Carbon nanotube as a nanoscale Cherenkov--type light emitter - nanoFEL
  A mechanism of stimulated emission of electromagnetic radiation by an electron beam in carbon nanotubes is theoretically considered. Three basic properties of carbon nanotubes, a strong slowing down of surface electromagnetic waves, ballisticity of the electron motion over typical nanotube length, and extremely high electron current density reachable in nanotubes, allow proposing them as candidates for the development of nano-scale Chernekov-type emitters, analogous to traveling wave tube and free electron laser. Dispersion equations of the electron beam instability and the threshold conditions of the stimulated emission have been derived and analyzed, demonstrating realizability of the nanotube-based nanoFEL at realistic parameters of nanotubes and electronic beams. 
K. G. Batrakov, S.A. Maksimenko, P.P. Kuzhir, C. Thomsen