Since the demonstration of Extraordinary Optical Transmission (EOT) in sub-wavelength aperture arrays, first at optical then at terahertz (THz) frequencies, the role of Surface Plasmon Polaritons (SPPs) in this phenomenon has been under investigation. By studying the interaction between THz radiation and free standing metal foils, which contain periodic arrays of apertures, this thesis explores the interaction between rectangular waveguided modes controlled by aperture dimensions and SPP modes defined by aperture periodicity. Fabrication of a free standing metal foil perforated by micron scale 5:1 aspect ratio rectangular holes with varied array spacings is performed by photolithography and electroplating. Such free standing metal foils are shown to demonstrate EOT at THz frequencies when studied by terahertz time-domain spectroscopy (THz-TDS). Results obtained by the systematic variation of aperture size and lattice spacing are presented, accompanied by finite-difference time-domain (FDTD) simulation data. The changing aperture array dimensions allow for the isolation of the different resonant modes present in the EOT phenomena. Further exploitation of the interaction between the two resonant modes is provided by altering the incident angle between the free standing metal aperture array and the THz field. The high frequency resolution provided by THz Vector Network Analyser measurements allows for small changes in transmission spectra to be observed as the resonant modes are brought into close proximity. The removal of a fixed periodic spacing between the sub-wavelength apertures perforating the metal foil removes a necessary component of SPP excitation. The design of an array of aperiodic sub wavelength apertures is presented. This array demonstrates EOT in the absence of SPPs. Furthermore, SPPs induced by the periodic x-axis aperture spacing, and controlled by THz field incidence angle, are used to extinguish the sharp transmission resonance produced by the sub-wavelength apertures. To this author’s knowledge this is the first reporting of resonant transmission extinguished by SPP excitation and manipulation.

Ground based telescopes suffer from degraded resolution due to aberrations induced by the atmosphere which prevent them from reaching the diffraction limit. Adaptive Optics (AO) is a technology which corrects for this effect in real-time, restoring the resolution of a telescope. However, it only corrects for a very narrow field of view (FOV) around the guide source. Tomographic AO uses multiple guide sources to increase the size of the corrected FOV, however, these forms of AO are affected by the vertical distribution of turbulence in the atmosphere (turbulence profile). This thesis presents work to develop turbulence profiling instruments for daytime astronomy and improve centroiding techniques for correlating wavefront sensors (WFS) which are used in slope based turbulence profiling instruments. The development of centroiding techniques for use on extended objects is based on cross-correlation techniques. Two methods are presented, one for optimising centroiding parameters on cross-correlation images and another for improving the signal to noise in cross-correlation images created from images with large relative shifts by using supersized reference images. Choosing optimal centroiding parameters for correlating WFSs is demonstrated in simulation, optimising a windowed, thresholded center of mass. The creation and use of supersized reference images is also demonstrated in simulation, where they are created from WFS data and shown to drastically improve the accuracy of centroiding for centroiding extended objects which have continuous structure across the whole field. So-SLODAR (solar-slope detection and ranging) was developed as a slope based instrument for measuring the turbulence profile on the Swedish Solar Telescope (SST), La Palma. The technique is based on SLODAR, with developments to take advantage of the continuous structure of the solar surface offering multiple guide sources. A full description of the technique and its data reduction is presented, along with the first results from on-sky tests on the SST.

Plasmonic metamaterials have customized linear and nonlinear optical properties. This thesis investigates the properties of an anisotropic plasmonic metamaterial, consisting of aligned, interacting gold nanorods, to perform ultrafast light modulation, exploiting the intrinsic Kerr nonlinearity of gold. This e ect is based on an illumination-intensity-dependent change in the gold's permittivity, which takes place on ultrafast timescales and induces the intensity-dependent change of the metamaterial's re ection and transmission. A comprehensive theoretical and numerical analysis of the linear and nonlinear response of various con gurations of the metamaterial is performed and compared to experimental results. A new family of hyperbolic waveguided modes above the e ective plasma frequency, enabled by spatial dispersion, is identi ed. The strong nonlinear response and the dynamic modulation capabilities associated with the excitation of the waveguided modes is investigated. The presence of strong electron temperature gradients in the nanorods induced by a control light is shown to determine a stronger nonlinear modulation and to in uence the dynamic response, leading to subpicosecond time recovery components of the nonlinearity. Weak and strong coupling between molecular excitons and the metamaterial's modes can be achieved using core-shell nanorod geometries. The coherent interaction of molecular J-aggregates with coreshell nanorod arrays is analyzed in both the weak and strong coupling regimes. Subpicosecond components of the modulation are determined in the strong coupling conditions. The design of the optical response of the gold nanorod and core-shell metamaterials is studied through the near- to mid- Infrared, key spectral regions for molecular ngerprinting in chemical sensing and absorption spectroscopy. The applicability limits of the analytic approaches using the quasi-static and e ective medium approximations is tested. The results show great potential of the plasmonic nanorod metamaterial for ultrafast nonlinear optics in free-space and integrated applications, in a broad spectral range.

Fibre-optic components and systems are used in a wide variety of industrial, medical and communication applications and can be found in use everywhere in the modern world, from the bottom of the ocean to satellites in orbit. The field of fibre optics has seen rapid growth in the past few decades to become an essential enabling technology. However, much more work is needed to develop components and systems that can work at wavelengths in the short-wavelength infrared (SWIR)/mid-IR part of the spectrum (defined in this work as 1.5 – 4.5).

No description available.

No description available.

This thesis reports the creation and trapping of 87RbCs molecules in the absolute ground state with a temperature of 1 uK. We build a tunable narrow-linewidth laser system at 1550 nm and 980 nm, using a single high-finesse optical cavity as a reference for both colours. We use fibre-coupled electro-optic modulators to continuously tune both lasers. These allow a novel measurement of the free spectral range of the cavity to better than 1 part in 10^6. We perform one- and two-photon spectroscopy on 87RbCs Feshbach molecules and identify a suitable intermediate state for transfer to the molecular ground state. We measure the electric dipole moment of the molecular ground state as 1.225(3)(8) D, and demonstrate the highest lab-frame dipole moment of any ultracold molecular system at the time of measurement. We transfer the molecules to the electronic, rovibrational and hyperfine ground state using stimulated Raman adiabatic passage, with 88% efficiency. We measure the transition strengths and excited state linewidth for this transfer route. We develop a model for the transfer which includes the effect of laser linewidth, and find excellent agreement with experimental data. The molecular sample is trapped in an optical dipole potential, and has a lifetime of 0.89(6) s. We reference the STIRAP lasers to a novel design of frequency comb which uses difference frequency generation to cancel the carrier-envelope offset. We use this to measure the binding energy of the molecules as h x 114 268 135.24(4)(3) MHz. To our knowledge, this is the most precise determination of the dissociation energy of a molecule to date. Finally, we report progress toward loading the molecules into a 1D optical lattice at 1064 nm. We develop the tools and methods to characterise a lattice, and demonstrate trapping of Feshbach molecules in both a 1D optical lattice and a harmonic optical potential at 1064 nm.

This thesis investigates the use of field and satellite data for crop area estimation in the northern part of the West Bank, Palestine. The satellite data were obtained by the SPOT HRV on 19 May 1994. The satellite data were geometrically corrected to the Palestine Grid using 1: 50,000 Israeli topographic maps. The study investigated the ability of SPOT HRV data to produce accurate crop area estimation of the northern part of the West Bank that is characterised with small field sizes and complex physical environment. A land cover classification scheme appropriate to the study area was designed. Twenty-three land cover classes were produced from the SPOT HRV classification. Land cover classes were developed to produce thematic land use classes. The classification accuracy obtained from SPOT HRV image classification was 81%. Classification results were assessed by using the known land use information obtained from the field during the training stage and the field sampling survey. The study area was divided into five strata and the field survey was conducted by applying a stratified random sampling methodology. Seventy three 1 km(^2) sample units were randomly chosen and surveyed by the author using maps, aerial photographs, satellite photographs, a questionnaire, camera photographs, and sketches. The field area measurements were taken and the final hectarage estimates were obtained for each crop type. The SPOT HRV and the field data were combined in regression analysis using a double sampling method and a hectarage estimate was produced for each crop in the study area. The results obtained showed that the regression estimator was more efficient than the field estimator and a gain in precision was achieved. The results were analysed on stratum and crop type basis. Remote sensing and thematic agricultural perspectives were used in the analysis. Results of the study suggest that it is possible to improve image classification accuracy by using better spatial and spectral resolution imagery and the integration of remote sensing data with agricultural data using the Geographical Information Systems (GIS).

Quantum cascade lasers (QCLs) are capable of high power, tunable wavelength and single mode emission at room temperature in the mid-infrared wavelength region. These capabilities make them perfect light sources for laser based gas spectroscopy. The work described in this thesis focuses on development of QCLs suitable for selective gas sensing applications. The thesis starts with the description of different changes to the QCL active region design. These changes were studied in order to improve laser performance while keeping the emission wavelength fixed. The proposed modifications were performed on short mid-infrared wavelength (lambda=3-4um) quantum cascade lasers based on InGaAs/AlAsSb and InAs/AlSb material systems. The focus of this work is then moved to the description of a single mode quantum cascade laser with a third order unilateral grating. The previously unreported grating architecture that was used to achieve distributed feedback (DFB) in a QCL, as well as grating design and laser characterization are detailed in Chapter \ref{chap:uni}. The reported laser generates single mode emission with 30 dB side mode suppression ratio and a linewidth of 0.4cm^(-1). The simplified fabrication process for a third order DFB grating is developed for lambda=3.3-3.6um emission wavelength. A different approach to achieve single mode emission in a QCL is described in Chapter 6. An external cavity QCL setup combined with the Fabry-Perot (FP) reflector is reported for the first time. The FP reflector is used to provide selective feedback that is controlled by the separation distance between two FP reflector mirrors. This external cavity arrangement allows generation of a wide spectral range and the rapid wavelength tuning capability. Finally, the thesis is concluded with sensitive gas detection experiments. The direct absorption technique is utilized to demonstrate the 160ppmv detection of methane with the ro-vibrational absorption line located at lambda=3.3um and 1ppmv detection of nitric oxide with the absorption line located at lambda=5.3um. The experiments were performed using single mode lasers that were designed and fabricated in Sheffield.

Engineering process design for applications that use computationally intensive nonlinear dynamical systems can be expensive in time and resources. The presented work reviews the concept of a meta-model as a way to improve the efficiency of this process. The proposed meta-model will have a computational advantage in implementation over the computationally intensive model therefore reducing the time and resources required to design an engineering process. This work proposes to meta-model a computationally intensive nonlinear dynamical system using reduced-order linear parameter varying system modelling approach with local linear models in velocity based linearization form. The parameters of the linear time-varying meta-model are blended using Gaussian Processes regression models. The meta-model structure is transparent and relates directly to the dynamics of the computationally intensive model while the velocity-based local linear models faithfully reproduce the original system dynamics anywhere in the operating space of the system. The non-parametric blending of the meta-model local linear models by Gaussian Processes regression models is ideal to deal with data sparsity and will provide uncertainty information about the meta-model predictions. The proposed meta-model structure has been applied to second-order nonlinear dynamical systems, a small sized nonlinear transmission line model, medium sized fluid dynamics problem and the computationally intensive nonlinear transmission line model of order 5000.