Reflective liquid-crystal-based Spatial Light Modulators (SLM), addressed with optimised Computer Generated Holograms (CGH), have been integrated with two picosecond laser systems to control and manipulate the phase front and polarization states of laser beams, both statically and dynamically, for ultrafast laser surface microstructuring. Firstly, two SLMs were used in combination to structure the optical fields and wavefront of a 532 nm, 10-picosecond laser beam, producing planar or vortex wavefronts with radial or azimuthal polarization states. Multiple first-order cylindrical vector beams with vortex or planar wavefront have been generated and used to nano-structure a highly polished stainless steel metal surface. Then, synchronization of the two SLMs with the picosecond laser system was achieved for dynamic modulation of the polarization states of the laser beam. Consequently, for the first time, four states of polarization, linear horizontal and vertical, radial and azimuthal, all with a ring intensity distribution, were dynamically switched at a frequency up to ν = 12.5 Hz while synchronized with a motion control system and the 532 nm picosecond laser. Surface patterning with these 4 states resulted in ~ 0.5 μm pitch plasmonic structures, easily discernible when using white light diffraction. In separate experiments, CGH's applied to a single SLM were synchronised with a galvo scanner and a 1064 nm, 10 ps laser system for dynamic linear polarisation modulation. This real time polarisation control allowed complex laser surface patterning of polished metals with linear, periodic, ~ 1 μm pitch surface plasmonic structures. Hence, iridescent metal surface colouring with various geometric patterns was achieved. Finally, with an advanced digital scanner fully synchronized with the 532 nm, 10 ps laser system, high speed parallel multi-beam surface patterning of a 30 nm thick Aluminium thin film on a flexible Polyethylene Terephthalate (PET) was achieved. With laser repetition rate of 200 kHz and 8 diffracted first order beams, a film removal rate of R > 0.5 cm2/s was demonstrated with 5W average laser power delivered without damage to the PET substrate. The effective laser repetition rate was f ~ 1.3 MHz. During this work, the single pulse front and rear side single pulse ablation thresholds of the Al film on PET were determined to be Fth= 0.20±0.01 J.cm-2 and 0.15±0.01 J.cm-2 respectively, much lower than the PET ablation threshold, Fth=1.2 J.cm-2, providing a clear processing window.

Plasmonic tweezers and optical tweezers are two techniques for trapping and manipulating particles. Plasmonic tweezers utilizes localized surface plasmon field, whilst optical tweezers utilizes focused laser beam. In this thesis, these two techniques were applied for the manipulation of metallic particles in three basic forms: single particle, particle dimer and particle trimer. Firstly, the trapping of metallic particles was investigated through focused plasmonic tweezers when surface plasmons are excited by focused Radially Polarized Beam (RPB). The force exerted on the metallic particle is responsible for the trapping, which is found to be due to the sum of both gradient and scattering forces acting in the same direction established by the coupling between the metallic particle and focused plasmonic field. This contrasts the repulsion of metallic particles in optical tweezers. Focused plasmonic trapping of metallic particle enables actively moving metallic particle in a controlled way, which could be used for intracellular Surface Enhanced Raman Scattering (SERS) imaging. Secondly, the trapping of horizontally-oriented metallic particle dimers was theoretically studied through focused plasmonic tweezers when surface plasmons are excited by focused linearly-polarized beam. It was found that a Surface Plasmon Virtual Probe (SP-VP) pair was generated on a metal film. A formula is derived to represent the electric field of SP-VP pair, revealing that the spacing of the two virtual probes is wavelength-dependent. Each SP-VP is able to trap a metallic particle, thus the gap between the trapped particles of the dimer can be controlled by changing the excitation wavelength. This theory was further tested by successfully trapping nanosphere and nanorod metallic dimers with 10 nm gaps. The trapped dimer showed a typical electric field enhancement of more than 103 times, which is enough for single molecule SERS detection. Thirdly, a vertically-oriented dimer structure was proposed based on trapping of metallic nanoparticle by focused plasmonic tweezers. The vertically-oriented dimer can effectively make use of the dominant longitudinal component of the SP-VP thus providing much stronger electric field in the gap. Furthermore, for practical application the top nanoparticle of the dimer can be replaced with the tip of an atomic force microscope which enables the precise control of the gap distance of the dimer. Therefore the proposed vertically-oriented dimer structure provides both the scanning capability and the extremely-high electric field enhancement necessary for the high sensitivity Raman imaging. Lastly, the stable trapping and steady rotation of a metallic particle trimer were experimentally achieved by optical tweezers with optical vortex. The trimer particles are found to be confined inside the maximum intensity ring of a focused circularly polarized optical vortex. Theoretical analysis suggests that a large proportion of the radial scattering force pushes the particles together, whilst the remaining portion provides the centripetal force necessary for the rotation. The achieved steady rotation of the metallic particle trimer may lead to the development of microfluidics devices such as micro-rotor.

Commercial testing of Intumescent paints can be extremely expensive. There is a need to develop lab scale systems that can cost effectively both study and test intumescent paints under conditions that are closer to commercial and real time fire tests. This research aims to present a strong case for using an impinging flame based rig to test intumescent coatings. The main feature of using flame impingement is the heterogeneous absorption of heat along the wall surface. This property is a great advantage because intumescent paints under complex fire conditions can be simulated more realistically. The heating technique is coupled with advance diagnostics methods to highlight behaviour that has not been observed before. Physical aspects of commercial coatings, under the new setup, are compared to the cone calorimeter – traditional testing setup The process of intumescence was observed through the use of diagnostic techniques such as Schlieren, thermal and digital imaging. Cross sectional area and surface textures were captured using digital images of fully intumesced char samples that revealed distinct internal structures and surface textures. Temperature of the substrate, Tb, was recorded using a thermocouple attached to the back surface of the panel under different heating conditions. Schlieren technique, based on the refraction of light phenomenon, has never been use to examine the physical aspects of intumescence. It helped highlight the interaction between the flame and paint surface. The impingement of non-reactive fuel, at low separations was clearly visible and was responsible for influencing mode shape of the resulting char. The expulsions phenomenon observed using this technique has not been visually observed before. It occurred during the pustule appearance phase offering conclusive evidence that invisible gases escape from the surface of the paint. The measurement of char expansion and its rate of growth whilst engulfed in luminous diffusion flames is a methodology developed using this technique. The results revealed that formulations tested had unique expansion behaviours and growth pattern. Furthermore, an expansion activation temperature (EAT) range with respect to substrate temperature was identified for each formulation, which was found to be consistent under a variety of experimental conditions. The distinctive yellow colour of a diffusion flames engulfs a coating during a test. Due to this, the process of intumescence has not been observed visually. Thermal imaging was used in this study because it allowed the user to bypass the flame and observe intumescence as it occurred. Using thermal imaging, the physical aspects of intumescence were studied in extensive detail and salient characteristics were identified. The appearance of surface pustules followed by majority of the expansion were characterised as the two distinct phases in the intumescence process. Analysis of the surface temperature revealed that the thermal profile of the surface was non-uniform and highly localized in nature. This was attributed to the higher temperature of the pustules relative to the paint surface. Results from thermal imaging combined well with the Schlieren technique to develop a coherent understanding of the expansion process. Diagnostic equipment, particularly thermal and digital imaging, were also used on tests conducted in a cone calorimeter. The results between cone heater and impinging flame-based tests were compared. The degree of intumescence, surface temperature profile and various characteristics were found to be different between both methods. Finally, the use of the techniques was extended to study the process of intumescence and complex char growth patterns on T-shaped panels coated with intumescent formulations. Char growth was observed to be complex and non-linear as compared to flat panel systems. A novel Image processing algorithm using the thermal imaging data from the cone calorimeter was developed marking a further advancement to the use of this technique and gain insight into the growth mechanism when examining a complicated three dimensional system such T-panels.

In Printed Circuit Board (PCB) manufacturing. making the conductive tracks 3D and embedding the electronic components in substrate can effectively reduce the circuit board volume, and improve the power delivery performance. Laser based additive manufacturing has been developed for many years but currently it is still used to create non-functional product. This PhD work will combine the two technologies together to generate a complete 3D embedded circuit system. hi addition. the laser beam will be reconstructed using Holographic Optical Elements (HOE) to control the microstructure of the product.

Particle shape detection and measurement are important features in the more general field of particle analysis and characterisation. Knowledge of the particle shape is useful in a wide variety of industrial applications. Although it is often practically feasible to use imaging technologies for particle shape analysis, this is not often a sufficiently efficient method for widespread on-line or in situ applications. In many applications it would be sufficient to have an indicator of particle shape, in the same way that a turbidity sensor is an indicator of the amount of particles present. Scattered polarized light from individual particles will be shown as a useful tool for particle shape detection. In principle, the presence of non-spherical particles can be diagnosed by analysing the change in polarisation state following scattering and in particular exploiting a configuration in which spherical particles produce no such changes. The concerns of this thesis are the design and implementation of optical polarimeters for the detection of non-spheres in an aqueous suspension, with particular emphasis on a robust implementation.

This thesis presents advances in the fabrication and application of multicore optical fibres, specifically pertaining to nonlinear endomicroscopy. Chapters 1 and 2 present the necessary background material to understanding the results presented in chapters 3 and 4. Through chapter 1 the properties of optical fibres are described. The basic structure of silica fibres and the parameters used to classify them are discussed. Typical methods of fabrication are outlined along with post fabrication processes. The experimental procedures required in the later stages of the thesis are also covered. Chapter 2 introduces and reviews nonlinear endoscopy. Various nonlinear process involved are described and the current positions of each in the field of nonlinear imaging discussed. In chapter 3 a method for minimising the variation in group indices of cores within a multicore fibre is outlined, experimentally examined and verified. The minimisation is achieved by specifically controlling the core diameters within the multicore fibre for a given wavelength. The fourth chapter introduces a ‘proof of concept’ method for reducing the bend sensitivity of a multicore fibre. Here a helical path is followed by the cores within the fibre. The specific challenges of fabrication are also described.

The emergence of integrated quantum photonics is revolutionising the field of photonic quantum information science and technology. Quantum photonic waveguide platforms, capable of integrating single photon sources, quantum optical circuits and single photon detectors on semiconductor chips by exploring mature micro- or nano-fabrication technology, greatly promise unprecedented complexity, miniaturisation, scalability and robustness for advanced quantum information applications, including quantum communication, sensing, simulation, machine learning and computing. This thesis is to continually enlarge the scope of integrated quantum photonics technology by developing new materials, devices and systems for new functionalities including generation, manipulation, transmission, distribution, interconversion and measurement of photonic quantum states. Gallium arsenide waveguide quantum circuits are first developed to manipulate photons, demonstrating two-photon quantum interference in integrated beamsplitters and manipulation of photon number entanglement in optical interferometers utilising the linear electro-optic effect of gallium arsenide. We also demonstrate a chip-to-chip quantum photonic interconnect, by demonstrating high-fidelity entanglement generation, manipulation, transmission, distribution and measurement across two separate integrated silicon quantum photonic chips. A highfidelity interconversion of path and polarisation encoding preserves coherence across the full interconnected chip-to-chip system. This would allows quantum information encoding, processing and analysing on chips and quantum information transmission and distribution across chips, towards the multi-chip and multi-core quantum systems. We report on-chip generation of high-purity orbital angular momentum states and the fast-speed reconfigurability and switch-ability using an ultra-compact integrated silicon microring resonator embedded with angular diffractive gratings. Quantitive and qualitative measurements are performed to analyse the orbital angular momentum states from the chip. This might allow a high-capacity quantum interconnectivity of free space and integrated quantum circuits for many quantum information prototypes. This thesis demonstrates the capabilities of on-chip encoding, controlling, transferring and analysing quantum states in photon's path, polarisation and spatial modes degrees of freedom, providing a new generation of integrated quantum photonics toolbox for future quantum information technology.

To obtain the crucial information about the boundary layer(Troposphere), there is a need for measurement of large areas( > 25,000 km2) with ne scale measurements of less than 1-2 km area. Over the past years, several methods have been developed to measure atmospheric water vapour fields, but none of them provide information on such small scales( < 1-2 km). With the recent development of high resolution numerical weather model, the need to provide high temporal and spatial data is ever so significant for proper utilization of the model. This thesis presents a novel approach to estimate the water vapour/refractivity from the propagation path link delay by using a network of links. We also present in this thesis a different and unique approach to remote sensing of the atmosphere using broadcast free-view TV signals. The theoretical background into the effects of the radio wave propagation through the lower atmosphere has been explored, thereby laying out the issues and shortcomings of existing remote sensing instruments. The focus of this research is to determine the feasibility of using digital radio and television signals (DVB-T and DAB) data for Tropospheric propagation delay modelling. To estimate the path delay variability of signal propagation through the troposphere we have used the ray tracing approach. For the estimation of phase delay between the transmitter and receiver, a two dimensional ray tracing algorithm was developed to use different atmospheric remote sensing data to calculate the propagation delay in the troposphere. Statistical analysis of the path delays to showing the variation effects due to different seasons, distance and time has been presented. This thesis further describes the retrieval algorithm which uses the path delay from ray tracing to implement tomography inversion modelling technique. The technique uses a network of path link delays to estimate refractivity. The simulation results obtained from this investigation show that water vapour/refractivity can be estimated from path link delays using tomography reconstruction technique.

This thesis investigates nonlinear optical phenomena in non-silica fibres, in a first part utilising a fluoride fibre, followed by the exploration of hybrid fibres with an organic single crystal inside a fibre capillary. The unique properties of 55ZrF4, 18BaF2, 6LaF3, 4AlF3, 17NaF (ZBLAN) glass allow the creation of optical fibres with a highly extended transmission window on the longer wavelength side. We investigated the properties of ZBLAN fibres in order to optimise supercontinuum (SC) generation in a ZBLAN fibre pumped by an optic parametric amplifier. To study applications of the ZBLAN SC we integrated the SC into a pump-probe setup, being used as a near-infrared broadband probe source. We have carried out proof-of-principle measurements on an organic copolymer thin-film, showing the possibility of utilising a ZBLAN SC, allowing to extend the usability of broadband sources to the nearand mid-infrared, while simplifying the usage of the setup. The second part of this thesis explores the possibilities of hybrid fibres by using a hollow-core silica capillary with an organic single-crystal inside. We have developed and optimised a method to grow an organic semiconducting crystal inside a hollow core capillary based on the Bridgman-technique. We could demonstrate the filling of the inner capillary for diameters down to 1 m and with different materials based on the anthracene structure, opening up possibilities for various hybrid fibres. The quality of the single-crystals was evaluated by micro-Raman and X-ray diffraction measurements. We could access nonlinear properties of the crystal by coupling light with an energy lower than the band-gap into the fibre. Stimulated by two-photon absorption photo-luminescence from the fibre core was observed for the hybrid fibre. The results obtained for the hybrid fibres gives rise to a vast amount of possibilities for different hybrid fibres with tailored optical properties of organic materials and their optimisation in the guiding of light.

The terahertz time-domain spectroscopy (TDS) technique which combines broadband and highly sensitive coherent detection with time revolution and strong immunity to background has found application in a wide range of fundamental disciplines. This work presents the development of a polarisation resolved THz-TDS spectrometer that enables sensitive studies of the optical activity of chiral metamaterials in the terahertz frequency range. The thesis is divided into two principal parts. The first (chapters 2 to 4) describes the principles of the time-domain spectroscopy. This is followed by descriptions of a crossed-bowtie antenna which simultaneously detects both orthogonal field components and devices for measuring the state of polarisation of THz waves. In particular we present experimental and computational studies of four linear polarisers. One is a pile-of-plates which relies on the different reflectivity of s and p-polarised light incident on a dielectric surface at Brewster’s angle and the others are wire-grids of different dimensions and different substrates which rely on the anisotropic conductivity of thin metal wires. The design of the polarisation resolved spectrometer and a formalism for describing optical activity and analysis data are then described in the fourth chapter. The second part of the thesis describes applications of the polarisation sensitive terahertz TDS system to the study of optical activity exhibited by artificial materials. Four structures have been studied in this work; metal screw hole arrays, quasi-two-dimensional gammadions and Archimedean spiral metamaterials and a quasi-three-dimensional array of spirals. Experimental and computational studies of the polarisation characteristics and the optical properties of these structures are discussed in chapters 5, 6 and 7.