Generation of Coherent terahertz radiation from two-section periodical circular waveguide structure

Recently, generation of terahertz radiation has become one of the most attractive topics in varieties of fields of physics. In the present paper, the two-section periodical circular waveguide excited by electron beam as a terahertz radiation source is investigated. By choosing the suitable parameters of system, the frequency of the propagating wave in second section (diffraction radiation frequency) is twice the frequency of first section (bunching frequency). The results show that with 20 kV beam voltage, the coherent diffraction radiation with frequency close to .036 THz can be generated. Since, the starting beam current density reduces, it is anticipated that this structure form an important part of future THz systems.