Tuning of nanofocused vector vortex beam of metallic granary-shaped nanotip with spin-dependent dielectric helical cone

Abstract

We present the combined configuration of dielectric helical cone and metallic granary-shaped nanotip to produce three -dimensional vector vortex nanofocused optical field. The intensity and phase of the electric fields, and Povnting vector of the optical field generated by the combined configuration with linearly polarized illumination are studied with three-dimensional finite difference time-domain method. The localized vector electric field near the apex of the metallic granary-shaped nanotip is strongly depended on the chirality of the dielectric helical cone and the bottom radius of the metallic granary-shaped nanotip. The localized vector electric field is wavelength selective with the maximum intensity enhancement up to 10 times and minimum size of about 900 nm, and the maximum radial electric field rotates 67.0° along z axis. This indicates the vector vortex beam generated by the combined configuration can be applied in nanofabrication, nano-sensing and nano-manipulation.

Visible-broadband Localized Vector Vortex Beam Generator with a Multi-structure-composited Meta-surface

“…For instance, Pancharatnam-Berry phase planar elements [26,27,28,29] and plasmonic vortex lens [30,31,32] realize the function of converting circularly polarized beams into vortex beams. In recent years, combinations of spirals and tapers were proposed for generation of localized vortex beams [6,33,34,35]. In addition, designed artificial structures were reported to convert linearly polarized beams into localized vector vortex beams [35,36].…”

“…In recent years, combinations of spirals and tapers were proposed for generation of localized vortex beams [6,33,34,35]. In addition, designed artificial structures were reported to convert linearly polarized beams into localized vector vortex beams [35,36]. In other words, it was good for nano-miniaturization and integration of optical elements that localized vector vortex beams can be generated without extra polarizers.…”

“…Nevertheless, the proportion of the longitudinal component and the localization of transmitted fields generated by meta-surfaces above is not high enough in theory (<20%) [36], resulting in low-sensitivity and low-precision of particle manipulation, respectively. Besides, most vortex beam generators work only at several certain frequencies [28,29,35]. Therefore, broadband vortex beam generators are significantly useful in wider applications.…”