Optical Range Diffraction Radiation of Electron Beam in the Presence of Twin Circular Dielectric Nanowires

Abstract

We study the diffraction radiation that occurs if a modulated beam of electrons flows near a pair of identical dielectric nanowire scatterers, in the visible wavelength range. The electromagnetic field of such a two-dimensional beam has the shape of the surface wave propagating along its trajectory. This wave induces the polarization and surface currents on the nearby obstacles and hence a radiation occurs even if the beam does not touch the obstacle. Here, a pair of dielectric nanowires behaves as an optically coupled open resonator, thanks to which the diffraction radiation is enhanced near the wavelengths of the natural modes. For the pair of twin wires, these modes are so-called supermodes built on the modes of each wire, with account of two-fold symmetry of the pair. We compute spectral characteristics of this resonator, visualize the far field patterns, and analyze their dependence on electron beam parameters.