Propagation properties of plasmonic micro-zone plates with and without fractals

Abstract

Propagation properties of plasmonic micro-zone plates with and without regular fractals are calculated and analyzed. Three types of structures are presented: a plasmonic micro-zone plate with eight zones, a plasmonic micro-zone plate with a single aperture only, and a plasmonic micro-zone plate with a regular fractal (N=3, s=3). Intensity and phase distributions of the electromagnetic field for the three types of plasmonic structures were calculated by means of three-dimensional numerical computational simulation on the basis of a finite-difference and time-domain algorithm. Our computational results demonstrate that the zones play a dominant role for realizing a superfocusing with a spatial resolution beyond the diffraction limit as well as a micron-scale working distance along the propagation direction.