Plasmonic nanoantennae fabricated by focused Ion beam milling

We show a novel approach to fabricate plasmonic nanoantennae based on a maskless focused ion beam nanoring patterning process. Antenna nanoarrays with desired outlines are achieved by precisely controlling the geometric parameters during the milling process. Various nanoantenna designs of bow-tie, nanoclusters (pentamers), and ellipsoid shaped satellites surrounded particle lattices are realized. The whole fabrication method is programmable and monolithic since only a one-step milling process is involved. The optical properties are experimentally characterized. Such nanoantennae may find extensive applications in chemical/bio-sensing due to remarkably enhanced near field intensity at the plasmon resonance.