Infrared diffraction radiation from twin circular dielectric rods covered with graphene: plasmon resonances and beam position sensing

This work considers the near-infrared range diffraction radiation (DR) from a modulated beam of particles passing between two identical dielectric circular nanowires covered with graphene. The resistive boundary conditions are set on the zero-thickness graphene covers with the electron conductivity determined from the Kubo formalism. Assuming that the beam velocity is fixed, we use the separation of variables in local coordinates and the addition theorems for cylindrical functions and cast the DR problem to a Fredholm second-kind matrix equation. This allows us to compute both near- and far-field characteristics with controlled accuracy. The analysis reveals that a shift of the beam trajectory from the central-symmetric position enables the excitation of additional resonances on the modes, which remain “dark” otherwise. Ignition of these resonances can be considered as a tool for noninvasive beam position monitoring with microscale devices.