Gosling, Jonathan;
(2024)
Control of levitated nanoparticles for sensing and characterisation.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
This thesis presents a study of the control of levitated nanoparticles and the utilisation for single nanoparticle characterisation and force sensing. This research focused on four areas, levitation of bipyramidal Yb3+ doped YLF nanocrystals, Levitodynamic spectroscopy, electrical feedback cooling with controlled cross-talk, and directional force sensing. Laser refrigeration of levitated Yb3+ doped YLF nanocrystals has been demonstrated previously. However, the Yb3+:YLF nanocrystals lacked consistency in shape. As part of this thesis, the capability for laser refrigeration of colloidally grown Yb3+:YLF nanocrystals was investigated. Whilst no laser refrigeration was measured, the wavelength-dependent heating observed could be used to examine the spectrally dependent absorption of a single levitated nanocrystal. In this thesis, a technique called Levitodynamic spectroscopy was developed to characterise nanoparticle morphology. This technique utilises the librational motion of an asymmetrical nanoparticle when levitated in linearly polarised light. This technique was experimentally verified by two sets of bipyramidal YLF nanocrystals. Levitodynamic spectroscopy can be employed to differentiate between nanocrystals and biological samples, with initial investigations with tobacco mosaic viruses presented. Velocity damping has previously been used to cool the centre of mass motion to the quantum ground state. This technique has been extended to cooling all three translational degrees of freedom. However, as the implementation can induce cross-talk between the mechanical modes, this thesis presents a new method of implementing velocity damping with minimal cross-talk. Directional force resolution is appealing for applications such as dark matter searches where directionality to the interaction is expected. In this thesis, the cross-correlation mechanical spectra were measured for a directional stochastic force. The cross-correlation spectra provide a distinct signature of the directional force without calibration.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Control of levitated nanoparticles for sensing and characterisation |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2024. 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/). |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10192690 |
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| 2. |  Germany | 2 |
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