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Transparent conductive oxide based hybrid nanostructures for electro-optical modulation

Transparent conductive oxide based hybrid nanostructures for electro-optical modulation
Transparent conductive oxide based hybrid nanostructures for electro-optical modulation
In the last decades, plasmonic resonant nanoantennas have created interest in a wide range of research fields that deal with light confinement on the nanoscale. One promising new research branch involves electrically switchable optical properties, which are scaled down to sub-μm size using plasmonic structures. In this thesis, samples with antenna structures whose resonances can be electrically modulated were designed, fabricated and characterised both electrically and optically. A comprehensive analytical study on the interaction of carrier modulation and optical antennas showed that shifts of the resonance wavelength depend on the antenna aspect ratio and material, and are enhanced if the surrounding medium’s permittivity is near zero.
The simulation capabilities of the properties of transparent conductive oxides were successfully utilised to design an ultrathin optical solar reflector that selectively radiates visible and nearinfrared light while strongly absorbing mid-infrared light. The measured solar absorptance was 0.12 and the IR emissivity 0.79. Such selective reflectors can replace currently-used metallised quartz tiles to reduce launch costs of spacecraft. Combining electrical and optical simulation models with nanoscale resolution, a novel modulator structure was designed. By directly electrically addressing nanoantennas, a modulator was enabled to perform in transmission additionally to reflection. Reducing the ITO volume to a gap-filling removed negative impacts of the ITO background, so that the resulting modulator could freely shift the resonance of the antenna. The final structure showed a greatly enhanced amplitude modulation of 45% and a resonance shift of 38nm at 1550nm with an applied electric field of 1Vnm−1.
Fabricated structures showed that the placing of an ITO gap-loading can be achieved by taking into account height alignment errors of current e-beam systems. Experiments on a planar electrical modulator with a TiN-HfO2-ITO stack showed first electro-optical modulation results, which can benefit from the design developed with the simulation model. The promising results obtained in this thesis open a new pathway for electro-plasmonic modulation in a variety of structures such as tunable reflectors and transmitters in free space or on silicon waveguides.
University of Southampton
Riedel, Christoph Alexander
1ba99a96-d018-4c62-b0f0-67eb3d0b8e5e
Riedel, Christoph Alexander
1ba99a96-d018-4c62-b0f0-67eb3d0b8e5e
De Groot, Cornelis
92cd2e02-fcc4-43da-8816-c86f966be90c

Riedel, Christoph Alexander (2018) Transparent conductive oxide based hybrid nanostructures for electro-optical modulation. University of Southampton, Doctoral Thesis, 140pp.

Record type: Thesis (Doctoral)

Abstract

In the last decades, plasmonic resonant nanoantennas have created interest in a wide range of research fields that deal with light confinement on the nanoscale. One promising new research branch involves electrically switchable optical properties, which are scaled down to sub-μm size using plasmonic structures. In this thesis, samples with antenna structures whose resonances can be electrically modulated were designed, fabricated and characterised both electrically and optically. A comprehensive analytical study on the interaction of carrier modulation and optical antennas showed that shifts of the resonance wavelength depend on the antenna aspect ratio and material, and are enhanced if the surrounding medium’s permittivity is near zero.
The simulation capabilities of the properties of transparent conductive oxides were successfully utilised to design an ultrathin optical solar reflector that selectively radiates visible and nearinfrared light while strongly absorbing mid-infrared light. The measured solar absorptance was 0.12 and the IR emissivity 0.79. Such selective reflectors can replace currently-used metallised quartz tiles to reduce launch costs of spacecraft. Combining electrical and optical simulation models with nanoscale resolution, a novel modulator structure was designed. By directly electrically addressing nanoantennas, a modulator was enabled to perform in transmission additionally to reflection. Reducing the ITO volume to a gap-filling removed negative impacts of the ITO background, so that the resulting modulator could freely shift the resonance of the antenna. The final structure showed a greatly enhanced amplitude modulation of 45% and a resonance shift of 38nm at 1550nm with an applied electric field of 1Vnm−1.
Fabricated structures showed that the placing of an ITO gap-loading can be achieved by taking into account height alignment errors of current e-beam systems. Experiments on a planar electrical modulator with a TiN-HfO2-ITO stack showed first electro-optical modulation results, which can benefit from the design developed with the simulation model. The promising results obtained in this thesis open a new pathway for electro-plasmonic modulation in a variety of structures such as tunable reflectors and transmitters in free space or on silicon waveguides.

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Published date: March 2018

Identifiers

Local EPrints ID: 420940
URI: http://eprints.soton.ac.uk/id/eprint/420940
PURE UUID: db255dcd-a368-45d0-ac60-821f8b4af085
ORCID for Cornelis De Groot: ORCID iD orcid.org/0000-0002-3850-7101

Catalogue record

Date deposited: 18 May 2018 16:30
Last modified: 16 Mar 2024 03:23

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Contributors

Author: Christoph Alexander Riedel
Thesis advisor: Cornelis De Groot ORCID iD

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