Subwavelength Effects Near A Dielectric Microcylinder Illuminated By A Diffraction-Free Beam

Generation of a photonic nanojet with a slightly subwavelength waist at the back side of a dielectric microsphere or microcylinder impinged by a plane wave has recently shown that the near-field effects may hold not only inside the dielectric microparticle, but also outside it. In this paper we explain how to drastically increase the external near-field effect. For it one has to replace a plane wave or a Gaussian beam by the fully symmetric diffraction-free beam. In this case we observe a deeply subwavelength focusing of the incident beam near the rear edge of the microcylinder. This effect is accompanied by a very strong enhancement of the local electric intensity. Microcylinders with slightly different parameters grant the significant enhancement of the intensity on the whole cylinder surface. These implications of the resonant scattering result from the destructive interference of the propagating spatial harmonics which vanish at the back side of the cylinder in favor of the evanescent ones.