Fabrication of coaxial plasmonic crystals by focused ion beam milling and electron-beam lithography

Abstract

Plasmonic coaxial apertures are emerging candidates for single layer metamaterials at visible frequencies. Different mechanisms of extraordinary optical transmission can be observed from coaxial nanorings and they can support localized Fabry–Pérot plasmon modes. However, nanoring fabrication is a challenge due to the well-known difficulties of etching metals, especially for ultrasmall features with deep etching. Here, we demonstrate the fabrication of coaxial structures (nanoholes and nanoparticles) using focused ion beam milling and electron-beam lithography followed by argon ion milling, respectively. Coaxial apertures with up to 20:1 aspect ratio have been achieved using focused ion beam lithography. Single layer metamaterials with high fabrication quality are shown, which could find extensive applications in nanofocusing and imaging.