|dc.contributor.advisor||Maier, Doctor Robert R.J.||
|dc.contributor.advisor||Barton, Doctor James S.||
|dc.contributor.author||Carter, Richard Mark||
|dc.description.abstract||The use of palladium coated optical fibres containing an in-fibre long period grating (LPG)
structure for the sensing of low concentrations of hydrogen has been investigated. Previous
proof of principle experiments were refined and extended, demonstrating sensitivities of up to
60 pm for 1% hydrogen at an operating temperature of 70°C.
Characterisation of the Pd deposition technique (RF sputter coating) including XPS and SEM
analysis to investigate surface roughness and contamination were carried out and are
discussed. These measurements were prompted by the need to characterise and eliminate
sensor drift associated with delamination of the sensor layer.
Particular care was taken to characterise the optical properties of Pd thin films, both in the
presence of hydrogen and without, through ellipsometry and surface plasmon resonance,
since values gained from the literature showed wide variations. The results presented in this
thesis differ from published Pd refractive indices but are specific for the conditions used in
Techniques to directly measure the refractive index profile within the core of an LPG were
investigated and a possible solution is presented.
Theoretical models to calculate the transmission spectrum of a LPG, both with and without a
Pd layer are presented, discussed and the implications due to the poor characterisation of the
LPG are considered.
The potential use of higher order double cladding modes (with up to 20 times the sensitivity
of the lower mode orders) as a sensing regime is investigated and the practical limitations
|dc.publisher||Engineering and Physical Sciences||en_US
|dc.rights||All items in ROS are protected by the Creative Commons copyright license (http://creativecommons.org/licenses/by-nc-nd/2.5/scotland/), with some rights reserved.||
|dc.title||Hydrogen sensing using palladium coated long period gratings||en_US