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Hybrid plasmonic (HP) waveguides, a multi-layer waveguide structure supporting a hybrid mode of surface plasmonics and Si photonics, is a compromise way to integrate plasmonic materials into Si or SOI platforms, which can guide optical waves of sub-wavelength size, and with relative low propagation loss. In this thesis, several HP waveguides and devices are developed for the purposes of optical communications and sensing. The single-slot HP ring resonator sensor with 2.6µm radius can give a quality factor (Q factor) of 1300 at the communication wavelength of 1.5µm with a device sensitivity of 102nm/RIU (refractive index unit). The Mach-Zehnder interferometer (MZI) with a 40µm double-slot HP waveguide has a device sensitivity around 474nm/RIU. The partly open silicon side-coupled double-slot HP ring resonator has a device sensitivity of 687.5nm/RIU, with a Q factor over 1000 after optimization. Further, an all-optical switching HP donut resonator with a photothermal plasmonic absorber is developed, utilizing the thermal expansion effect of silicon to shift the resonant peak of the HP resonator. The active area has a radius of 10µm to match the core size of a single-mode fiber. By applying 10mW power of the driving laser to the absorber, the resonator transmitted power can be changed by 15dB, with an average response time of 16µs. Using the same fabrication flow, and removing the oxide materials using hydrogen fluoride wet etching, a hollow HP waveguide is fabricated for liquid sensing applications. The experimentally demonstrated waveguide sensitivity is about 0.68, which is more than twice that of pure Si waveguide device. Microelectromechanical systems (MEMS) can also be integrated into vertical HP waveguides. By tuning the thickness of the air gap, over 20dB transmitted power change was experimentally demonstrated. This can be used for optical switching applications by either changing the absorption or phase of the HP devices. / <p>QC 20170427</p>

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This thesis presents a resource based approach to model generation for performance characterization and correctness checking of large scale telecommunications networks. A notion called the timed automaton is proposed and then developed to encapsulate behaviours of networking equipment, system control policies and non-deterministic user behaviours. The states of pooled network resources and the behaviours of resource consumers are represented as continually varying geometric patterns; these patterns form part of the data operated upon by the timed automata. Such a representation technique allows for great flexibility regarding the level of abstraction that can be chosen in the modelling of telecommunications systems. None the less, the notion of system functions is proposed to serve as a constraining framework for specifying bounded behaviours and features of telecommunications systems. Operational concepts are developed for the timed automata; these concepts are based on limit preserving relations. Relations over system states represent the evolution of system properties observable at various locations within the network under study. The declarative nature of such permutative state relations provides a direct framework for generating highly expressive models suitable for carrying out optimization experiments. The usefulness of the developed procedure is demonstrated by tackling a large scale case study, in particular the problem of congestion avoidance in networks; it is shown that there can be global coupling among local behaviours within a telecommunications network. The uncovering of such a phenomenon through a function oriented simulation is a contribution to the area of network modelling. The direct and faithful way of deriving performance metrics for loss in networks from resource utilization patterns is also a new contribution to the work area.

Following the privatisation programme of public utilities implemented by the UK government in the 1980s and early 1990s, an interesting debate on the impact of regulation on the cost of equity capital has emerged. While the effects of regulatory announcements have been studied extensively in the USA, there is very little systematic evidence in the UK. This thesis partly redresses this imbalance by analysing the impact of regulatory announcements on the ex-post returns of equity capital and systematic risk of three utility industries in the UK, namely the electricity, telecommunications and water industries. The main objective of this thesis is to test the impact of regulatory announcements that relate to competition, pricing and the quality of services on the return and risk of equity capital. By using an event-study type methodology, the thesis attempts to isolate the effects of regulation from technical and market uncertainties. The methodology normally used in this type of studies is extended to adjust for the well-documented problem in financial time series of volatility clustering and to allow for changes in the systematic risk through time. Overall, the results in the empirical chapters reveal some important issues. While it is clear from the debate in the literature that the cost of capital influences the choice of regulatory parameters, this thesis provides evidence to support the view that regulation in turn alters the cost of equity capital by affecting the ex-post returns and systematic risk of both individual regulated companies and industries. Although the direction and size of these effects of regulation are not always easy to predict, there is evidence to suggest that they may depend crucially on the structure and competitive posture of the industry, as well as technological and market conditions and the parameters of the regulatory system.

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From the examination of the channel characteristics experienced in the mobile radio environment, it is apparent that the development of data transmission based upon non-binary systems as an alternative to commonly used binary methods is long overdue. A poly-signal modem has emerged from such a design consideration which is unconventional by virtue of its use of the time/frequency parameters available. Because of the complication of modelling the mobile channel one poly-signal scheme with particular advantage was chosen for analysis and the final design compared with a conventional binary system both in laboratory simulations, and also by field trials. It has been shown that under multipath fading conditions, the poly-signal modem maintains a probability of error curve which is normally associated with white noise interference, while binary error curves are modified to a simple function. The two error curves diverge resulting in an apparent increasing improvement for the poly-signal system as bit error rate reduces. For a bit error rate of 10-5 a 10 dB signal to noise ratio advantage is achieved with the new modem compared with the binary, when both operate at 600 bits per second. The improvement is a result of the immunity the poly-signal scheme has to time dependent interference.