Theoretical investigation of optical fibre surface plasmon resonance palladium-based hydrogen sensors /

Abstract

This thesis is an investigation into the operation and optimization of a series of optical fibre surface plasmon resonance (OFSPR) based hydrogen sensors. All devices we investigate are based on a multimode optical fibre that employs a multilayer stack sensing structure coated on the core of the cladding-stripped fibre. For the first time, we investigate the use of a PdY alloy as the H2 sensitive layer in an OFSPR sensor. The alloying of Pd with Y significantly improves durability and permeability. We show that the sensor operates at a level comparable to a pure Pd sensor. We investigate the influence that the thickness of each multilayer component has on sensor performance, and demonstrate a series of optimal sensing configurations that maximize sensor performance for a range of incident light wavelengths. Next, we investigate the operation of a nanocomposite based multilayer structure consisting of Pd nanoparticles embedded in a SiO2 dielectric matrix. We investigate the influence that multilayer component thicknesses, and nanocomposite volume fraction have on performance, and compare operation to an individual multilayer based device. We investigated the operation of a dual-channel sensor by including additional channels along the fibre core. We determined the influence that the thickness of each multilayer component has on the performance of both channels, propose a specific optimal sensor, and demonstrate the operation of additional multi-channel configurations. Lastly, we demonstrate the first evidence of surface plasmon and waveguide mode resonance stimulated at equal wavelengths, using a single multilayer sensing configuration. We characterized the origin of each resonance mode. We demonstrate a drastic improvement in sensor figure of merit compared to that determined using the widely referenced optimal OFSPR sensing configuration. This improvement is attributed to the co-operation between the SPR & TE resonance modes.