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.
| Original language | English |
|---|---|
| Article number | 33 |
| Journal | Light: Science and Applications |
| Volume | 8 |
| Issue number | 1 |
| DOIs | |
| State | Published - Dec 1 2019 |
Funding
This research was sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy (J.A.H., J.C.I., B.J.L., R.B.D.), and by an appointment to the Oak Ridge National Laboratory Historically Black Colleges and Universities and Minority Education Institutions Summer Faculty Research Program (S.Y.C.). Work was conducted at ORNL’s Center for Nanophase Materials Sciences (CNMS), which is a U.S. Department of Energy Office of Science User Facility (J.A.H., J.C.I.). Additional support was provided by the U.S. Department of Energy grant DE-FG02-09ER46554 and by the McMinn Endowment at Vanderbilt University (J.A.H., S.T.P.), and by the U.S. Department of Energy grant DE-FG02-01ER45916 (R.B.D., R.F.H.). M.A.F. gratefully acknowledges support by NSF award DMR-1747426 and the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) program. Microscopy experiments were performed at Oak Ridge National Laboratory, supported by the Department of Energy Office of Science, Basic Energy Sciences, Materials Science and Engineering Directorate (MFC). The nanospirals were patterned at CNMS, and the authors acknowledge valuable assistance from Jason Fowlkes in the focused ion beam milling.