He, Feng;
(2024)
Photothermally tuned photoacoustic sensing.
Masters thesis (M.Phil), UCL (University College London).
![[thumbnail of Feng__Thesis (Copyright material removed).pdf]](https://discovery.ucl.ac.uk/style/images/fileicons/text.png) |
Text
Feng__Thesis (Copyright material removed).pdf - Other Access restricted to UCL open access staff Download (63MB) |
Abstract
Optical sensors based on interferometry have been widely applied in photoacoustic imaging due to the many advantages in sensitivity, directivity, and bandwidth. However, building an array of these sensors is still an unsolved problem. One of the bottlenecks is the interrogation wavelength. For the sensors with a low Q factor, multiple sensors can share an interrogation wavelength. But for high-sensitivity variants with high Q factor, e.g., plano-concave microresonators evolved from conventional planar Fabry-Perot (FP) sensors, it is not even possible to do so as the fringes of the interference transfer function (ITF) for each sensor do not overlap. The photothermal effect, predominantly due to light absorption, can alter the FP sensors’ thickness, and thus the ITF fringe position, due to thermomechanical deformation. The photothermal effect can possibly be an ideal method to align the ITF fringes and build an FP sensor array. However, applying this technique can be challenging. On the one hand, the precision would be an obvious concern in aligning these ITF fringes as sharp as sub-nm wide. On the other hand, each sensor in the array will require a customised intensity control, i.e., a tunable light intensity attenuator, as well as feedback control, which could significantly increase the cost of building such a sensor array. In this work, it has been found that the light-cavity interaction, which the photothermal effect is based on, itself can actually function as an effective light-intensity attenuator. This method would save the cost of customised intensity attenuators for each sensor in an array. It has also been found that the self-heating effect not only can align the ITF fringes with high precision by active controlling of the interrogation light’s power and wavelength but also can enhance the robustness of the ITF against surrounding’s temperature/pressure fluctuations and thus avoid the costs feedback control. This method can be simultaneously and universally applied to every sensor in an optical sensor array without further hardware modification for any sensor component. The limit and further development of this method have also been discussed.
| Type: | Thesis (Masters) |
|---|---|
| Qualification: | M.Phil |
| Title: | Photothermally tuned photoacoustic sensing |
| 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/). 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. |
| 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 Med Phys and Biomedical Eng |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10190722 |
Loading...
Loading...Loading...Archive Staff Only
 |
View Item |
