Structure of optical Cherenkov radiation in a three-dimensional compound medium with carbon nanotubes

We study the optical Cherenkov radiation in a compound three-dimensional (3D) system with a charge moving over a periodic system of parallel carbon nanotubes. To consider a case of bounded single-walled nanotubes, we apply the numerical finite-difference time-domain technique. We found that, because of the broadband radiation of a charge, the spectrum of the optical field in such a nanosystem is determined by the surface plasmon-polariton excitations. Our study of the field energy spectrum as a function of the plasma frequency detects a nonmonotonic double-well dependency within the area of a surface plasmon-polariton resonance. A well-defined peak that indicates a generation of collective excitations in nanotubes by Cherenkov field is registered. (C) 2019 Optical Society of America