Marques, Dylan M;
(2022)
Modelling the optical response of Fabry-Perot ultrasound sensors.
Doctoral thesis (Ph.D), UCL (University College London).
Preview |
Text
phd.pdf - Accepted Version Download (30MB) | Preview |
Abstract
Fabry-Perot (FP) etalons with a parylene C cavity are widely used for sensing ultrasound in applications, such as photoacoustic imaging, due to their wide ultrasound sensing bandwidth, small acoustic element size and high sensitivity. Optical models of FP etalons typically predict higher sensitivity than is measured experimentally, suggesting that the sensitivity of parylene C FP etalons is currently sub-optimal. However, the reason why parylene C FP etalons cannot perform as predicted by the models was not previously understood. To understand the factors limiting the sensitivity of parylene C FP etalons, full-wave optical models able to predict the optical beams transmitted and reflected by FP etalons were developed. To simulate the optical system used to readout FP etalons, the FP etalon models were coupled with models of the illumination and detection optics, allowing accurate prediction of experimentally measured transfer functions. Additionally, FP etalon models allowing simulation of non-ideal FP etalons, such as those with non-parallel and rough mirrors, were developed. Modelled predictions were then compared against experimentally measured transfer functions, which required careful characterisation of the experiment. The comparison showed that the non-parallel mirrors can reduce the sensitivity of parylene C FP etalons by 70%, while roughness present in the parylene C FP etalon mirror can reduce its sensitivity by 25%. Thus, the results show that parylene C FP etalons are limited by both their roughness and non-parallelism. The multiple FP etalon models developed in this thesis are available as opensource software. I expect that they will be a valuable tool to design the next generation of high sensitivity parylene C FP etalons. Example applications include optimising the design of FP etalons for sensitivity assuming non-parallelism or rough mirrors, or calculating the beam profile of the illumination beam which maximises sensitivity.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Modelling the optical response of Fabry-Perot ultrasound sensors |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2021. 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 > 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 UCL > Provost and Vice Provost Offices > UCL BEAMS UCL |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10144630 |
Archive Staff Only
 |
View Item |
