Fano resonances and topological optics: an interplay of far- and near-field interference phenomena

Fano resonances and optical vortices originate from two types of interference phenomena. Usually, these effects are considered to be completely independent, and in many cases Fano resonances are observed without any link to vortices, as well as vortices with a singular phase structure that are not accompanied by Fano resonances. However, this situation changes dramatically when we study light scattering at the nanoscale. In this paper, we demonstrate that Fano resonances observed for light scattering by nanoparticles are accompanied by the singular phase effects usually associated with singular optics, and we introduce and describe optical vortices with characteristic core sizes well below the diffraction limit.