Enhanced coherent terahertz Smith-Purcell superradiation excited by two electron-beams.

This paper presents the studies on the enhanced coherent THz Smith-Purcell superradiation excited by two pre-bunched electron beams that pass through the 1-D sub-wavelength holes array. The Smith-Purcell superradiation has been clearly observed. The radiation emitting out from the system has the radiation angle matching the 2nd harmonic frequency component of the pre-bunched electron beams. The results show that the two electron beams can be coupled with each other through the holes array so that the intensity of the radiated field has been enhanced about twice higher than that excited by one electron beam. Consequently superradiation at the frequency of 0.62 THz can be generated with 20A/cm(2) current density of electron beam based on above mechanism. The advantages of low injection current density and 2nd harmonic radiation promise the potential applications in the development of electron-beam driven THz sources.