Abstract
Manipulation of a vector micro-beam with an optical antenna has significant potentials for nano-optical technology applications including bio-optics, optical fabrication, and quantum information processing. We have designed and demonstrated a central aperture antenna within an Archimedean spiral that extracts the bonding plasmonic field from a surface to produce a new vector focal spot in far-field. The properties of this vector focal field are revealed by confocal microscopy and theoretical simulations. The pattern, polarization and phase of the focal field are determined by the incident light and by the chirality of the Archimedean spiral. For incident light with right-handed circular polarization, the left-handed spiral (one-order chirality) outputs a micro-radially polarized focal field. Our results reveal the relationship between the near-field and far-field distributions of the plasmonic spiral structure, and the structure has the potential to lead to advances in diverse applications such as plasmonic lenses, near-field angular momentum detection, and optical tweezers.
Highlights
Phase generation applications[27,28,29]
The intensity distributions of the surface plasmons (SPs) field generated by the plasmonic Archimedean spiral, which depend on the handedness of the incident circularly polarized light, have been experimentally verified by NSOM in earlier study[24]
Switchable polarizations can be obtained by adjusting the distance in the z-direction; by controlling the angle of incidence, the focal spot position can be scanned in the longitudinal plane to realize dynamic manipulation
Summary
Phase generation applications[27,28,29]. Because SPs decay exponentially with the distance away from the surface, the reported focal field of the PASL is always restricted to within the near field, which limits its practical application. The field distributions in the near and far fields, which are affected by the interactions between the chirality of the Archimedean spiral and the spin angular momentum of the incident light, were analysed.
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