The ultimate departure from geometrical optics: vortex optical field around plasmonic nanoparticle

Here we report on the discovery of an extreme deviation from geo'metrical optics: light interacting with a metallic nanoparticle, in the proximity of its plasmon resonance, follows curly trajectories with curvatures on a subwavelength scale, creating nanoscale optical vortices. We discuss how the appearance of these vortex structures is related to resonant increases in the absorption and scattering cross-sections of the nano-objects and weather the vortex structure could provide a natural feedback mechanism, thus creating a nano-scale analog of an optical resonator