Temperature dependent studies of a selection of materials including erbium-doped yttrium aluminum garnet (Er:YAG), zinc nitride nanocrystals(NCs) and manganese-doped cadmium selenide (CdMnSe) NCS have been undertaken in order to determine their fundamental optical properties. The study is based upon the measurement of their photoluminescence (PL) and PL transient decay transient over the temperature range of 300K to 5K. For the Er:YAG samples, two different sample types are studied as a function of erbium concentration that are a fast-cooled (mono-phase) and a slow-cooled (bi-phasic) polycrystalline material. Due to the presence of emission upconversion in these materials the emission dependence on excitation power is also studied. It is found that for high Er concentrations (40-50%) energy transfer upconversion (ETU) occurs that may be of use for assisting population inversion at the 4I11/2 level for the laser 3µm emission. Generally it is confirmed that the single phase and bi-phasic materials possess slightly different optical properties and that the material production must therefore be carefully controlled in order to realize optimized materials for optical applications. Zinc nitride NC materials are studied for the first time with four samples representing a range of NC diameters characterized. These materials were highly susceptible to oxidation which presented a significant challenge in their handling and study. Strong emission was observed across the visible spectral region though the origin of this it was found probably included trap state emission and for the smallest NC samples organic ligand emission. The PL was found to shifting to higher energies as the size of the NC is decreased as expected due to increased quantum confinement and in line with the Brus equation. Two of the samples (8.9nm and 2.7nm diameter NCs) display a temperature dependence of the optical properties in line that seen in other semiconductor NCs such as PbS. The other samples displayed anomalous behavior that could be due to ligand emission (2.5nm NC sample) or higher energy trap states caused by localized oxidation (3.8nm NCs). A study of temperature dependent optical properties of CdMnSe NCs was focused around the role of NC shape and type. Core only, core/shell and dot-in-rod samples were studied and all found to display a blue shift as temperature is reduced from 300K to ~5K of between ~24meV to 58meV. The core only NCs display a different luminescent behavior to that of the core-shell and dot-in-a-rod samples. The PL is related to the recombination of confined excitons within the NC, together with a contribution from what are most probably trap states located at the surface of the NC. In these samples no contribution from the Mn2+ ion is found suggesting that the dopant ions are not fully incorporated into the NC but may reside on the surface.

This thesis describes work on numerical modelling of the 43Ca+ ion in a Paul trap using the optical Bloch equations. This is a challenging system to study, with many states involved in the internal dynamics. A major outcome is the development of a cooling scheme for the 146.09 gauss atomic clock transitions which makes use of a dark resonance. It is much more effective than methods that avoid coherent effects. The scheme is realised in experiment. Complicated fluorescence data is modelled very well, and predictions for the ion's motional temperature show good agreement with measured values. Data and fits for an ion that has been Doppler cooled below the Doppler limit are presented. I describe GLOBES, a set of routines that simulates an arbitrary ion in the presence of an arbitrary system of laser beams using the optical Bloch equations. Techniques used to efficiently calculate the steady state, analyse fluorescence scans and solve time-dependent problems for small and large times are discussed. A new routine SILVER IMPER that leapfrogs over the initial dynamics to model the approach to the steady state is introduced. Doppler cooling in 40Ca+ is analysed and two extensions made to the basic theory. The 'excursion method' of calculation takes account of the non-linear variation with velocity of the scattering rate. The 'dynamic method' allows for the fact that the ion may not be in equilibrium with the incident radiation during its oscillations, a necessity as the timescale of the external motion is of order the characteristic timescale of the internal motion for standard secular frequencies. This 'dynamic effect' is a general property of trapped ion systems and is also observed in a two-state system. A two-variable fluorescence scan taken from a four-laser, five-level system in 40Ca+ is analysed. Techniques to fit large data sets and automatically resolve resonant features are demonstrated. A general treatment of resonant behaviour in three, four and five level pump/probe systems is used to describe the data. This is verified by a second, tailor-made set of scans.

A novel ultrafast direct laser writing (DLW) system using adaptive optics is proposed and demonstrated. This system has the potential to generate high-quality three-dimensional (3D) optical waveguides and components. The experimental setup and procedures for the DLW process are studied, after which various optical waveguides are fabricated in different transparent materials. The resulting waveguides are characterised by the measurement of the near-field laser coupling profiles in combination with optical microscopy techniques. Quantum random number generation (QRNG) and the potential application of the DLW technique in quantum information is also discussed. To completely understand the fabrication procedures for the DLW system, the experimental equipment and effects of different fabrication parameters are studied and analysed. With the use of a liquid-crystal spatial light modulator (SLM) in the DLW system, dynamic control of phase modulation can be provided to correct aberrations adaptively. An SLM can also make the cross-sectional profile of the written waveguides more circular and facilitate the fabrication of more complex 3D structures. Experiments reveal that the shape of the focal spot can be improved dramatically with adaptive optics, resulting in higher-quality optical waveguides. The refractive-index information of the written waveguides and their optical properties are measured using the propagation-mode near-field method (PMNFM). Simulation results and experimental measurements of a commercial single-mode fiber and a waveguide sample are demonstrated and compared. Quantitative phase measurement is also applied via the transport of intensity equation (TIE) to monitor the refractive-index change during fabrication. The propagation losses of the waveguides are measured and discussed. Different optical waveguides are fabricated using DLW in fused silica, potassium dihydrogen phosphate (KDP), and lithium niobate (LiNbO3) crystals. Different materials have different characteristics and properties, requiring different fabrication parameters and resulting in waveguides exhibiting different properties. Waveguides at various depths are demonstrated both with and without effects of adaptive optics. Experimental results indicate great improvements in the quality of the written waveguides after aberration correction. With an understanding of the optical properties of the straight waveguides using the characterisation methods, modelling and fabrication of bend waveguides and y-splitters are presented and studied. A high-speed QRNG system is also demonstrated in this thesis, with potential implementation using the DLW technique for a more compact and stable system. Finally, the possibility of the DLW fabrication of complex 3D optical components and their applications are discussed for future work.

In this thesis I use sub-pixel optical matching, Interferometric Synthetic Aperture Radar (InSAR), and Light Detection and Ranging (lidar) spatial geodetic observations to produce reliable 3D displacement fields caused by co-seismic events and reliable earthquake source models with slip distribution on fault planes. I produce horizontal displacement maps for the 2005 Dabbahu segment, Afar using SPOT4 satellite images. By combining InSAR descending data and range offsets with optical sub-pixel I produced a vertical displacement map of the event. I attempted to perform the inversion of the dataset obtained by sub-pixel matching but I found that datasets are not well suited for the typical numerical inversion, and I fit data with direct dislocation modelling instead. I identify biases and errors that arise from optical sub-pixel matching of satellite images using many horizontal datasets constructed using SPOT5 images for the El Mayor-Cucapah earthquake. I develop algorithms for removal of some of these biases from horizontal displacement maps. Using sub-pixel matching I asses the quality of several DEMs available to me for study of the El Mayor-Cucapah earthquake. I developed a novel technique for producing vertical displacement maps caused by an earthquake by combining archived pre-event satellite images with post event acquired lidar. I use this technique to produce a vertical displacement map of the El Mayor-Cucapah earthquake. I produce a source model of the El Mayor-Cucapah earthquake by inverting InSAR datasets using the method. After attempts to do joint inversion of InSAR and optical sub-pixel matching I developed the code to use Bayesian inversion instead, because its advantages when it comes to joint modelling of datasets. I sucessfully invert four InSAR datasets on seven fault planes using the Bayesian approach. I found that the results of the Bayesian inversion are very similar to the results of the optimization inversion.

The work described in this thesis has been funded by the “Engineering and Physical Sciences Research Council’s Centre for Innovative Manufacturing in Photonics” and has been part of the work undertaken by the “Non-Silica Glasses and Related Fibre Technology” work package, within the “Novel Glass and Fibre” group at the Optoelectronics Research Centre. Original contributions to the field include the development of a novel fibre drawing tower, which has allowed over three hundred fibre draws to be accomplished, resulting in composite metal-glass fibre and infrared transmitting fibre manufacturing processes being established. Most significantly, a refined fibre drawing procedure to produce up to 50 km of continuous glass-encapsulated microwire has been created. Fibre has been fabricated with an outer diameter of around 23 μm and inner diameter of around 4 μm, featuring standard deviations of just 2.2 and 0.8 μm for outer and inner diameters respectively, over kilometres of length. A large portion of the work reported in this thesis has been in collaboration with industrial and academic partners, including Rolls Royce, Shell, National Physical Laboratory, Nanyang Technological University, Laboratory of Ultrafast Spectrometry and others. Characterisation of optical materials has founded relationships with many partners including the University of Oxford and SPI Lasers Ltd. Analysis has been carried out for many groups within the Optoelectronics Research Centre, including the Photovoltaic, Compound Glass, Silica Fibre Fabrication and Integrated Photonics groups. Other academic units at the University of Southampton including the ‘Electronics and Computer Science’, Chemistry and ‘Engineering and the Environment’ departments have also had valuable material characterisation performed with the use of the facilities described in this work. Impurity analysis of optical glasses and raw materials has established a relationship with Northern Analytical Laboratory Inc., who has provided continued analysis for the advancing glass melting facility mentioned in this thesis.

In this thesis I describe my work on the development and fabrication of fibres for beam delivery and generation. In all cases it is assumed the fibres will be suitable for high power applications. I describe the challenges of fabrication and refinements to existing techniques needed to produce and characterise the diverse fibres. Two jacketed air clad (JAC) fibres with square cores are developed. One is a passive delivery fibre that has capacity to capture a larger beam parameter product than other research and commercial fibres and was designed to deliver the output from a 1800 W diode source. The second jacketed air clad fibre has an inner core doped with Yb ions and a shaped pump core defined by a large NA air cladding. This gave reduced fibre length in an amplifier (compared to a conventional rare earth double clad fibre) providing an advantage with respect to the onset of non linear spectral broadening. Two all-solid photonic bandgap fibres (S-PBGF) for beam delivery from a fibre laser with a wavelength of 1070 nm and simultaneous rejection of stimulated Raman scattering (SRS) light at a wavelength of 1126 nm are presented. The fibres gave larger MFD near 1 μm with SRS suppression than other published results at the time of this work. A new type of leakage channel fibre, called the micro-clad leakage channel fibre (micro-clad LCF), is demonstrated for the first time. This fibre type is intended for both beam delivery and in future fibres with an inner core doped with rare earth ions, for beam generation. I present the fabrication and characterisation of an exemplar fibre with mode area of 1440 μm2. A class of simple antiresonant hollow core fibres are investigated. Various single cladding layer fiber structures are examined. I show that the spacing between core and jacket glass and the shape of the support struts can be used to optimize confinement loss. I demonstrate the detrimental effect on confinement loss of thick nodes at the strut intersections and present a fabricated hexagram fibre that mitigates this effect in both straight and bent condition by presenting radially aligned nodes. This fibre has loss comparable to published results for a first generation, multi-cladding ring, Kagome fibre with negative core curvature and has tolerable bend loss for many practical applications.

Light emitters and detectors in the deep ultraviolet range (DUV) are of great current interest, with applications in water purification, solar-blind photodetectors and communication, biohazard detection, and phosphor-assisted white light emitters. However, DUV optoelectronics based on solid-state heterostructures suffer from low internal and external quantum efficiencies, due to issues relating to their fundamental material properties. These limitations motivate the exploration of new classes of materials for these applications. The recent emergence of two-dimensional (2D) materials has opened up new possibilities in this area, however 2D materials also bring new experimental challenges: particularly the deposition and characterisation of atomic layers, as well as scientific challenges, especially understanding how interactions between the 2D layer and the substrates and/or the environment may affect the properties of the 2D layer. In this thesis, the optical properties of promising materials for deep UV photonics are assessed using a combination of techniques, and the mathematical links between the resulting data are demonstrated. The first part of this work discusses the optical and structural properties of gallium nitride and its alloys, which are the foundation of current optoelectronics, and addresses the optical processes of freestanding and supported 2D hexagonal boron nitride (h-BN) as a potential candidate for high-efficiency deep UV optoelectronic devices. The objectives are to (i) confirm the validity of the models on well-known materials, (ii) determine whether h-BN is a good candidate for deep UV optoelectronics and (iii) whether and how interactions between 2D h-BN with substrates must be taken into consideration. The second part discusses the optical properties of barium zirconate titanate with changes in composition and dimensionality. The objectives are (i) to apply models developed for the nitrides to extract the bulk properties of these oxides, and (ii) to determine whether they are good candidates for deep UV optoelectronics in their 2D form.

In recent years, the whispering gallery mode (WGM) technique has received considerable attention as a novel and extremely sensitive technique for use in sensors. The technique is able to detect target molecules at very low levels and in real time, a capability which cannot be matched by any other detection technique currently in use. With this potential rarely found in common sensors, WGM is becoming one of the most widely used. The WGM set-up is simple and inexpensive. Light generated by a tunable laser, circumnavigates the surface of a resonator through a tapered waveguide. This light is strongly confined inside the microresonator by total internal reflection (TIR). Energy is extracted from the fibre, resulting in a negative peak. The surface of the resonator needs to be functionalised for reacting with the target molecule. If a chemical or biological analyte is to be bound on the surface of the resonator, the negative peak must be shifted. This shift can be used for measuring the amount of the analyte. In view of its exciting potential, it is not surprising that WGM is establishing itself as the detection method of choice, especially in chemical and biomedical applications. The work reported in this thesis is in two sections. In the first part, the use of the WGM technique integrated self-assembled glutathione (GSH) modified gold nanoparticles (Au NPs) on an optical microsphere resonator in an ultrasensitive chemical detection assay for Pb(II) (down to 10 ppt or 0.05 nM) is described. This satisfies the demanding sensitivity required for monitoring the maximum Pb(II) exposure limits set by both International Agency for Research on Cancer (IARC) and the United States Environmental Protection Agency (EPA). The second section presents an example of the use of WGM in a biosensor to study the interactions between small molecules and G-quadruplex DNA which is well known to be active targets for anticancer treatments. Currently methods typically used to study such systems have proven to be valuable; however, they have limitations, such as low sensitivity, time-consuming monitoring and lack of real time analysis. To circumvent these problems, a novel platform based around WGM is developed. The sensor offers a real time, fast and sensitive analysis. In addition, kinetic data such as dissociation equilibrium constant (KD ) as well as association and dissociation constant (kon and koff , respectively) can be easily obtained.

Image registration seeks pointwise correspondences between the same or analogous objects in different images. Conventional registration methods generally impose continuity and smoothness throughout the image. However, there are cases in which the deformations may involve discontinuities. In general, the discontinuities can be of different types, depending on the physical properties of the tissue transitions involved and boundary conditions. For instance, in the respiratory motion the lungs slide along the thoracic cage following the tangential direction of their interface. In the normal direction, however, the lungs and the thoracic cage are constrained to be always in contact but they have different material properties producing different compression or expansion rates. In the literature, there is no generic method, which handles different types of discontinuities and considers their directional dependence. The aim of this thesis is to develop a general registration framework that is able to correctly model different types of tissue transitions with a general formalism. This has led to the development of the eXtended Free Form Deformation (XFFD) registration method. XFFD borrows the concept of the interpolation method from the eXtended Finite Element method (XFEM) to incorporate discontinuities by enriching B-spline basis functions, coupled with extra degrees of freedom. XFFD can handle different types of discontinuities and encodes their directional-dependence without any additional constraints. XFFD has been evaluated on digital phantoms, publicly available 3D liver and lung CT images. The experiments show that XFFD improves on previous methods and that it is important to employ the correct model that corresponds to the discontinuity type involved at the tissue transition. The effect of using incorrect models is more evident in the strain, which measures mechanical properties of the tissues.

The use of copper vapour lasers for laser ablation in laser materials processing applications is studied. To this purpose, the generation of near diffraction-limited beam quality output from a single medium-scale oscillator is demonstrated via matching the total buffer gas pressure to the specific electrical input power loading and the degree of insulation of the plasma tube. The design and characterisation of a Master-Oscillator Power-Amplifier system based on a smallbore oscillator is also described, focusing on pulse stretching techniques to provide efficient seeding required for producing 20-50 W high beam-quality output for laser materials processing purposes. Various experimental studies on the fundamental processes of laser ablation of metals are presented. The effect of the background gas properties on shock-wave formation in laser generated plasmas is studied using a ballistic pendulum. The experimental findings are found to be accurately described by a modified Sedov-Taylor-Von Neumann theory which accounts for the effect of the piston-mass. The theory is applied to characterise the fluorination process in the shock-wave, in view of oxygen isotope analysis in geochemistry. Atomic emission spectroscopy is shown to provide some measure of the electron temperature and electron density at the plasma core. The experimental results are discussed in view of existing models to describe the extreme Stark-broadening and self-absorption in dense, cool plasmas. A comparative study of the use of femtosecond and nanosecond pulsed lasers for laser ablation of metals is presented to assess the relative importance of thermal diffusion. Measurement of the recoil momentum due to ejection of molten particulates during ablation in vacuum provides insight into the effect of material properties. Diffusion-limited surface texturing of metals via direct transfer of an optical interference patterns is demonstrated.