Subwavelength effects near a dielectric microcylinder illuminated by a diffraction-free beam

Abstract: Generation of a photonic nanojet by a linearly polarized wave beam or a plane wave impinging a dielectric microcylinder implies partial conversion of the propagating waves into the evanescent ones. This conversion is manifested in nanojet waist of subwavelength effective width. However, this known near-field effect is relatively weak. We theoretically show that the incidence of a wave beam formed by two plane waves enables much stronger near-field effects: a deeply subwavelength focusing of the incident beam and a strong enhancement of the electric field on the whole cylinder surface and near it. The domination of the evanescent waves in the vicinity of the cylinder results from the destructive interference of the propagating spatial harmonics of the scattered field dictated by the incident wave beam.