Local field effect in diffraction radiation from a periodical system of dielectric spheres

We present a theory of diffraction radiation from a two-dimensional system that consists of small spherical particles on a metal substrate. The interaction between a moving charge and single particles is described in the frames of local field theory. The local field effects are proved to lead to a sharp increase of the radiation intensity at certain frequencies, similar to the effect of giant Raman scattering. The case of nanoparticles is explored and it is shown that the possible enhancement of radiation can reach some thousands of times in the THz range. The Smith–Purcell effect is investigated for the case when the system of particles is periodically arranged.