Glasses systems based on TeO2-ZnO-Na2O (TZN), TeO2-WO3, and TeO2-Na2O-ZnF2 are reported here, with a number of other components added (PbO, GeO2, Nb2O5, Bi2O3, Er2O3, Yb2O3, PbF2, and ErF3). Glass formation was shown for the first time, to this author's knowledge, in the ternary system (90-x)TeO2-10Na2O-xZnF2 for x = 5 to 30 mol. %. Glass stability (Tx-Tg) was found to increase with ZnF2 addition, reaching a plateau of around 161oC at x = 25 mol. %. This could be due to competition of various phases to crystallise (NaZnF3 and Zn2Te3O8) as the eutectic is approached, with fluoride addition. These glasses are the most stable ZnF2 containing tellurite compositions reported to date, to the author's knowledge. As-received ZnF2 batch material was shown to contain a significant proportion of Zn(OH)F, identified by XRD. The as-received ZnF2 was fluorinated with (NH4)HF2, which produced a substantially more phase pure powder, with oxygen levels reduced from around 13.2 to 3.1 at. % from XPS spectra. By calculation from the O1s XPS peaks, the proportion of Zn(OH)F was reduced in the powders from 39.7 to 9.4 mol. %. A number of absorption bands in the infrared were identified by FTIR for the TeO2 -ZnO-Na2O glasses due to intrinsic lattice vibrations (visible in a 0.2 mm sample), and extrinsic impurity absorption, including: free OH (around 3.0 microns, 3300 cm-1), weakly hydrogen-bonded OH (around 3.3 microns, 3060 cm-1), and strongly hydrogen-bonded OH (around 4.8 microns, 2090 cm-1). For the series (90-x)TeO2-10Na2O-xZnF2, mol. %, x = 5 to 30 mol. % melted for 2 hours as bulk glasses, OH bands at 2900 cm-1 were reduced in intensity with ZnF2 addition due to self drying of the melt, from around 0.12 cm-1 (120 dB.m-1) for x = 5 mol. %, to around 0.02 cm-1 (20 dB.m-1) for x > 15 mol. %. Melting time also had a significant effect on drying of this series, with the loss at 2900 cm-1 reduced by two orders of magnitude when increased from 1 hour (around 705 cm-1, 705 dB.m-1) to 2 hours (0.01 cm-1, 10 dB.m-1). Refractive index of the series (90-x)TeO2-10Na2O-xZnF2, mol. %, x = 5 to 30 mol. % decreased linearly with ZnF2 addition, from 2.02 (x = 5 mol. %) to 1.85 (x = 30 mol. %), as the fluoride and zinc are less polarisable than oxygen and tellurium. Cohen-Grest viscosity modelling was used to predict the fibre drawing temperature (around 330oC, corresponding to a viscosity of 10^4.5 Pa.s), and fragility of the fluorotellurite core / clad pair (20 / 25 mol. % ZnF2), occurring at least 60oC < Tx. Fragility of these glasses was predicted to lie between oxide tellurite glasses (stronger) and fluorozirconate glasses (more fragile). Increasing melting time and fluorination resulted in a significant decrease in OH bands in the 700 nm to 2.5 micron region for unstructured 70TeO2-10Na2O-20ZnF2 mol. % fibre, from around 40 to 4 dB.m-1 at 2.5 microns as melting time was increased from 3 to 10 hours. Fibre optical loss for the 10 hour melt was relatively flat (around 5 dB.m-1) over the entire 700 nm to 2.5 micron region.

Urban ground motion due to natural or man-made geological processes is an issue of major importance for local authorities, property developers, planners and buyers. Increased knowledge of this phenomena would benefit all involved but the measurement techniques in common use have either spatial or temporal inadequacies. A technique known as Persistent Scatterer Interferometry (PSI) has been developed which can map ground motion to high precision over large areas with a temporal scale measured in years. PSI takes advantage of the high number of Synthetic Aperture Radar (SAR) images available to mitigate the atmospheric effects that inhibit standard Interferometric SAR (InSAR) techniques. This however involves assumptions about the nature of atmospheric variability, such as its randomness over time, or its spatial extent. In addition, little is known about the Persistent Scatterers (PS) themselves and PSI is only able to provide results relative to a reference PS. The reference PS point is often arbitrarily chosen and may itself be in an area undergoing ground motion, thus adding a degree of ambiguity to any relatively derived motion. The purpose of this work is to investigate possible solutions to these shortfalls and quantify any improvements made. A corner reflector network is established in the Nottingham area of the UK. A data archive is collated over three years containing Global Positioning System (GPS) data at the corner reflector sites, data from surrounding Continuous GPS (CGPS) sites and levelling data. Due to conflicts with the European Space Agency (ESA) Environmental Satellite (ENVISAT), there were insufficient SAR images to com- pute a fully integrated corner reflector PSI study. Instead, the project focussed on atmospheric correction of PSI results using absolute ZWD estimates. Zenith Wet Delay (ZWD) estimates are derived from a Precise Point Positioning (PPP) GPS processing method which does not rely on a network of ground stations and therefore produces absolute ZWD estimates which are less prone to biases and noise. These are interpolated across a PSI study area and used to mitigate the long wavelength effects of atmopheric water vapour in the PSI differential interferograms. The corrected PSI results are then compared to uncorrected results, GPS derived motion and levelling data. Results between the ZWD corrected PSI study and the uncorrected study show statistical improvements in some areas and reductions in others. Correlation factors between double-differenced levelling observations and double-differenced PSI results improve from 0.67 to 0.81. PSI deformation rates also show improvement when compared to GPS deformation rates, although some results do not satisfy statistical tests.

A Shack Hartmann wavefront sensor is used to detect the distortion of light in an optical wavefront. It does this by sampling the wavefront with an array of lenslets and measuring the displacement of focused spots from reference positions. These displacements are linearly related to the local wavefront tilts from which the entire wavefront can be reconstructed. In most Shack Hartmann wavefront sensors, a CCD is used to sample the entire wavefront, typically at a rate of 25 to 60 Hz, and a whole frame of light spots is read out before their positions are processed. This results in a data bottleneck. In this design, parallel processing is achieved by incorporating local centroid processing for each focused spot, thereby requiring only reduced bandwidth data to be transferred off-chip at a high rate. To incorporate centroid processing at the sensor level requires high levels of circuit integration not possible with a CCD technology. Instead a standard 0.7J..lmCMOS technology was used but photodetector structures for this technology are not well characterised. As such characterisation of several common photodiode structures was carried out which showed good responsitivity of the order of 0.3 AIW. Prior to fabrication on-chip, a hardware emulation system using a reprogrammable FPGA was built which implemented the centroiding algorithm successfully. Subsequently, the design was implemented as a single-chip CMOS solution. The fabricated optical centroid processor successfully computed and transmitted the centroids at a rate of more than 2.4 kHz, which when integrated as an array of tilt sensors will allow a data rate that is independent of the number of tilt sensors' employed. Besides removing the data bottleneck present in current systems, the design also offers advantages in terms of power consumption, system size and cost. The design was also shown to be extremely scalable to a complete low cost real time adaptive optics system.

Syften med studien är att undersöka vilka läs- och skrivinlärningsmetoder verksamma lärare använder sig av samt vilken syn lärarna har på läs- och skrivinlärning. Våra frågeställningar berör även de faktorer som påverkar läs- och skrivinlärningsprocessen. Studien är en kvalitativ intervjustudie där fyra verksamma lärare har deltagit. Intervjuerna är gjorda i tre olika kommuner i södra Sverige. Resultatet visar att lärarna använder sig till största del av Phonics metoden men med inslag av andra metoder. Lärarna tryckte på vikten av att kunna alternera mellan olika metoder för att kunna tillgodose alla elevers behov. Resultatet visar även att samtliga lärare betonade att läs- och skrivinläringen är en viktig grund för elevers kommande skolgång.

One of the most exciting areas of research in optics is rare-earth doped glasses and fibres with capacity for near-infrared to mid-infrared operations. In particular, there is great interest in optimising parameters like ion concentration, fibre length/geometry, and pump conditions for applications in photoluminescence, amplification and lasing. Round trip investigation from material fabrication, experimental setup and actual device can be laborious, expensive and come with some uncertainties. Some of these uncertainties are accurate identification of ion-ion interactions, impact of such interactions on device performance, correct extraction of phenomenological material properties and the prediction of combination of properties with numerical methods. In this thesis, the spectroscopic behaviour of rare-earth doped materials are theoretically studied via numerical simulations and experimentally verified. The models developed are applicable to steady-state and transient behaviour of rare-earths under different excitation conditions. For the simulation, a couple of spectroscopic parameters are needed which have to be obtained in advance from bulk glasses. Parameters like radiative and non-radiative lifetimes are calculated by complementing theoretical analysis with a few experimental measurements. The first part of the research concentrates on the study of ion-ion interactions in different concentrations of erbium doped sol-gel SiO2 prepared by the sol-gel method. The work includes continuous-wave (CW) and pulsed excitation spectroscopic measurement on the glasses that provide data for the model. These measurements together with the rate-equation modelling are used to obtain a physical understanding of the processes responsible for the fluorescence features observed. A particle swarm optimisation technique was used to predict the values of the ion-ion interactions. The behaviour of the 488 nm and 800 nm excitations were consistent with the predictions of the model. Indeed, the agreement between the calculated photoluminescence and the measured emission indicates that the six important processes that influence the ion-ion interactions in the bulk material have been correctly identified and included. With this model of photoluminescence at hand, it was possible to extend it to laser or amplifier configurations. Subsequently, erbium doped ZBLAN glass fibre with lower phonon energy were explored for lasing in the mid-infrared for application to 2.73 µm high-power delivery for tissue surgery. Accurate laser characteristics were predicted for two different designs, including the ultimate thermal designs. Optimum boundary conditions of mirror end-facet reflectivity, fibre length and effects of modelling parameters were addressed. The study is complimented with experimental data of double-clad fibre and the results reported were a clear documentation of the design of erbium doped ZBLAN fiber laser. Finally, the potential of P r3+ doped chalcogenide (GeAs(Ga/In)Se) glass for photoluminescence and lasing at 4.73 µm is studied. This is to answer the research question - Can we extract the spectroscopic parameters and also model the superior property of these novel glasses?. The laboratory facilities and availability of experimental data were decisive in the choice of praseodymium ions as well as inclusion of Gallium or Indium for this part of the research. The superior characteristics of Indium over Gallium for hotoluminescence and consequently device characteristics were studied with the aid of a rate equation model. The phenomenon of photon reabsorption in the chalcogenide fibres were also simulated and verified with experiment. The work has produced a comprehensive numerical model for the simulation of photoluminescence in P r3+doped selenide based chalcogenide glass and fibre from NIR to mid-IR especially in the Gallium and Indium based analogues.

This thesis presents the study of a relatively new class of photonic structures in-voking Parity-Time (PT)-symmetry. PT-symmetric structures in photonics, as a realisation of PT-symmetric Quantum Mechanics problems, are constructed by a judicious design of refractive index modulation which requires the real part of the refractive index to be an even function and the imaginary part of the refractive index to be an odd function in space. PT-symmetric structures in the form of Bragg gratings, coupled resonators and chain resonators are the main configurations studied in this thesis. These PT-symmetric structures feature a spontaneous symmetry breaking at which interesting wave behaviour such as an asymmetric response depending on the direction of the incident wave, unidirectional invisibility, simultaneous coherent-perfect absorber lasing and localised termination modes are observed; these behaviours are presented in this thesis. Theoretical and numerical studies of these PT-symmetric structures are undertaken which assume realistic material parameters,including material dispersion and material non-linearity. Moreover,in this thesis, potential applications of these PT-symmetric structures are explored. The first part of the thesis considers PT-symmetric Bragg grating structures which are formed by introducing a PT-symmetric refractive index modulation into a Bragg grating structure. If gain/loss dispersion is considered, it is shown that dispersion limits the PT-symmetric operation to just a single frequency. As such spontaneous symmetry breaking can only be achieved by varying the gain/loss parameter. Nevertheless, it is shown that by switching the gain/loss in the system, a switching operation can be achieved by using the PT-Bragg grating at a single frequency. Subsequently,anon-linear PT-Bragg grating is investigated by using a time-domain numerical method, namely the Transmission-Line modelling (TLM) method. For the present work a TLM code is developed from scratch in order to ensure full-flexibility when modelling a dispersive and non-linear material. Using the TLM solver, it is demonstrated that gain/loss saturation is an important material property which should be considered as it may impact the practical applications of a PT-symmetry-based device. In the context of a non-linear PT-Bragg grating (NPTBG), the gain/loss saturation affects the interplay between the PT-symmetric opearation and the Kerr non-linear effect. It is further shown that gain/loss saturation plays a crucial role in securing a stable operation of non-linear PT-based devices. For practical applications, it is demonstrated that a non-linear PT-symmetric Bragg grating offers an additional degree of freedom in their operation,by modulating the gain/loss and the intensity of the input signal,compared to a passive structure which can only be manipulated by the input signal intensity. Two applications based on the interplay of PT-symmetric behaviour and Kerr non-linearity are demonstrated,namely a memory device and a logic-gate device. The second part of the thesis studies PT-symmetric resonator structures as a coupled system and as a periodic chain system. For these studies, a semi-analytical method based on the Boundary Integral Equation (BIE) method is developed and used together with a two-dimensional TLM method. The impact of realistic material parameter on the spectral properties of the structure is again investigated. It is shown that the PT-symmetric behaviour can be observed at a single frequency. Moreover, it is shown that PT-symmetry-like behaviour is observed but with complex eigenfrequencies due to the radiation losses; this is a deviation of the strict definition of a PT-symmetric structure with balanced gain and loss. Lowering lasing threshold by increasing loss in the system is demonstrated; this occurs due to induced early symmetry breaking. The final part of the thesis studies the spectral properties of an infinite and finite chain of PT-symmetric resonators. It is shown that the type of modulation along the PT-chain affects the position of the breaking point of the PT-structure. For a finite PT-chain structure, and for a particular type of refractive index modulation, early PT-symmetry breaking is observed and shown to cause the presence of termination states which are localised at the edge of the finite-chain resulting in localised lasing and dissipative modes at each end of the chain.

This thesis presents an investigation into the properties of III-VI metal chalcogenide semiconductor nanosheets and demonstrates their capability to enhance graphene-based optoelectronics. Strong quantization effects and tunable near-infrared-to-visible (NIR-to-VIS) photoluminescence emission are reported in mechanically exfoliated crystals of gamma-rhombohedral semiconducting InSe at room temperature. The optical properties of InSe nanosheets differ qualitatively from those reported for transition metal dichalcogenides and indicate a crossover from a direct-to-indirect band gap semiconductor when the InSe nanosheet thickness, L, is reduced to a few nanometres, corresponding to the emergence of a ‘Mexican hat’ energy dispersion for the valence band. At low temperature, radiative recombination of photoexcited carriers bound at native donors and acceptors in nominally undoped InSe nanosheets is observed. A two-dimensional hydrogenic model for impurities is used to describe the increase in binding energy with decreasing L and reveals a strong sensitivity of the binding energy on the position of the impurities within the nanolayer. The application of a magnetic field, B, perpendicular to the plane of InSe nanosheets induces a marked change of the observed optical spectrum. A transfer of intensity from a low-to-high energy component at high B corresponds to an indirect-to-direct band gap crossover, which arises from the Landau quantisation of the in-plane carrier motion and crossover between hole cyclotron orbits centred on closed edges of the valence band. High broad-band (NIR-to-VIS) photoresponsivity is achieved in mechanically formed InSe–graphene van der Waals heterostructures, which exploit the broad-band transparency of graphene, the direct bandgap of InSe, and the favourable band line up of n-InSe with graphene. The photoresponse is dependent on the electron transit time through the InSe layer, as evaluated by a semiclassical model.

During these last decades there´s been a debate concerning children’s reading and writing skills. The opinion has been that children does not reach the goals in the curriculum. This study is focusing on the positive and negative sides in Phonics and Whole Language. It is also a presentation of the Witting Method and if this method can be a contributed factor when it comes to reaching curriculum goals.

Owing to their vitreous nature and mid-infrared (MIR) transparency, chalcogenide glasses are a promising material for remote hyperspectral imaging. For medical applications, such as in-vivo cancer diagnosis, Ge-Sb-Se glasses are a particularly interesting material since, it is believed that Sb-containing chalcogenides are less toxic than their As-containing equivalents. For passive optical fibres which aim to deliver and collect MIR light to and from tissue samples, the main challenge which faces their performance is the removal of extrinsic optical losses. Hence, this Project explores and develops high purity Ge-Sb-Se/S bulk glasses and optical fibres. Focussing on the GexSb10Se90-x atomic % (at. %) glass series, bulk samples are initially characterised before the fibre-drawing capability of each composition is assessed. Although stoichiometric Ge25Sb10Se65 at. % and non-stoichiometric Ge20Sb10Se70 at. % glasses both exist within the same two-dimensional, overconstrained network, results from their fibre-drawing investigations reveal a significant difference in their resistance against crystallisation. Whereas, non-stoichiometric Ge20Sb10Se70 at. % is shown to produce stable optical fibres with promising low losses, it is found that stoichiometric Ge25Sb10Se65 at. % repeatedly crystallises into a single phase of monoclinic GeSe2. To produce a low numerical aperture (NA) step-index fibre (SIF), it is suggested that a Ge20Sb10Se70 at. % core glass is paired with a Ge20Sb10Se67S3 at. % cladding glass. Substituting 3 at. % Se for 3 at. % S in the Ge20Sb10Se70-xSx at. % series, is found to increase the glass transition temperature (Tg) by 10 °C and decrease the refractive index by 0.01. It is calculated, that for a SIF consisting of a Ge20Sb10Se70 at. % core and a Ge20Sb10Se67S3 at. % cladding, the NA would be 0.25 at 3.1 µm wavelength. Co-extruded at 267±0.1 °C, and then subsequently drawn into 200 ±5 µm diameter SIF, optical loss measurements demonstrate that MIR light can be successfully guided through a large, circular Ge20Sb10Se70 at. % core. The core-cladding ratio is found to be 95 %. Calculations using the Antoine equation are used to investigate the optimal conditions required for the bake-out of Se, S and Sb impurities prior to batching. For a high-purity Ge20Sb10Se70 at. % core glass, a distillation technique is developed using 1000 ppm wt. TeCl4 as a hydrogen getter [H] and 700 ppm wt. Al as an oxygen getter [O]. It is shown, that to successfully distil Ge-Sb-Se glass, with [H] and [O] getters, two primary challenges must be overcome. The first suggests that there must be sufficient removal of HCl(g), prior to the start of distillation, in order to avoid a vapour barrier once the silica glass distillation rig is sealed. The second advises precise temperature control, with necessary monitoring, so that there is no separation of Ge-Sb-Se material, either before or after it has distilled. Successful distillation is eventually achieved in an open system i.e. under flowing vacuum, at a temperature close to 693 °C. Optical fibre loss measurements, conducted on 18 m length of 200 ±10 µm diameter fibre, reveal that the distillation of Ge20Sb10Se70 at. % core glass with 1000 ppm wt. TeCl4 and 700 ppm wt. Al, removes the Ge-O absorption peak at 7.9 µm and significantly reduces, if not removes, all of the Se-H peaks as well. The lowest background loss is also found as 0.44 dB/m at 6.4 µm wavelength. As a preliminary investigation into the biocompatibility of Ge-Sb-Se glasses for medical applications, two in-vitro cytotoxicity test are explored viz.: a direct contact protocol with an alamarBlue® assay and an elution protocol with a neutral red assay. Due to contradictory results between Trial 1 and Trial 2, it is suggested that further work is required to confirm the cytotoxicity of etched vs. non-etched Ge-Sb-Se fibres. Overall, there has been significant progress made during this Project, towards the fabrication of high purity Ge-Sb-Se/S SIFs for use in a MIR imaging probe for early cancer diagnosis.

In a Southern state at a rural high school, leadership staff implemented phonics-based strategies with 9th grade English teachers to improve students' Lexile reading scores. The absence of formative data related to program implementation left stakeholders without a clear understanding of the influence of the phonics-based strategies. The purpose of this qualitative exploratory case study was to obtain formative information from teachers to discern the perceived influence of the phonics-based strategies on reading. Dual coding theory was used to examine teachers' perceptions of the influence of phonics-based strategies on students' motivation, fluency, and self-efficacy. Data were collected using interviews with 9 purposefully selected English teachers who taught Grade 9 students and had at least 1 year of experience using the phonics-based strategies. Data were coded in NVivo and analyzed using thematic analysis. Results indicated that phonics-based strategies were perceived to benefit students' extrinsic motivation and fluency; conversely, teachers perceived the strategies had a limited effect on students' intrinsic motivation and self-efficacy. Implementation of recommendations presented in a white paper based on these findings could result in positive social change by strengthening students' reading and promoting their academic success.