Optical ring resonators in silicon-on-insulator.

The aim of this thesis is to report the results of an investigation into the design and fabrication of a polarisation independent optical ring resonator in the silicon-on-insulator material system. By separating the resonator into its fundamental components and investigating each one in terms of its polarisation properties, it is hypothesized that a ring resonator can be constructed that functions as desired regardless of the input polarisation state. Two test chips were therefore fabricated which are based on experiments designed to validate this hypothesis. A polarisation independent ring resonator has been realised on the first designed test chip which has a TE/TM resonance minimum alignment of better than 5pm, a Finesse of ~ 11 for both polarisations, and a calculated Q value of ~95,000. A second test chip was fabricated to quantify improvements to the first test chip. It yielded a resonator with a Finesse of 28 and a Q value of ~170,000. Several other effects critical to the functionality of a polarisation independent resonator were also observed on devices from the second test chip. Polarisation conversion, with values as high as 45%, was observed on deep-etched bent waveguides with a bend radius of 100?m. Evidence of higher order modes as well as coupling outside the defined coupling were observed in the experimental results of a directional coupler experiment. Secondary resonance minima were observed in the resonator devices. It is likely that either higher-order modes or polarisation conversion are the cause. Overall, the results of this work imply that the method of designing a polarisation independent racetrack resonator is valid. However, improvements are required in the accuracy of the modelling tools to properly design a polarisation independent device as well as explain unexpected results such as polarisation conversion. Key Words: Silicon Photonics, Silicon-on-Insulator (SOI), racetrack resonator, ring resonator, directional coupler, rib waveguide, waveguide bend, polarisation independence, polarisation conversion