High-precision acoustic and inertial sensors in interferometric silicon micro-structures
Abstract/Contents
- Abstract
- In recent years, fiber-based optical sensors utilizing a flexible diaphragm microstructure as a mechanical transducer have surpassed conventional electronic MEMS sensors as compact, high-resolution force sensors. They have been implemented as acoustic sensors and accelerometers capable of resolving µPa/√Hz and µg/√Hz over tens of kHz of bandwidth, enabling a wide range of high-performance applications such as long-range inertial navigation, underwater communications, and cellular studies. In particular, state-of-the-art optical MEMS acoustic and acceleration sensors, typically based on Fabry-Perot or phase-front modulation (PFM) interferometers, exhibit a particularly high sensitivity. However, these sensors are difficult to align during assembly, and they have a strong wavelength dependence, which makes it challenging to multiplex them into arrays. They also require active feedback of the wavelength of the laser used to probe them in order to maintain a stable, high sensitivity. This thesis presents the theoretical modeling and experimental characterization of two new generations of PFM sensors that address these issues by self-aligning a fiber with a diaphragm suspended on micrometric springs to form a stable two-wave interferometer. Fabricated on silicon-on-insulator wafers using standard clean-room tools, these sensors are compact and quick to assemble reproducibly, and they exhibit a weak wavelength dependence and no polarization dependence. The first generation of hydrophone has a flat sensitivity extending from 100 Hz to 2 kHz and an average minimum detectable pressure over this region of 74 µPa/√Hz. With a resolution comparable to the noise of quiet ocean environments, these sensors are good contenders for deep-ocean acoustics and seismic monitoring. The second generation of sensors implements a novel self-aligning scheme and demonstrates a reproducible sensitivity spectrum. They exhibit a record low resolution of 215 nPa/√Hz between 40 Hz and 3 kHz, which represents a 10-fold improvement over the previous record reported in the literature. With an equivalent force resolution of 1.5 pN/√Hz, these new sensors are well-positioned for micro-cellular studies. They are in fact sensitive enough to resolve the extremely weak phase noise imparted to the probe light by the thermal noise of the diaphragm structure. When used as accelerometers in a vacuum, their resolution is as low as 160 ng/√Hz over 3 kHz of bandwidth, which satisfies the most stringent requirements for inertial navigation of aircraft.
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2022; ©2022 |
| Publication date | 2022; 2022 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Habib Afshar, Behrad |
|---|---|
| Degree supervisor | Digonnet, Michel J. F |
| Thesis advisor | Digonnet, Michel J. F |
| Thesis advisor | Soh, H. Tom |
| Thesis advisor | Vuckovic, Jelena |
| Degree committee member | Soh, H. Tom |
| Degree committee member | Vuckovic, Jelena |
| Associated with | Stanford University, Department of Electrical Engineering |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Behrad Habib Afshar. |
|---|---|
| Note | Submitted to the Department of Electrical Engineering. |
| Thesis | Thesis Ph.D. Stanford University 2022. |
| Location | https://purl.stanford.edu/kx883kt6770 |
Access conditions
- Copyright
- © 2022 by Behrad Habib Afshar
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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