Silicon Photonics Platforms for Sensing and Telecoms

Abstract

This thesis presents a comprehensive study of the design, fabrication and characterisation of a variety of waveguide-based photonic integrated circuits (PICs) derived from the silicon-on-insulator (SOI) platform. Modelling and design optimisation of various PIC components, including grating couplers and tapered waveguide sections and microring resonators, were implemented along with experimental characterisation. Detailed investigation of a graphene oxide integrated MRR (GOMRR) device, for detection of vapour phase Volatile Organic Compounds (VOCs), reveals an improved sensitivity and correspondingly lower limit of detection compared with a standard silicon (control) MRR. Careful analysis of the optical response of the GOMRR to the various VOCs tested, based on the Hill-Langmuir absorption isotherm, also reveals the potential for discrimination (selectivity), which is not the case for the control MRR. This is attributed to a molecular dependent capillary condensation (within the GO interlayers), which determines the degree of cooperative molecular binding. Our analysis reveals that this cooperativity (increased binding affinity) is enhanced for molecules with a polarity that is high relative to their size (kinetic diameter). This result is consistent with the current understanding of the interaction between GO and various molecules (specifically that the GO serves as an effective 'molecular sieve'), suggesting that it may be used as a functional layer in photonic sensing applications, where molecular selectivity is critical. A novel device based on a Directional coupler integrated MRR (DC-MRR) device was also carried out as part of this study and revealed an enhanced spectral sensitivity (> 14000 nm/RIU) and extended FSR (of 223nm), both of which are key to improved sensing devices based on small footprint SOI-based PICs. A detailed study of superluminal (fast) and subluminal (slow) light is also described using a set of coupled MRRs, whereby thermo-optic tuning of one of the rings with respect to the other was employed. This device exhibits a maximum group delay (for the slow light mode) of 16.25ps and an advance (for the fast light mode) of 239.17ps. Comprehensive analytical modelling, combined with FDTD simulations were employed to support the observed experimental characteristics (electromagnetically induced transparency (EIT)- like effects and anti-crossing behaviour in these coupled MRRs of the fabricated devices.

Date of Award	31 Dec 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Matthew Halsall (Supervisor) & Iain Crowe (Supervisor)