Research on the localized lightfield features of metallic nano-cone-tip optical antenna via investigating near-field lightwave and correlated net-charge distribution.

In this paper, the near-field lightwave characteristics of an arrayed silicon nano-cone-tip optical antenna (NOA) covered by a common metal film, which can be viewed as a featured quasi quantum dot (QD), are carefully investigated. A dipole net-charge distribution closely correlated with the surface lightwaves excited over the antennas by incident lasers with a central wavelength of 633 nm, is clearly observed. An obvious Coulomb-like blockade from the apex apparently influencing the net-charge converging over the surface of NOA, is verified, which can also be predicted by the simulations according to surface standing waves across the apex node. The antinodes of the surface net-charge instantaneous distribution are already pushed away from the normal location owing to the apex Coulomb-like blockade, so as to present a distorted waveform different from traditional standing wave modes. The tip proximity effect leading to a relatively weak net-charge converging over surrounding planar facet and adjacent NOAs, is also discovered.