|Publication No: 810P||Search all ORC publications|
The ultimate departure from geometrical optics: vortex optical field around plasmonic nanoparticle
M.V.Bashevoy*, V.A.Fedotov, N.I.Zheludev
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.
Two different types of vortex have been detected using three-dimensional final element calculations and analytical Mie theory. Outward type vortices first penetrate the particle near its centerline then, on exiting the particle, the flow-lines turn away from the centerline and enter a spiral trajectory. Outward vortices are seen for wavelengths shorter then the plasmon resonance. For wavelengths longer that the plasmon resonance the vortex goes inward: the power-flow lines pass around the sides of the particle before turning towards the centerline and entering the particle to begin their spiral trajectory.
Similar phenomenon has also been found in the microwave part of the spectrum at a planar meta-material structure under resonant conditions corresponding to the so-called 'magnetic mirror' regime.
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.
QEP-17 at Photon06 Manchester, UK 4 - 7 Sep (2006)
Publisher′s URL: Only abstract is available
Southampton ePrint id: 57750
Copyright University of Southampton 2006