frequency regime.