Abstract
The subject of the thesis is the modelling, design, fabrication and characterisation of passive silicon photonic devices for near (NIR) and mid-infrared (MIR) applications. The NIR devices have been investigated with the aim to produce low temperature sensitive devices for optical interconnects, whilst the results obtained at MIR wavelengths promise great potential for a variety of applications such as sensing and biomedicine. Silicon photonics offers very promising prospects for meeting ever-increasing demands on data speed and bandwidth. Temperature sensitivity of resonant photonic devices is an important issue in the development of ultralow power optical interconnects. This research project reports on the design, fabrication, and characterisation of a low temperature sensitive strip silicon-on-insulator (SOI) racetrack resonators. A resonant wavelength shift of 0.2 pm/K at a 1550 nm wavelength is measured using polymer cladding. The influence of various parameters has been examined achieving a very good agreement with theoretical model. A significant reduction of waveguide propagation losses, improved racetrack resonator Q-value, and higher extinction ratio are obtained after overlaying the silicon waveguides with a polymer cladding. On the other side, MIR silicon photonics is gathering pace, driven mainly by the lure of possible applications such as sensing, free-space communications, thermal imaging and biomedicine. However, the field is still in its infancy and the first serious challenge is to find suitable material platforms for the MIR. The thesis reports experimental results for passive devices based on different material platforms such as SOI, silicon-on-sapphire and silicon-on-porous silicon. It is demonstrated that SOI is useful material for integrated group IV photonics in the 3-4 μm wavelength range, where propagation losses of less than 1 dB/cm have been obtained. The design rules for single-mode and zero-birefringent SOI rib waveguides using stress engineering are also presented. Optical splitters and racetrack resonators based on SOI strip waveguides have been characterised in the 3.7-3.9 μm wavelength range.