Compact High-power Sub-THz and THz FELs Based on Planar Micro-undulators and Relativistic Electron Beams

Micro-undulators allow reducing the particles energy of electron beams used for operation of short-wavelength (including terahertz) free electron lasers (FELs). Planar micro-undulators with a period of 1–5 mm were recently implemented at IAP RAS. Such planar micro-undulators are compatible with planar waveguides open in transverse (lateral) direction, which provides diffractive mode selectivity. In terahertz frequency band, the feedback and mode selection with respect to both longitudinal and second transverse (directed normally to the plates) co-ordinates can be provided by the advanced Bragg structures based on coupling of the propagating and the quasi-cutoff modes. These structures are realized by applying to the waveguide wall of a corrugation with a period of the wavelength. To feed the FEL with the planar micro-undulator, we suggest to use a ribbon high-current relativistic electron beam. Based on simulations, we demonstrate that such a beam with particles energy less than 1 MeV and current of 1–2 kA is sufficient for providing of 10–15 MW of radiation power at the frequency of 0.5 THz.