Thesis Format
Integrated Article
Degree
Doctor of Philosophy
Program
Electrical and Computer Engineering
Supervisor
Sabarinathan, Jayshri
Abstract
Silicon photonics, despite its rapid advancement and competitive edge in various high-performance applications, faces inherent challenges for integrating nonlinear components caused by two-photon absorption (TPA) and inefficient phase modulation mechanisms. These limitations restrict its broader application in large scale systems like quantum computing, optical switching, and phased arrays, where high-speed, efficient, and small components are needed. This thesis explores the use of photonic crystal edge defects to help address this using optomechanical coupling. It focuses on two primary applications: the generation of an optical frequency comb and the demonstration of a scalable phase tuner. Optomechanical coupling (OMC) offers a promising avenue to overcome the challenges mentioned above. In the strong coupling regime, OMC can facilitate the generation of optical frequency combs with MHz line spacing, a phenomenon that holds significant potential for applications in high-resolution spectroscopy, precision metrology, and RF photonics. However, demonstrating these combs has been challenging due to stringent low-loss requirements. Photonic crystal edge defects are a promising platform offering strong OMC and the potential to harness other nonlinear effects. This thesis demonstrates an optomechanical frequency comb with 33 MHz spacing. The comb was observed for a photon-phonon cooperativity, the ratio of coupling strength over system loss, of 0.088 which is to the author's knowledge the lowest reported to date. In the weak coupling regime, optomechanical phase tuners present an opportunity by providing compact, low-power alternatives to existing the phase tuning methods of thermo-optic and free-carrier dispersion. These approaches are often limited by speed, power consumption, or scalability. A novel, compact optomechanical phase tuner enhanced by a slow light edge defect waveguide was developed in this work. Measurements demonstrated a $V_{\pi}$ phase shift down to 0.75 V while maintaining a large, 200 nm feature size. In addition to the above two applications, this thesis addresses the practical challenges of designing and fabricating optomechanical silicon photonic devices. Particularly, fabrication challenges when integrating electrical components into optomechanical devices and the modelling challenges of fluid damping in dynamically driven devices with nanoscale features. The research results demonstrate the viability of photonic crystal edge defects for both optomechanical frequency comb generation and phase tuning, marking a significant step forward in the commercial scalability of silicon photonics for advanced applications.
Summary for Lay Audience
This thesis focuses on making advances in integrated silicon photonics, a technology used in applications like quantum computing and optical communication. Silicon photonics involves using light to perform various functions traditionally done by electronics, offering faster speeds and more efficiency. However, some technical challenges have limited its commercial use, especially in creating certain devices like frequency combs and phase tuners, which are crucial for advanced systems. The research explores a potential solution called optomechanical coupling (OMC), where light interacts with mechanical motion to perform these tasks. The study specifically looks at a type of structure called a photonic crystal edge defect, which shows promise by having strong OMC. One key focus is on generating optical frequency combs, which are like precise rulers that can be useful in high-resolution measurements, precision instruments, or creating clocks. The research demonstrates that using these edge defects can help create these combs more effectively, potentially leading to better performance in practical applications. A second focus is on developing a new type of phase tuner, which is a device that controls the phase of light in a photonic circuit. The new design uses edge defects to enhance sensitivity, making it operable at low voltage and easier to fabricate. This makes it more suitable for large-scale applications. Overall, this work shows that photonic crystal edge defects could play a vital role in advancing integrated silicon photonics, helping to overcome existing challenges and paving the way for more widespread commercial use in cutting-edge technologies.
Recommended Citation
Poulsen, Brett D., "Optomechanical Coupling in Suspended Photonic Crystal Edge Defect Devices" (2024). Electronic Thesis and Dissertation Repository. 10602.
https://ir.lib.uwo.ca/etd/10602
