Abstract
Optical complex fields have attracted increasing interests because of the novel effects and phenomena arising from the spatially inhomogeneous state of polarizations and optical singularities of the light beam. In this work, we propose a spiral blade plasmonic vortex lens (SBPVL) that offers unique opportunities to manipulate these novel fields. The strong interaction between the SBPVL and the optical complex fields enable the synthesis of highly tunable plasmonic vortex. Through theoretical derivations and numerical simulations we demonstrated that the characteristics of the plasmonic vortex are determined by the angular momentum (AM) of the light, and the geometrical topological charge of the SBPVL, which is govern by the nonlinear superposition of the pitch and the number of blade element. In addition, it is also shown that by adjusting the geometric parameters, SBPVL can be utilized to focus and manipulate optical complex field with fractional AM. This miniature plasmonic device may find potential applications in optical trapping, optical data storage and many other related fields.
Highlights
Orbital angular momentums of light are no longer independent physical quantities but are tightly coupled[16]
Where m denotes the number of blade element, r0 is a constant indicating the distance from the geometrical center to the innermost edge of the spiral blade plasmonic vortex lens (SBPVL), mod(mφ,2π ) represents the reminder of the division of mφ by 2π, and Δ φ = 2π/m
We proposed a SBPVL design that is suitable to convert the optical complex field into tailorable plasmonic vortex
Summary
Orbital angular momentums of light are no longer independent physical quantities but are tightly coupled[16] This change depends on the polarization of the incident light and the topology of the medium, the relationship of which can be described by the concept of geometrical phase (or Pancharatnam-Berry phase)[17]. According to the polarization mode match theory, the receiving efficiencies of the optical beams with radial and circular polarizations can be maximized with bull’s eye and spiral Archimedes’ plasmonic lens, respectively[13,21] These plasmonic structures can be used to detect AM of light or generate SPPs vortices[22,23,24]. The optical AM conservation law during the process of SPPs vortex generation is validated as an evidence of the spin-orbit interaction in this plasmonic system
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