Spatially and spectrally resolved orbital angular momentum interactions in plasmonic vortex generators

Abstract

Understanding the near-field electromagnetic interactions that produce optical orbital angular momentum (OAM) is crucial for integrating twisted light into nanotechnology. Here, we examine the cathodoluminescence (CL) of plasmonic vortices carrying OAM generated in spiral nanostructures. The nanospiral geometry defines a photonic local density of states that is sampled by the electron probe in a scanning transmission electron microscope (STEM), thus accessing the optical response of the plasmonic vortex with high spatial and spectral resolution. We map the full spectral dispersion of the plasmonic vortex in spiral structures designed to yield increasing topological charge. Additionally, we fabricate nested nanospirals and demonstrate that OAM from one nanospiral can be coupled to the nested nanospiral, resulting in enhanced luminescence in concentric spirals of like handedness with respect to concentric spirals of opposite handedness. The results illustrate the potential for generating and coupling plasmonic vortices in chiral nanostructures for sensitive detection and manipulation of optical OAM.

Usability of Tilted Plasmon Antenna with Structured Light

“…To realize a plasmonic antenna interacting with light carrying orbital angular momentum, in our case for an LG beam, faces many obstacles [18]; for normal incidence, the antenna size, the beam size, and the working wavelength demand conflicting requirements [19]. To work with larger antennas, one needs to work with higher resonances, this is in addition to the diminished properties of the dielectric constant at short wavelengths [20].…”

Broadband Detection of Multiple Spin and Orbital Angular Momenta via Dielectric Metasurface

“…[ 16,17 ] The generated vortex beam can then transmit either in free‐space or vortex fiber, and finally the OAM information is demultiplexed. [ 18 ] OAM demultiplexing is typically realized using plasmonic devices, [ 19–23 ] Dammann vortex gratings, [ 24–26 ] or transformation optical systems. [ 27–30 ] Undoubtedly, these methods provide new routes to detect the input OAM modes, however they introduce other imperfections such as large energy dissipation in plasmonic systems and the inevitable physical distance between the unwrapper and the phase corrector in transformation optical systems.…”

Selective excitation of localized surface plasmons by structured light

“…Up to now, the excitation of plasmon eigenmodes by structured light was examined on a case by case basis using numerical simulations of the absorption and scattering spectra. Structured light beams were used for exciting dark and bright plasmons with a complex distribution of surface charge density in nanooligomers [2,19,20,21,22], gold tetramers surrounded by a gold nanodisk array [23], coupled nano antennas [24], concentric spirals [25], and a plasmonic coaxial nanoring [26]. The case-by-case approach, however, is inherently limited.…”