Optical Resonances of Photonic Molecule of Twin High Refractive Index Dielectric Nanowires Excited by Modulated Electron Beam

This work studies the optical diffraction radiation due to a modulated electron sheet beam moving between two identical dielectric nanowires, which form a photonic molecule. The electromagnetic field of such a beam induces the polarization and surface currents on the wires that radiate into the host medium. The corresponding scattering problem is treated with the aid of the azimuth Fourier expansions in local coordinates of each wire and the addition theorems for the cylindrical functions. The final matrix equation, which has mathematically guaranteed convergence, is applied to obtain spectral characteristics of diffraction radiation and visualize the field patterns. Photonic molecule of dielectric nanowires is an optical open resonator; therefore, the diffraction radiation displays the peaks on its natural mode wavelengths. Some of them appear only if the beam trajectory is shifted from symmetric position. This effect can be useful in the design of optical-range beam position monitors.