Three-dimensional winged nanocone optical antennas

Optical antennas convert propagating far-field radiation into localized near-fields [1]. Perhaps the simplest optical antenna is a sharp metal tip, which is commonly utilized in near-field microscopy and spectroscopy [1,2]. Usually, the coupling of far-field light to the near-field requires either a field polarized along the tip axis (longitudinal field) [2] or a surface grating on the tip [3]. Here, we demonstrate that efficient transformation of incident far-field radiation to localized energy at the cone apex can be achieved using nanocones with wings oriented perpendicular to the tip axis [4].