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Light emission from electron-beam driven metasurfaces

Light emission from electron-beam driven metasurfaces
Light emission from electron-beam driven metasurfaces
Over the last decade, free electron beams have been extensively used for characterization of nanostructures, particularly the study of plasmonic excitations using cathodo-luminescence and energy loss spectroscopy. A number of novel light sources based on electron-beam driven nano-antennas, -undulators and -gratings have also been demonstrated.

In this thesis I report on new approaches for controlling emission of light generated by electron beams interacting with nanostructured metasurfaces. In particular, I have developed the first holographic free-electron-driven light source in which emission induced by electrons injected into planar holographic pattern is controlled by the patterns design. On the platform of a conventional scanning electron microscope, using plasmonic, semiconductor and dielectric surface-relief holographic metasurface, for the first time I have experimentally demonstrated:
*  Holographic patterns designed to generate highly-collimated radiation at a given wavelength in a prescribed direction. For example, a surface relief hologram only a few tens of square microns in size milled into a plasmonic gold film and driven by 30 keV electrons emits a light beam at 800 nm with divergence of only 2.5º with an efficiency ~10-7 photons/electron. Continuous output beam steering over ±10º in polar and azimuthal directions via nanoscale positional tuning of electron injection point has also been demonstrated.

*  Holographic patterns designed to create a source of radiation with purposely structured complex wavefronts. I have demonstrated plasmonic patterns that upon electron excitation emit light beams with prescribed topological charge, up to 30.

*  A direction-division multiplexed holographic free-electron-driven light source. The source comprises a microscopic array of plasmonic surface-relief holographic domains, each tailored to direct electron-induced light emission at a selected wavelength into a collimated beam in a prescribed direction. Emission direction is switched by µm-scale repositioning of the electron injection point among domains. I show that cross-talk between adjacent and overlapping domains can be as low as -3 dB at a only 2 µm injection point separation, thereby allowing for small arrays (typically ~40 µm across) and rapid switching of the emission direction.

I also conducted computational studies of free-electron driven Smith-Purcell emission from composite gratings containing multiple slits per period, showing that the relative efficiency of resonant modes can be attenuated or enhanced with the addition and removal of narrow slits.

In summary, the nanoscale electron-driven light sources developed in this work offer an unprecedented level of control over the spectral characteristics, divergence, directionality and topological charge of emitted light. They may find application in lab-on-a-chip and sensor technologies, field-emission and surface-conduction electron emission display technologies, optical signal multiplexing, and charged-particle-beam position metrology.
University of Southampton
Clarke, Brendan P.
4c29e0ec-abb3-4bdd-9ba9-54b2654bd249
Clarke, Brendan P.
4c29e0ec-abb3-4bdd-9ba9-54b2654bd249
Zheludev, Nikolai
32fb6af7-97e4-4d11-bca6-805745e40cc6

Clarke, Brendan P. (2018) Light emission from electron-beam driven metasurfaces. University of Southampton, Doctoral Thesis, 133pp.

Record type: Thesis (Doctoral)

Abstract

Over the last decade, free electron beams have been extensively used for characterization of nanostructures, particularly the study of plasmonic excitations using cathodo-luminescence and energy loss spectroscopy. A number of novel light sources based on electron-beam driven nano-antennas, -undulators and -gratings have also been demonstrated.

In this thesis I report on new approaches for controlling emission of light generated by electron beams interacting with nanostructured metasurfaces. In particular, I have developed the first holographic free-electron-driven light source in which emission induced by electrons injected into planar holographic pattern is controlled by the patterns design. On the platform of a conventional scanning electron microscope, using plasmonic, semiconductor and dielectric surface-relief holographic metasurface, for the first time I have experimentally demonstrated:
*  Holographic patterns designed to generate highly-collimated radiation at a given wavelength in a prescribed direction. For example, a surface relief hologram only a few tens of square microns in size milled into a plasmonic gold film and driven by 30 keV electrons emits a light beam at 800 nm with divergence of only 2.5º with an efficiency ~10-7 photons/electron. Continuous output beam steering over ±10º in polar and azimuthal directions via nanoscale positional tuning of electron injection point has also been demonstrated.

*  Holographic patterns designed to create a source of radiation with purposely structured complex wavefronts. I have demonstrated plasmonic patterns that upon electron excitation emit light beams with prescribed topological charge, up to 30.

*  A direction-division multiplexed holographic free-electron-driven light source. The source comprises a microscopic array of plasmonic surface-relief holographic domains, each tailored to direct electron-induced light emission at a selected wavelength into a collimated beam in a prescribed direction. Emission direction is switched by µm-scale repositioning of the electron injection point among domains. I show that cross-talk between adjacent and overlapping domains can be as low as -3 dB at a only 2 µm injection point separation, thereby allowing for small arrays (typically ~40 µm across) and rapid switching of the emission direction.

I also conducted computational studies of free-electron driven Smith-Purcell emission from composite gratings containing multiple slits per period, showing that the relative efficiency of resonant modes can be attenuated or enhanced with the addition and removal of narrow slits.

In summary, the nanoscale electron-driven light sources developed in this work offer an unprecedented level of control over the spectral characteristics, divergence, directionality and topological charge of emitted light. They may find application in lab-on-a-chip and sensor technologies, field-emission and surface-conduction electron emission display technologies, optical signal multiplexing, and charged-particle-beam position metrology.

Text
Final thesis - Version of Record
Available under License University of Southampton Thesis Licence.
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Published date: December 2018

Identifiers

Local EPrints ID: 428648
URI: http://eprints.soton.ac.uk/id/eprint/428648
PURE UUID: bac74982-1abb-4fdb-9215-def4f57f5513
ORCID for Nikolai Zheludev: ORCID iD orcid.org/0000-0002-1013-6636

Catalogue record

Date deposited: 05 Mar 2019 17:30
Last modified: 14 Mar 2019 01:53

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Contributors

Author: Brendan P. Clarke
Thesis advisor: Nikolai Zheludev ORCID iD

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