Directional plasmonic excitation by helical nanotips

The phenomenon of coupling between light and surface plasmon polaritons requires specific momentum matching conditions. In the case of a single scattering object on a metallic surface, like a nanoparticle or a nanohole, the coupling between a broadband effect, i.e. scattering, and a discrete one such as surface plasmon excitation, leads to Fano-like resonance line shapes. We study directional plasmonic excitation - via Fano-like resonance by using a chiral nanotip to excite surface plasmon with a strong spin-dependent azimuthal variation.