Generation of microwave and terahertz radiation in a medium of nanoparticles

We investigate the mechanism of radiation generation, whose source are modulated with the variable ( x - υ t ) surface currents in elongated nanoparticles forming a 3D structure. Carbon nanotubes and graphene nanoribbons are considered as elongated nanoparticles. The volume fraction f < < 1 of nanoparticles is considered small (the distance between the centers of nanoparticles is several times greater than their length), thus allowing one to neglect the interaction of two identical nanotubes due to the tunneling effect. Since the velocity of modulated surface currents υ in 3D structure greater than the phase velocity of the light in a medium, then the process is qualitatively similar to the Cherenkov radiation by a system of dipoles that move with the velocity υ . In the case of α -aligned nanofilms based on nanotubes, the radiation wavefront will have a form of a divergent wedge. It is shown that such a structure can generate intense microwave and terahertz radiation and an estimate of the radiation value is made.