UBC Theses and Dissertations
Feasibility of optical gyroscopic sensors in silicon-on-insulator technology Guillén-Torres, Miguel Ángel
In the last decade, silicon photonics has become a strategic technology for the development of telecommunications and sensors. Due to its compatibility with well-developed complementary metal oxide semiconductor (CMOS) fabrication processes, silicon on insulator (SOI) wafers can be processed to create thousands of devices per die in a fast and inexpensive way. Being solid state devices with no movable parts, optical gyroscopes have longer life expectancies and shock resistance compared to micro-electro-mechanical gyroscopes. Thus, the implementation of SOI-based gyroscopes is desirable for large-scale, low-cost production. This thesis presents a study of the feasibility of implementing optical gyroscopes in SOI technology. A comprehensive theoretical study has been carried out to develop a device-level optimization and robustness analysis, showing that the most crucial resonator parameter is the propagation loss, followed by length and coupling. For a given propagation loss, there is an optimal resonator size, beyond which the angular speed resolution is severely degraded. On the system level, the impact of signal-to-noise ratio and insertion loss on the resolution are described. Given that the propagation loss is the most important parameter, strategies were proposed to reduce it as much as possible while still using CMOS-compatible processes. The quality factor, Q was chosen as the figure of merit to be maximized during the design iterations. As a result, the largest Q factors reported to date on SOI, using standard CMOS-compatible processes, were achieved. These Q factors are comparable to, or exceed, those of optical resonators intended for gyroscopic applications that are fabricated in materials such as indium phosphide (InP). Innovative approaches to compensate for fabrication variations are proposed, such as thermally-tuneable coupling and reference rings for differential measurements. Complex mechano-opto-electrical measurement setups were designed and implemented to characterize SOI gyroscopes, both at rest and under rotation. As a result, the Microsystem Integration Platform for Silicon-Photonics (Si-P MIP) was created. This characterization platform is now being commercialized by CMC Microsystems for academic and industrial applications. The main practical and theoretical challenges regarding the implementation of optical ring gyroscopes on SOI have been identified. Schemes to address them and suggestions for future work are proposed.
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