Overlapping Double-Hole Nanostructure in a Metal Film for Localized Field Enhancement

We propose a nanostructure consisting of an array of overlapping circular holes in a metal film that allows for eight orders of magnitude increased energy density with respect to the conventional diffraction limit. The field enhancement is achieved by combining two effects: focusing in the double-hole structure and the resonance of the array configuration. We study the dependence of the field enhancement on the nanostructure design by using a finite-difference time-domain method and finite-difference mode analysis. The proposed nanostructure design is amenable to focused ion beam milling fabrication, and preliminary structures are shown