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Addressable nanomechanical photonic metamaterials

Addressable nanomechanical photonic metamaterials
Addressable nanomechanical photonic metamaterials
While metamaterials offer engineered static optical properties, future artificial media with dynamic random-access control over shape and position of meta-molecules will provide arbitrary control of light propagation. In this thesis I report:
• The experimental realization of the first addressable nanomechanical photonic metasurfaces allowing selective actuation of individual metamaterial strips in a single spatial dimension. The devices are constructed from individually addressable plasmonic chevron nanowires with a 230 nm × 100 nm cross-section, which consist of gold and silicon nitride. The active structure of the metadevice consists of 15 nanowires each 18 μm long and is fabricated by a combination of electron beam lithography and ion beam milling. It is packaged as a microchip device where the nanowires can be individually actuated by control currents via differential thermal expansion.

• The novel concept and numerical characterization of a realistic metadevice that dynamically controls the optical phase of reflected light with sub-wavelength pixelation in one dimension. Based on nanomembrane technology, it consists of individually moveable metallic nanowire actuators that control the phase of reflected light by modulating the optical path length. The metadevice can provide on-demand optical wavefront shaping functionalities of diffraction gratings, beam splitters, phasegradient metasurfaces, cylindrical mirrors and mirror arrays with variable focal distance and numerical aperture without unwanted diffraction.

• The novel concept and numerical characterization of a spatial intensity modulator with sub-wavelength resolution in one dimension that combines recent advances in reconfigurable nanomembrane metamaterials and coherent all-optical control of metasurfaces. The metadevice uses nanomechanical actuation of metasurface absorber strips placed near a mirror in order to control their interaction with light from perfect absorption to negligible loss, promising a path towards dynamic beam diffraction, light focusing and holography without unwanted diffraction artefacts.

• The experimental demonstration of a reflective light modulator, a dynamic Salisbury screen where modulation of light is achieved by moving a thin metamaterial absorber to control its interaction with the standing wave formed by the incident wave and its reflection on a mirror. Electrostatic actuation of the plasmonic metamaterial absorber’s position leads to a dynamic change of the Salisbury screen’s spectral response and 50% modulation of the reflected light intensity in the near-infrared part of the spectrum. The demonstrated approach can also be used with other metasurfaces to control the changes they impose on the polarization, intensity, phase, spectrum and directional distribution of reflected light.

In summary, dynamic control over optical properties both in time and space through addressable metamaterials enables focusing, diffraction and redirection of light on demand without unwanted diffracted beams present in commercial spatial light modulators. This work paves the way towards optical properties on demand.
University of Southampton
Cencillo Abad, Pablo Manuel
7d5103d0-e4d3-431b-ac53-7a20b2128228
Cencillo Abad, Pablo Manuel
7d5103d0-e4d3-431b-ac53-7a20b2128228
Zheludev, Nikolai
32fb6af7-97e4-4d11-bca6-805745e40cc6

Cencillo Abad, Pablo Manuel (2017) Addressable nanomechanical photonic metamaterials. University of Southampton, Doctoral Thesis, 184pp.

Record type: Thesis (Doctoral)

Abstract

While metamaterials offer engineered static optical properties, future artificial media with dynamic random-access control over shape and position of meta-molecules will provide arbitrary control of light propagation. In this thesis I report:
• The experimental realization of the first addressable nanomechanical photonic metasurfaces allowing selective actuation of individual metamaterial strips in a single spatial dimension. The devices are constructed from individually addressable plasmonic chevron nanowires with a 230 nm × 100 nm cross-section, which consist of gold and silicon nitride. The active structure of the metadevice consists of 15 nanowires each 18 μm long and is fabricated by a combination of electron beam lithography and ion beam milling. It is packaged as a microchip device where the nanowires can be individually actuated by control currents via differential thermal expansion.

• The novel concept and numerical characterization of a realistic metadevice that dynamically controls the optical phase of reflected light with sub-wavelength pixelation in one dimension. Based on nanomembrane technology, it consists of individually moveable metallic nanowire actuators that control the phase of reflected light by modulating the optical path length. The metadevice can provide on-demand optical wavefront shaping functionalities of diffraction gratings, beam splitters, phasegradient metasurfaces, cylindrical mirrors and mirror arrays with variable focal distance and numerical aperture without unwanted diffraction.

• The novel concept and numerical characterization of a spatial intensity modulator with sub-wavelength resolution in one dimension that combines recent advances in reconfigurable nanomembrane metamaterials and coherent all-optical control of metasurfaces. The metadevice uses nanomechanical actuation of metasurface absorber strips placed near a mirror in order to control their interaction with light from perfect absorption to negligible loss, promising a path towards dynamic beam diffraction, light focusing and holography without unwanted diffraction artefacts.

• The experimental demonstration of a reflective light modulator, a dynamic Salisbury screen where modulation of light is achieved by moving a thin metamaterial absorber to control its interaction with the standing wave formed by the incident wave and its reflection on a mirror. Electrostatic actuation of the plasmonic metamaterial absorber’s position leads to a dynamic change of the Salisbury screen’s spectral response and 50% modulation of the reflected light intensity in the near-infrared part of the spectrum. The demonstrated approach can also be used with other metasurfaces to control the changes they impose on the polarization, intensity, phase, spectrum and directional distribution of reflected light.

In summary, dynamic control over optical properties both in time and space through addressable metamaterials enables focusing, diffraction and redirection of light on demand without unwanted diffracted beams present in commercial spatial light modulators. This work paves the way towards optical properties on demand.

Text
Final thesis - Version of Record
Available under License University of Southampton Thesis Licence.
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Published date: September 2017

Identifiers

Local EPrints ID: 416477
URI: https://eprints.soton.ac.uk/id/eprint/416477
PURE UUID: d6555452-465a-42c5-91c8-a56611acccfd
ORCID for Nikolai Zheludev: ORCID iD orcid.org/0000-0002-1013-6636

Catalogue record

Date deposited: 20 Dec 2017 17:30
Last modified: 14 Mar 2019 01:53

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