The research presented in this thesis focuses on the implementation and development of transfer printing as a novel technique for heterogeneous integration of III-nitride based light emitting diodes (LEDs) onto a wide range of substrates, whether flexible or rigid in their nature. The initial steps towards a functioning prototype are described with the successful transfer printing of 2 µm-thick micron-size LEDs. The thin structures were assembled onto mechanically-flexible substrates in a representative 16x16 array format using a modifed dip-pen nano-patterning system. Two different methods of addressing the LEDs were studied by using conductive inks on the LED bonding pads or through the use of metal tracks. Both addressing schemes are compared and studied for reliability. Individual study of the printed array elements showed blue emission centred at 486 nm with a forward-directed optical output power up to 80 µW (355 mW/cm²) when operated at a current density of 20 A/cm². A relatively poor performance was observed with damage to the current spreading metal due to an alkaline wet etch step, needed during processing to yield suspended membranes. This issue was addressed by reversing the order of the major steps needed to fabricate the LEDs, which resulted in signifcantly improved LED performance. The capabilities of the nano-patterning system were demonstrated with successful LED placement as low as 150 nm (±14 nm) between dies. Further optimisation beyond the initial prototypes made use of heat-efficient substrates, namely fused silica and diamond, without the use of intermediary adhesion layers. Through the use of a liquid capillary bond, consistent van der Waals bonding was achieved, despite the curvature of the epitaxial layers that comprise an LED following their release from their native silicon growth substrates. The excellence of diamond as a heat-spreader allowed the printed membrane LEDs to achieve optical power output density of 10W/cm² when operated at a current density of 254 A/cm² - a signifcantly higher operational regime compared to the initial prototypes. To capitalise on the new achieved performance, demonstrations of data transmission and colour conversion are shown.

This thesis examines metal nanoparticle/agarose (MNPA) gel composites and highly ordered metal nanorod arrays, fabricated by guided nucleation during oblique angle deposition (OAD), as surface-enhanced Raman scattering (SERS) substrates. The effectiveness of MNPA has been effectively demonstrated previously using silver nanoparticles (AgNPs), but it is poorly understood how different NP growth conditions affect the SERS response. SERS intensity of gold and silver NPA is examined in detail as a function of salt and (by default) reducing solution concentration, and the effect of using different reductants is also investigated; reproducibility of selected gels is carefully explored. In addition, SERS of highly ordered Ag and copper (Cu) nanoarrays is examined in depth. Normally, OAD generates a random nanorod distribution on flat supports, where nucleation is a random process. This however hinders the control of geometrical parameters such as rod separation and diameter which directly affect the SERS response, an effect mitigated by introducing a guiding element to influence nucleation. Until recently, only semiordered SERS-active Ag nanorod arrays had been accomplished by OAD. These however depended on time-consuming and expensive electron beam lithography (EBL) to write a template to guide nucleation and the subsequent growth of nanorods. Importantly, lengthy fabrication times force a practical upper size limit on the substrate, meaning it is exceedingly small which drastically reduces its potential for sensing applications. It also severely restricts the number of substrates which can be produced in a given time. This thesis addresses these issues via the construction of highly ordered, SERS-active, large-area Ag and Cu nanorod arrays, using a cheap, large-scale, nanoimprinted polymer template to influence nucleation during the initial stages of OAD. Moreover, OAD is a high throughput method, as it permits the simultaneous fabrication of several substrates during a relatively short deposition cycle.

This work encompasses characterisation of defects and dosimetric studies of novel tailor made doped SiO2 fibres. Present studies have been carried out seeking to improve upon the thermoluminescence (TL) yield of commercially produced small diameter telecommunication optical fibres. Using the modified chemical vapour deposition (MCVD) process, the optical fibres have been fabricated to a range of dopant concentrations of nominal value 6- 8- and 10 wt%. In this study, three different types of optical fibres have been utilised, made using the same doped preform. The doped fibres are cylindrical fibres (CF), flat fibres (FF) and photonic crystal fibres (PCF). It should be noted that the process of fibre drawing has been found to produce defect centres, influencing characteristics of optical fibre and TL response. To seek support of this, an X-ray Photoelectron Spectroscopy (XPS) study of a Ge doped SiO2 fibres sample has been undertaken to determine the oxidation state of Ge. Results from this have confirmed the efficiency of the surface analysis technique, leading to understanding of the Ge structure. Following on from this, facilities supporting characterization of the fibres are outlined, including an ion beam facility used for Particle Induced X-ray Emission (PIXE)/Rutherford Back Scattering (RBS) analysis to localize and determine the concentration of Ge dopants. Building upon these characterisations, thermoluminescence studies were carried out. For the first of the experiment, undoped flat fibres were used, comparison of response being made with that of conventional TLD-100 and commercial Ge-doped silica fibres. The undoped flat fibres provide competitive TL yield to that of TLD-100, being some 100 times that of the Ge-doped fibres. Pt-coated flat fibres have then been used to increase the photoelectron production and hence local dose deposition, obtaining significant increase in dose sensitivity over that of undoped flat fibres. Using 250 kVp X-ray beams, the TL yield reveals a progressive linear increase in dose for Pt thicknesses from 20 nm up to 80 nm. Finally, to illustrate the potential of novel tailor-made doped SiO2 optical fibres, the dosimetric characteristics that have been investigated include, dose response, glow curves and energy dependence. Taking TLD-100 as a benchmark, results are presented for Ge-doped, Ge-B-doped and Ge-Br-doped optical fibres. The dose response of doped silica fibres was found to be linear over the range 2 cGy up to 50 Gy, also showing good dosimetric response for low photon energies. Additional investigation of the same doped SiO2 optical fibres have been conducted for measurement of TL yield from the high linear energy transfer (LET) radiation offered by a liquid 223Ra alpha particle source.

Diamond's unrivalled thermo-mechanical and optical properties make the material an attractive material for use in laser systems. Improvements in growth techniques over the past decade have led to a surge of research employing diamond in optical systems. This thesis presents the characterisation of diamond and its implementation in Raman lasers, utilising the materials high Raman gain as well as its impressive thermal properties. Diamond's potential as both an extremely compact and robust method for frequency conversion, allowing access to relevant but otherwise hard to reach wavelengths, and also as a means to convert low brightness sources to near diffraction limited beams will also be discussed. A pump-probe measurement is used to conduct the first systematic study of the Raman gain in diamond over a wide range of wavelengths, from 355nm to 1450nm, with a dependence observed. Using the high Raman gain measured, both CW and pulsed Raman systems were designed and characterised. An 11-fold brightness enhancement was achieved in an Nd:YAG pumped intra-cavity diamond Raman laser, while record powers of 7.6W are presented using an Yb:LuAG pumped diamond Raman laser. Two monolithic diamond Raman lasers are discussed, achieving near quantum limited conversion efficiencies. An investigation of the laser induced damage threshold of diamond surfaces is conducted, with attempts made to improve the measured value of 25Jcm-2 discussed.

This thesis describes experiments thatexplore the possibility of improving the quality of an electron beam obtained from a laser wakefield accelerator (LWFA) by shaping the longitudinal plasma density profile. Different density profiles have been obtained by employing a range of Laval nozzles with different geometries. These are modelled and numerically simulated under different conditions using Fluent 6.3. Density lineouts from simulations for different heights above the nozzle give the plasma density profile for each experimental condition. The plasma density profile is modified by changing the geometry of the nozzle, the interaction point, the laser beam angle relative to the exit plane of the nozzle and pressure of the gas. In this way the leading up-ramp length of the density profile (that interacts first with the laser) has been varied between 0.47 mm to 1.39 mm and the maximum plasma density varied between 1.29 x 1019 cm⁻³ to 2.03 x 1019 cm⁻³. The influence of the density profile parameters on the LWFA process is quantified by monitoring the properties of the generated electron beam. It is shown that the leading ramp of the plasma density profile i.e. the ramp that interacts first with the laser, has a strong influence on the quality of the electron beam. Density profiles with the same peak plasma density but different ramp lengths generate electron beams with a factor of 1.4 difference in charge, 1.1 in electron energy, 2 in pointing and 1.45 in energy spread. Longer ramp lengths enhance the quality of electron beams, which suggest that LWFA injection occurs at the entrance density ramp. Complex density profiles are produced by tilting the nozzle relative to the direction of propagation of the laser. This allows continuous tuning of the peak energy of the electron beam from 135 ± 2MeV up to 171 ± 2MeV. The electron beam energy spread show improvements from 20.7 ± 1.2% to 8.9 ± 0.9%. The charge closely follows the evolution of the energy spread and has a mean value of 0.61 ± 0.16 pC. Experimental results also show that the angular distribution of the electron beam becomes elliptical when the laser focal plane is moved from the edge of the gas jet towards the centre of the density profile. This result is linked to the existence of a distorted LWFA bubble that propagates off-axis therefore affecting the pointing and transverse shape of the electron beam.

Proteins are complex molecular machines that facilitate the chemical reactions fundamental to life. Their functions are encoded in a linear sequence of amino acids, of which only 20 species are found in nature. Yet the functional and structural diversity accessible through these building blocks is vast. Molecular and atomic-level protein studies have been crucial to our understanding of health and treatment of disease, with increasingly sophisticated experimental and computational methods continuing to provide new information with which to advance medicine. However, the requirement for more detailed understanding of proteins has risen through the emergence of multi-antibiotic-resistant bacteria and also through the potential to design synthetic proteins of novel function. Paradigms of protein function have evolved significantly since early studies, though few all-encompassing descriptions have been proposed, owing to the complex, dynamic structures of these large biomolecules. Presently, the relationship between protein structural motions at different timescales appears to hold vital significance to the elusive aspects of biological mechanisms. No single measurement technique is capable of accessing the multitude of timescales over which protein motions occur, and thus concerted investigation is necessary. Observation of dynamics at the femtosecond-picosecond timescale has only recently become possible through the development of new experimental techniques, allowing a new class of protein motions to be investigated. In this thesis, the advanced technique of two-dimensional infrared spectroscopy (2DIR) is employed to study three biomolecular systems with implications to ubiquitous protein interactions. The aims of these investigations are, firstly, to demonstrate the suitability of 2DIR spectroscopy in gathering novel dynamic information from biological systems that is not accessible via other methods, and secondly, to derive the potential physical significance of these dynamics as they relate to biological function. A description of the underlying theory of 2DIR is presented in this Chapter, along with the considerations that must be made in the application of such a technique to complex biological case-studies. In Chapter (2), descriptions are given for the experimental setups used to acquire infrared spectra, specifically, Fourier transform infrared (FTIR), pump-probe and 2DIR spectroscopies. In Chapter (3) the catalytic-site dynamics of two closely-related haem proteins are each studied by monitoring the vibrational evolution of a nitric oxide (NO) probe molecule bound to the haem centre. A comparison of the active site dynamics is performed in order to correlate the observed differences with discrepancies between the protein reaction mechanisms. Chapter (4) explores the potential of a coenzyme with high protein-binding promiscuity to serve as an intrinsic reporter of the dynamics that occur at substrate binding sites. Infrared analysis and categorisation of the free coenzyme molecule is performed in order to establish its effectiveness as a probe. In Chapter (5), method-development strategies are proposed for the extraction of 2DIR data from large, complex protein-protein systems, with the objective of expanding the range of interactions on which 2DIR can effectively report. Both well-established and novel strategies are employed, and the potential and limitations of the technique are discussed in the context of these demanding case-studies. Chapter (6) draws together conclusions and an overview of progress made and discusses future directions.

Gamma ray spectroscopy is routinely used to measure radiation in a number of situations. These include security applications, nuclear forensics studies, characterisation of radioactive sources, and environmental monitoring. For routine studies of environmental materials, the amount of radioactivity present is often very low, requiring spectroscopy systems which have to monitor the source for up to 7 days to achieve the required sensitivity. Recent developments in detector technology and data processing techniques have opened up the possibility of developing a highly efficient Compton Suppressed system, that was previously the preserve of large experimental collaborations. The accessibility of Monte-Carlo toolkits such as GEANT4 also provide the opportunity to optimise these systems using computer simulations, greatly reducing the need for expensive (and inefficient) testing in the laboratory. This thesis details the development of such a Compton Suppressed, planar HPGe detector system. Using the GEANT4 toolkit in combination with the experimental facilities at AWE, Aldermaston (which include HPGe detection systems, scintillator based detector systems, advanced shielding materials and gamma-gamma coincidence systems), simulations were built and validated to reproduce the detector response seen in the 'real-life' systems. This resulted in several improvements to the current system; for the shielding materials used, terrestrial and cosmic radiation were minimised, while reducing the X-ray fluorescence seen in the primary HPGe detector by an order of magnitude. With respect to the HPGe detector itself, an optimum thickness was identified for low energy (<300 keV) radiation, which maximised the efficiency for the energy range of interest while minimising the interaction probability for higher energy radionuclides (which are the primary cause of the Compton continuum that obscures lower energy decays). A combination of secondary detectors were then optimised to design a Compton Suppression system for the primary detector, which could improve the performance of the current Compton Suppression system by an order of magnitude. This equates to a reduction of the continuum by up to a factor of 240 for a nuclide such as Co-60, which is crucial for the detection of low-energy, low-activity emitters typically swamped by such a continuum. Finally, thoroughly optimised acquisition and analysis software has also been written to process data created by future high sensitivity gamma coincidence systems. This includes modules for the creation of histograms, coincidence matrices, and an ASCII to binary converter (for historical data) that has resulted in an analysis speed increase of up to ~20000 times when compared to the software originally used for the extraction of coincidence information. Modules for low-energy time-walk correction and the removal of accidental coincidences are also included, which represent a capability that was not previously available.

A theoretical model has been developed to predict the excitation energy, spin and parity distributions of the residual nuclei following a (p,t) two-neutron transfer reaction. These distributions may be compared with those expected for the same residual nucleus produced via an (n, ) reaction and therefore provide information on whether (p,t) can be used as a suitable surrogate in cases where an (n, ) reaction cannot be observed directly. The model developed predicts the possible spin, parity and energy values of the discrete excited states populated in the residual nucleus and calculates the absolute strength of each transition, including both the dynamical and structural components of the cross section. The model has been designed to be purely predictive and to require little or no detailed prior information on the target nucleus in question. The model developed has been applied to the case of 28.53 MeV protons incident on an isotopically enriched 92Zr target, a case for which experimental data have recently been taken by another research group using the STARLiTeR detector at Texas A&M University. Data exist for the triton energy spectrum, triton angular distributions in the range � � 25� - 60�, and coincident -ray decay spectra. A detailed comparison between the model and data shows a reasonable match to the average trends, but a breakdown when individual discrete states are scrutinised in detail. In particular, the model fails to predict the population of a number of physical states observed in 90Zr, suggesting a more sophisticated approach to the structural and/or dynamical components of the model is required. Possible alternative methods and extensions to the physics of the model, in order to address the discrepencies with the measured data and to allow the model's application to more diverse physical systems, are also discussed.

A passively shielded, low-background hyper-pure germanium detector system was used to analyze and determine the radioactivity levels and content of soil samples taken from across the State of Kuwait. Samples were collected from 180 separate locations using a grid pattern with a 10km grid spacing with the result of creating a surface radiological map of the State of Kuwait. It was found that naturally occurring radioactive materials, 238U, 232Th and 40K, had average concentrations of 18.5±4.3, 17.1±4.1 and 410 ±110 Bq/kg respectively. Artificially created radionuclides were not found or were below the minimum level of detection. The Radium Equivalent Activity was determined to be 26.1±2.9 . Analysis was also carried out on isotopic abundances of uranium to determine any locations for evidence of enriched or depleted uranium deposits and/or elevated levels of 226Ra arising from fractionation effects. Typical elemental concentrations of uranium, uhorium and potassium in the samples across Kuwait were found to lie in the range 0.63±0.01 to 2.39±0.04 ppm, 1.34±0.03 to 6.70±0.11 ppm and 0.40±0.03 to 2.53±0.19 ppm respectively. Correlations between uranium, thorium and potassium abundances were measured, with clear correlations between the measured uranium and thorium elemental abundances.

As we move into the next century, photonics will play a significant role in the exploration of the frontiers of science. Photonic materials have the ability to control the flow and generation of photons, and offer greater control over material properties, which can potentially provide solutions to the optoelectronics industry, i.e. improving the current limit in the speed and the capacity of optoelectronics devices. In 1987, a novel class of artificial structures named as ‘photonic crystal’ (PhC), was invented for the inhibition of spontaneous emission and the localisation of photons, which offers control on absorption, emission and propagation of light. Photonic crystals are long-range periodic materials with a periodicity of the order of the wavelength of light. It is the periodicity in refractive index, which determines the allowed and forbidden bands for the light frequency in the photonic crystals. This periodic structure generate Bragg diffractions which result in forbidden frequency in specific propagation directions, so called photonic stop bands. When light propagation is forbidden in a specific range of frequencies in any direction inside the crystal and polarization a complete photonic bandgap is achieved. There are three types of photonic crystals: one-dimensional (1D), two-dimensional (2D) and three-dimensional (3D) photonic crystals, which depend upon the periodic modulation of the dielectric constant i.e. either created in one, two or three dimensions. This thesis deals with the fabrication and analysis of 3D photonic crystals which shows strong confinement of light in three dimensions. In this thesis, we will introduce two different types of 3D photonic crystals i.e. pristine (undoped) and infiltrated (doped) with different nanomaterials fabricated by soft lithographic method i.e. self-assembly. The fabrication 3D photonic crystal is very challenging task, one need to build up high-quality 3D photonic crystals environments. By 1991, Yablonovitch had demonstrated the first three-dimensional photonic band-gap in the microwave regime by drilling an array of holes in a transparent material, where the holes of each layer form an inverse diamond structure – today it is known as Yablonovite. Over the years state-of-the-art fabrication technologies have been developed to fabricate 3D photonic crystals operating in different range of electromagnetic spectrum ranging from near-infrared to visible wavelength ranges. However, these sophisticated fabrication techniques are expensive and time consuming. Soft lithography is another inexpensive versatile route to fabricate photonic structures. The research conducted in this thesis targets building up a solid and comprehensive study on the fabrication of 3D photonic crystals in the technically important visible wavelength range. This project revolves around the fabrication of undoped photonic crystals (pristine) and in-filled photonic crystals with two dimensional layered nanomaterials such as graphene and boron nitride and 1-dimensional materials (single walled carbon nanotubes). Natural gravitational sedimametaion method has been used to fabricate photonic crystals using latex polymer as a 3D template. Despite potential advantages, there are hardly any reports concerning layered nano-filler based photonic crystals (PhCs). In particular, layered two-dimensional based carbon (Graphene), transition metal dichalcogenides (TMDs: Molybdenum disulphide, Tungsten disulphide) and one dimensional materials such as carbon nanotubes are of particular interest due to the high level of optoelectronic functionality they can impart. One of the biggest issues is to produce large quantity of these nano-fillers and, at the same time maintain the quality as well. Once a stable source of nanoparticles is established achieving a homogenous and controlled distribution of these fillers within a polymer matrix is still an obstacle commonly encountered in the fabrication of nanostructures. To overcome this problem self-assembly of latex particles has been used to fabricate two and one dimensional based photonic crystals. During the self-assembly process the individual polymer particles deform into rhombic dodecahedra, due to capillary forces as the polymer dries. Highly ordered polymeric crystals can be produced by this novel technique. This dodecahedra assembly of polymer particles act as a template to assemble nano-fillers, by forcing the nanoparticles to fill the interstitial sites and create three-dimensional, hexagonal patterns. This assembly technique generates a highly uniform distribution of the filler throughout the polymer matrix. One of the key features of our fabricated photonic crystals is the preparation technique i.e. natural, gravitational, sedimentation which makes it very cost effective and efficient. In this thesis, for the first time, colloidal photonic crystals, embedded with such nano- fillers have been fabricated using a novel and facile latex technology. We also propose that this technique is general and can be applied for a range of other two-dimensional and one-dimensional materials. Critically it is demonstrated that the choice of filler influences the optical and mechanical properties of the resultant crystals. This thesis also demonstrates that the optical properties can also be manipulated mechanically , post-processing, using stretching, compression and humidity, demonstrating their potential as sensors and visual indicators which will greatly extend their applications in various fields such as optical sensing materials and various optical devices.