Figure 2.

Backscattering and ionic current mapping from a plasmonic antenna array. (a) Backscattering intensity map from scanning a focused laser with longitudinal polarization across the plasmonic antenna array. Each of the nanoantennas in this image has a slightly different gap size, leading to varying scattering intensities. The one structure that had a nanopore drilled in the gap is marked with the yellow arrow/dashed circle. (b) Ionic current map to the scan corresponding to panel a. A clear current increase can be observed when the longitudinally polarized laser hit the plasmonic structure with a nanopore in the gap. The structure with a nanopore drilled in the gap is marked with the yellow arrow/dashed circle. (c and d) Backscattering intensities across an array of plasmonic nanoantennas with different gap sizes under longitudinal (c) and transverse (d) polarizations, respectively. Only under longitudinal polarization, we observe backscattering that is strong and sensitive to the gap size of the antenna, while the scattering in transverse excitation is weak and almost invariant to the gap size of the nanostructures.