The University of Southampton
University of Southampton Institutional Repository

Free-electron-driven nanoscale light sources: from Hertzian antennas to metamaterials

Free-electron-driven nanoscale light sources: from Hertzian antennas to metamaterials
Free-electron-driven nanoscale light sources: from Hertzian antennas to metamaterials
This thesis reports on the development of new types of nanoscale optical light sources driven by free-electrons and on the investigation of the underpinning physical phenomena. It is focused on three types of nanoscale light sources with increasing degree of complexity: a nanoscale antenna, an undulator-based tuneable nanoscale light source and a metamaterial-based spatially coherent light source. I have demonstrated for the first time that a nanoscale Hertzian antenna can be driven by free-electrons. The studied nano-antennas consisting of pair of gold nano-rods spaced by a gap resemble conventional radio dipole antennas. Nanoantennas, driven by electron beam produce emission in the visible part of the spectrum. I show that these nanoantennas are most efficiently fed in the region of closest proximity between their two elements, in particular, where the light density of states reaches a maximum. I have developed for the first time a tuneable nanoscale light source driven by free-electrons, the light-well. Alike a free-electron laser that exploits magnet-based undulators, the light-well is based on a nanoscale undulator, a cylindrical channel through alternating metal-dielectric nano-layers. A fast electron propagating through the channel emit light at the wavelength linked to the electron energy and the period of the undulator, thus allowing for a continuous tuning of the output radiation. It has been achieved a 200 nm tunability range in the vis-NIR range at wavelengths between 750 and 950 nm with light at the level of 200W/cm2. Furthermore, I have performed a comprehensive numerical analysis of the light-well by modeling a free electron propagating in the undulator which has lead to a deeper understanding of its physical mechanisms. I demonstrate for the first time an electron-beam driven metamaterial light source that converts the kinetic energy of tree-electrons into spatially coherent optical radiation. It is based on a fundamentally new radiation phenomenon: the injection of free electrons into the metamaterial leads to a directed light emission that comes from synchronized plasmonic oscillations of the ensemble of metamolecules, the individual building blocks of the nanostructure. The effect results from the synchronizing interactions between the metamolecules leading to the spectrum narrowing with the increasing number of metamolecules involved. Depending on the type of metamaterial used I observed emission of narrow-divergent radiation in the visible range from 640 to 760 nm. These results - in principle - demonstrate an alternative to the laser, a threshold-free way of generating spatially coherent and spectrally narrow electromagnetic radiation.
University of Southampton
Adamo, Giorgio
90eaf079-f42c-4de9-ad5f-a01685049941
Adamo, Giorgio
90eaf079-f42c-4de9-ad5f-a01685049941
Zheludev, Nikolai
32fb6af7-97e4-4d11-bca6-805745e40cc6
Macdonald, Kevin
76c84116-aad1-4973-b917-7ca63935dba5

Adamo, Giorgio (2011) Free-electron-driven nanoscale light sources: from Hertzian antennas to metamaterials. University of Southampton, Faculty of Physical and Applied Sciences, Doctoral Thesis, 126pp.

Record type: Thesis (Doctoral)

Abstract

This thesis reports on the development of new types of nanoscale optical light sources driven by free-electrons and on the investigation of the underpinning physical phenomena. It is focused on three types of nanoscale light sources with increasing degree of complexity: a nanoscale antenna, an undulator-based tuneable nanoscale light source and a metamaterial-based spatially coherent light source. I have demonstrated for the first time that a nanoscale Hertzian antenna can be driven by free-electrons. The studied nano-antennas consisting of pair of gold nano-rods spaced by a gap resemble conventional radio dipole antennas. Nanoantennas, driven by electron beam produce emission in the visible part of the spectrum. I show that these nanoantennas are most efficiently fed in the region of closest proximity between their two elements, in particular, where the light density of states reaches a maximum. I have developed for the first time a tuneable nanoscale light source driven by free-electrons, the light-well. Alike a free-electron laser that exploits magnet-based undulators, the light-well is based on a nanoscale undulator, a cylindrical channel through alternating metal-dielectric nano-layers. A fast electron propagating through the channel emit light at the wavelength linked to the electron energy and the period of the undulator, thus allowing for a continuous tuning of the output radiation. It has been achieved a 200 nm tunability range in the vis-NIR range at wavelengths between 750 and 950 nm with light at the level of 200W/cm2. Furthermore, I have performed a comprehensive numerical analysis of the light-well by modeling a free electron propagating in the undulator which has lead to a deeper understanding of its physical mechanisms. I demonstrate for the first time an electron-beam driven metamaterial light source that converts the kinetic energy of tree-electrons into spatially coherent optical radiation. It is based on a fundamentally new radiation phenomenon: the injection of free electrons into the metamaterial leads to a directed light emission that comes from synchronized plasmonic oscillations of the ensemble of metamolecules, the individual building blocks of the nanostructure. The effect results from the synchronizing interactions between the metamolecules leading to the spectrum narrowing with the increasing number of metamolecules involved. Depending on the type of metamaterial used I observed emission of narrow-divergent radiation in the visible range from 640 to 760 nm. These results - in principle - demonstrate an alternative to the laser, a threshold-free way of generating spatially coherent and spectrally narrow electromagnetic radiation.

Text
Adamo 2011 thesis 5241 - Version of Record
Available under License University of Southampton Thesis Licence.
Download (4MB)

More information

Published date: October 2011
Organisations: University of Southampton, Optoelectronics Research Centre

Identifiers

Local EPrints ID: 202301
URI: https://eprints.soton.ac.uk/id/eprint/202301
PURE UUID: 982299f1-dd75-4afb-ae9a-15e2b7c82ffd
ORCID for Nikolai Zheludev: ORCID iD orcid.org/0000-0002-1013-6636
ORCID for Kevin Macdonald: ORCID iD orcid.org/0000-0002-3877-2976

Catalogue record

Date deposited: 11 Nov 2011 09:24
Last modified: 28 Aug 2019 00:37

Export record

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of https://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×