Wang, Yupei;
(2023)
Theoretical and Computational Studies of Active Topological Graphene Metasurfaces.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
In this thesis, we present theoretical and computational studies of topological valley plasmon transport on graphene metasurfaces, which were further applied to active optically and chemically controllable nanodevices. The presented results and designs may not only provide deeper insights into topological metasurface with novel symmetry-breaking, but also lead to active photonic nanodevices implemented in robust topological systems. Three configurations of graphene metasurfaces created with the required symmetry to possess valley topological plasmonic modes have been developed: i) a single graphene nanohole metasurface, ii) bilayer graphene metasurfaces, and iii) layered graphene metasurfaces. In all cases, the underlying graphene metasurfaces consist of a hexagonal periodic distribution of circular or triangular air-holes. By introducing additional nanoholes in a single graphene metasurface to break its spatial-inversion symmetry, or by horizontally shifting layers of bilayer graphene metasurfaces with a novel mirror symmetry breaking, or by simply rotating triangular holes in multilayer graphene metasurfaces to break their spatial-inversion or mirror symmetries, the symmetry-protected Dirac cones associated to the three configurations are gapped out. As a result, topological valley interface modes emerge inside the nontrivial bandgap, and the light propagation of the corresponding topological modes along the domain-wall interface shows unidirectional features. Taking advantage of the strong Kerr effect and chemically-tunable optical property of graphene, an active optical switch and an efficient approach to transfer power to topological modes are designed by optically tuning the frequency dispersion of graphene metasurfaces via the Kerr effect, and a molecular gas sensor using the fact that Fermi energy of graphene varies upon chemical doping are investigated.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Theoretical and Computational Studies of Active Topological Graphene Metasurfaces |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2023. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| Keywords: | topological photonics, nonlinear optics, valley-Hall transport, Kerr effect |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10162744 |
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