“Needle beam:” Beyond-diffraction-limit concentration of field and transmitted power in dielectric waveguide

Abstract

The authors report the “needle beam,” which is an eigenmode of J0-Y0-K0 profile propagating in a purely dielectric three-medium coaxial cylindrical waveguide, whose field and transmitted power are concentrated within the central medium of diameter beyond the diffraction limit. The huge concentration can be achieved for the TE0m and TM0m eigenmodes within a cylindrical hole of nanometer-scale diameter along the waveguide axis. A difference between refractive indices in the hole and neighbor media can considerably enhance the field and the power transmission along the hole.