Spatial Light Modulators are used in many applications and Liquid Crystal Spatial Light Modulators are a mature technology with devices now commercially available. Over the past 3 years there has been a rapid increase in device resolution, with a decrease in pixel size. To date though, on Static Memory pixels that incorporate charge-balancing circuitry, the underlying pixel architecture has remained unchanged. This thesis presents novel "load-and-display" Static Memory pixel designs. The importance of the pixels' architectural changes is highlighted, along with design and implementation issues. The thesis also presents two more specialised pixel architectures: pixels designed for a specific application, rather than as general purpose load-and-display devices. Future trends in Liquid Crystal Spatial Light Modulators are also considered: has research and development now reached steady-state; or what impact could the designs presented in this thesis in conjunction with changes in silicon process technology have on these future trends?

The deviations in structure from that of the gas phase have been examined when the technique of liquid, crystal nuclear magnetic resonance (LCNMR) spectroscopy is applied to a series of simple silyl compounds. Both conventional vibrational corrections and an additional correction to account for the correlation between vibration and reorientation of the molecules were applied. This has indicated that the main structural differences are as a result of specific interactions between polar groups from the liquid crystal and the silicon. This interaction takes the form of an S<SUB>N</SUB>2 interaction intermediate as is found in the crystal structures of these silyl compounds. In addition, the crystal structure of two liquid crystals, 4-<I>n</I>-heptyl-4-cyanobiphenyl (7-CB) and 4-<I>n</I>-methoxy-4-cyanobiphenyl (<I>1</I>-OCB) have been determined. The molecular packing of 7-CB and the first seven members of the <I>n</I>-OCB series were then examined and found to be related to mesogenic properties of these compounds on melting.

The inherent parallelism in optics allows very powerful information processing. An electronically addressed spatial light modulator is a device which can perform the function of converting information form the electronic domain to the optical domain. A review of optical system requirements and potential spatial light modulator technologies identified the combination of Ferroelectric Liquid Crystal and Very-Large-Scale-Integration circuitry as a very powerful generic technology. The circuitry allows high levels of addressing functionality and low power requirements in the modulation permit high density arrays. The investigation of the interaction of the two parent technologies to form a useful modulator device is the basis of this study. Ferroelectric liquid crystals were identified as allowing fast switching and good light modulating characteristics. Optimisation of device structures for high optical performance was investigated, particularly cell construction, liquid crystal alignment and cell appraisal techniques. Various liquid crystal configurations were studied chiefly the Surface-Stabilised structure, but also the Soft-mode Electroclinic effect, the Distorted Helix, and Twisted Smectic. The Surface-Stabilised device structure was identified as being the most applicable for use with silicon backplanes and its fabrication parameters were optimised for good performance. Spatial light modulators were constructed and their performance evaluated. The performance of the devices constructed initially did not approach that obtained in the preliminary liquid crystal studies. Post-processing improvements to the silicon backplane, particularly planarisation, allowed tremendous improvement. Spatial light modulators were used in real-time optical systems, and their performance gauged. A novel non-coherently illuminated system, which allowed the determination of the Hadamard transform of input images, was constructed and evaluated.

Good understanding of the alignment mechanisms of liquid crystals on solid surfaces is a pre-requisite for the successful design and manufacture of high performance liquid crystal-based optoelectronic devices. Apart from selecting certain types of alignment (homogeneous or homeotropic alignment, with a specified liquid crystal pretilt) it is important to ensure liquid crystal alignment uniformity across areas of several square centimeters. Even though uniform alignment of nematic liquid crystals over large areas can be achieved relatively straightforwardly the task of aligning ferroelectric liquid crystals in their SmC* phase is formidable. Liquid crystals can be aligned by a multiplicity of methods. These include the evaporation of thin inorganic solid films, grating structures and Langmuir-Blodgett films, all of which are studied in this work with an emphasis on thin silicon monoxide (SiO) films evaporated at an oblique angle. The study concentrates at first on the analysis of the bounding surfaces found in a typical device environment: namely the transparent conductive indium-tin-oxide (ITO) electrode with a thin film of SiO which has been evaporated over it at an oblique angle. By use of a scanning electron microscope it is shown that the ITO layer exhibits roughness comparable to the usually in device configuration encountered thickness of the subsequently evaporated SiO film. Atomic force microscopy reveals columnar growth of the SiO film while the underlying morphology of the ITO layer still determines the large scale structure of the resulting surface with which the liquid crystal is in contact. Secondary ion mass spectroscopy reveals that the SiO films are oxygen rich and contain molybdenum as a contaminant. Following the appropriate preparation of the bounding surfaces and their assembly into a sandwich structure liquid crystal material is injected. If SiO alignment promoting films are used the final alignment of ferroelectric liquid crystals in their SmC* phase is found to be strongly and irreversibly dependent on the conditions during injection.

The work presented in this thesis can be divided into two main parts: a study of Cellular Automaton (CA) models of incompressible fluid flow and work on the use of Renormalisation Group (RG) methods to derive an effective viscosity for use in subgrid modelling in Large Eddy Simulation of incompressible turbulence. The derivation of hydrodynamic equations for the behaviour of CA models is reviewed in the context of classical statistical mechanics. In computer simulations of such models, velocity and density values are found by calculating averages of appropriate microscopic quantities: the effect of this averaging on noise levels in such simulations is investigated. We verify the expected results that the noise level is proportional to <i>N</i><SUP>-1/2</SUP> where <i>N</i> is the number of space cells or time-steps in the average. A new CA model, the '2D multispeed model', is developed by considering the projection of the 4D face-centred hypercubic model into 2D. Optimal collision rules are obtained and computer simulations of flow through a channel are performed, which reproduce the well-known parabolic velocity profile. Kinematic viscosity is calculated as a function of particle density from the velocity profiles and the imposed pressure gradient: the results compare favourably with those of the FHP model in terms of maximum attainable Reynolds number for a given computational effort. After briefly summarising some important aspects of turbulent fluid flow, a conditional averaging procedure is presented, designed to deal with the problems of coupling between low-wavenumber and high-wavenumber modes in the filtered Navier-Stokes equation in <i>k</i>-space. The conditional average is precisely defined in terms of the turbulent ensemble and a method of evaluation is proposed, whereby the conditional average of moments of the velocity field is related to the full-ensemble average of the same quantities, with an explicit error term representing the effect of the coupling. The application of this averaging procedure to the modelling of small-scale motion in homogeneous isotropic turbulence is explained and the derivation of an effective viscosity, due to McComb and Watt (<i>Phys. Rev. Lett. 65</i> (1990) p.3281) is outlined.

Liquid crystal spatial light modulators (LC SLMs) are used in a variety of applications including information display, optical computing and information processing, holographic data storage and adaptive optics. Only in displays, however, have they achieved widespread use outside the research laboratory. Part of the reason for this is the comparatively low optical quality of most LC modulators currently available. This thesis explores methods which can be used to characterize and enhance these devices: particularly those intended for use in non-display applications where output wavefront quality, and spatial device uniformity, can be critical. One key device parameter to be determined is the value and uniformity of the cell gap which defines the thickness of the LC layer. Surface profile measurement is also important for assessing, for example, the optical quality of reflective VLSI pixel arrays. In addition, characterization of LC response for a given input drive signal is often needed to allow prediction of SLM performance in a particular optical system. The development of methods for accurate determination of LC cell gaps is described. Broadband and multiple-wavelength interferometry are used to provide the large unambiguous measurement range necessary for absolute measurement of these micron-scale distances. One method is based on the technique of phase-shifting interferometry and allows the spatial variations to be mapped relatively quickly from a small number of interferograms acquired at different wavelengths. Techniques for reducing systematic measurement errors are discussed and demonstrated both through numerical simulation and experiment. A novel white-light interferometer configuration is also described, based on spectral analysis of white light interferograms using an imaging stationary Fourier transform spectrometer. It is shown that this configuration permits real-time visualization of spatial variations in interferometer path difference, as well as giving unambiguous depth measurements with nanometre resolution. Applications to surface profiling and to cell gap determination are discussed and experimental surface measurement results given.

Experiments have been performed on the flow generated after the breaking of laboratory-generated water waves. Digital Particle Image Velocimetry (DPIV) was employed to make flow-field measurements in the post-breaking region of both spilling and plunging breakers, for a range of times close to breaking. The development of the technique in order to study the temporal evolution of the flow with high resolution CCD cameras is outlined. The visual record generated by PIV is presented in the form of a large set of vorticity and velocity maps. This information is used to describe the flow and its evolution over time. The raw data is then further processed in order to demonstrate the effectiveness of PIV in measuring complex turbulent characteristics. Energy and velocity profiles, temporal decay of turbulent kinetic energy and power spectra are calculated and the results compared with other experimental, numerical and theoretical work. Similarities and differences are considered and explanations offered.

This work describes an experimentally based investigation into the use of spatial light modulators in coherent optical processing systems. The initial stages of the work revolve around designing a VanderLugt type optical correlator based upon two spatial light modulator devices. The spatial light modulators employed in the design are 256 x 256 pixel displays previously designed within the research group. We present the design specification and projected optical performance for a coherent optical correlator designed around these modulators. Alongside the development of the optical processing system, we present an investigation into possible processing algorithms and applications of the system. We investigate optical correlation and its application in morphological image processing. This, together with the use of stereo imagery and novel range analysis methods, provides the basis for an optical processing strategy to be implemented using the optical processor. Simulation results are presented showing the performance benefits provided by range analysis over direct correlation for target recognition, specifically for a group of targets similar to appearance to road signs. Initial optical correlator results are presented, showing significant shortcomings in the performance of the optical system. An experimental process of analysis reveals the primary source of signal degradation to be caused by poor performance of the spatial light modulators. This forces a change of track in the flow of the project towards a detailed investigation of the display device properties.

In order to gain a deeper understanding of the relationship between molecular structure and liquid crystal properties, accurate data is required on single molecule properties of mesogenic fragments and molecules. This thesis applies a pseudopotential plane wave total energy method to calculate molecular properties of prototypical mesogenic fragments and the molecule 4-n-pentyl-4'-cyanobiphenyl (5CB) from first principles. Optimised molecular structures, vibrational properties and torsional potentials are determined and found to compare well with experimental observations and other <I>ab initio</I> investigations. A study is made of the transferability of torsional potentials between mesogenic fragments and 5CB. Also investigated is the conformation-dependence of dipole and quadrupole moments. The strength of the coupling is found to depend sensitively on the molecular structure and the conformation-dependence of quadrupole moments is found to significantly influence inter-molecular interactions. Finally, by combing first principles calculations with an empirical mean field approximation, conformational distributions of the alkyl tail in 5CB are examined.

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