Abstract
We demonstrate the generation of far-field propagating optical beams with a desired orbital angular momentum by using a smooth optical-mode transformation between a plasmonic vortex and free-space Laguerre-Gaussian modes. This is obtained by means of an adiabatically tapered gold tip surrounded by a spiral slit. The proposed physical model, backed up by the numerical study, brings about an optimized structure that is fabricated by using a highly reproducible secondary electron lithography technique. Optical measurements of the structure excellently agree with the theoretically predicted far-field distributions. This architecture provides a unique platform for a localized excitation of plasmonic vortices followed by its beaming.
Original language | English |
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Pages (from-to) | 6636-6643 |
Number of pages | 8 |
Journal | Nano Letters |
Volume | 16 |
Issue number | 10 |
DOIs | |
State | Published - 12 Oct 2016 |
Keywords
- Laguerre Gaussian beam
- Plasmonic vortex
- orbital angular momentum
- singular optics
- spin-orbit coupling
All Science Journal Classification (ASJC) codes
- General Chemistry
- Condensed Matter Physics
- Mechanical Engineering
- Bioengineering
- General Materials Science