Integrated silicon optomechanical system and its applications

Abstract

Optomechanics studies the interaction between the optical force and mechanical objects, and has led to intensive developments in ultra-sensitive measurements, coherent quantum control, optical tweezers, etc. Silicon photonics is a material platform from which Photonics Integrated Circuits can be made, and provide a perfect solution for minimising optical systems. This thesis studies the integration of optomechanics and silicon photonics—integrated silicon optomechanics, and explores its applications in distributed fibre optical sensing (DFOS) and optical trapping. A novel 1.5 µm thick Silicon on Insulator (SOI) platform is also demonstrated, which is advantageous to the two applications compared to the widely-used thin SOI platform.
Firstly, this thesis proposes to use the integrated cavity optomechanical system to generate optical probe signals for DFOS. The proposed application is based on optomechanical oscillation (OMO), through which optical pulse trains (OPT) and sweepingwavelength optical signals (SWOS) for the DFOS application can be generated. Comprehensive analyses on the OMO threshold and oscillation characteristics are conducted, and the extinction ratio (ER), duty cycle (DC) of the OPT and the sweeping range of the SWOS are derived. Examples of utilising OMO-based OPT and SWOS for DFOS applications are then demonstrated. The proposed OMO-based OPT generator and OMO-Based SWOS generator do not rely on external RF sources and optical modulators and can be fully integrated with silicon photonics platform. They thus provide unconventional methods to reshape the optical source generation in DFOS.
Secondly, this thesis presents the design, optimisation and scaling effect of a dualwaveguide optical trap on a SOI platform by comprehensive numerical simulations in Lumerical FDTD Solutions. The simulations demonstrate that the waveguide thickness is a crucial parameter in designing a dual waveguide optical trap. It was found the optimal waveguide thickness generally increases with the gap distance, accompanied by a periodic feature. The optimal waveguide thickness and gap distance display clear scaling effects over the optical wavelength. This thesis also proposes to use the OMO process to load micro/nano-particles. The OMO process can break the adhesive connection between the micro/nano-particles and the container’s surface. The works above not only pave the way for the design and optimisation of dual-waveguide optical trappings for various applications, but also lays the foundation of a fully on-chip optical trapping system working on vacuum or air. Lastly, this thesis experimentally demonstrated a novel 1.5 µm thick SOI platform for integrated optomechanics, rather than the widely-used thin SOI with a top silicon layer less than 300 nm. For both the above two applications, thick SOI shows its advantages. Thick SOI is suitable for fabricating low-frequency mechanical resonators, which are necessary for long-distance DFOS applications. Thick SOI is also essential for dualwaveguide optical trapping with a larger gap distance. In addition, the 1.5 µm thick SOI has high power handling capability, low propagation loss, large mode size, and comparatively small bend radius. Individual integrated silicon optomechanical components based on 1.5 µm SOI platform are designed, fabricated, and measured, including waveguides, grating couplers, MMIs, Bragg gratings, optical microresonators and mechanical resonators. The measurement results show that all the individual photonics components function well. These works lay a solid foundation for the full integration of a silicon optomechanical system in the future.

More information

Identifiers

ORCID for Jize Yan: orcid.org/0000-0002-2886-2847

Catalogue record

Export record