This study successfully demonstrates the electrical control of the surface wettability of liquid crystal and polymer composite film. The application of external voltages significantly affects the surface wettability of the film. This study uses atomic force microscopy to quantitatively characterize the fundamental mechanism responsible for the structurally driven changes in surface properties at various applied voltages. The surface wettability transitions of the film are electrically driven, as shown by reorganized liquid crystal molecules. Measurements of the voltage-dependent surface wettability of the composite film suggest novel approaches to supporting control applications of future electro-optical nanotechnology devices, including liquid lenses, windshields and displays.

This thesis use laser diode, lens, grating, and mirrors to composite the external cavity system to retrieve the thickness of the liquid crystal and its characteristics. This way is different to the traditional way of measure. It has good accuracy on the vertical resolution and the vertical resolution can reach to 0.3£gm. At the same time, it can develop the high quality of horizontal resolution. On the basis of the correlation between the cavity length and the wavelength of the semiconductor laser, the system is capable of developing high horizontal resolution of accurate liquid crystal measurements. The horizontal resolution can reach to 40£gm. Furthermore, by adding bias on liquid crystal through this system, it expanded more understandings on the influences of bias and induced electric field of the electrodes to the tilting angle of the liquid crystal.

Thesis (Ph.D.)--Brown University, 2008. / Vita. Advisor : Gregory P. Crawford. Includes bibliographical references (leaves 149-174).

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Photonic bandgap materials are periodic structures that exclude electromagnetic field propagation over frequency intervals known as bandgaps. These materials exhibit remarkable wave dispersion and have found use in many applications that require control over dynamic electromagnetic fields, as their properties can be tailored by design. The two principal objectives of this thesis are the development of a liquid crystal-based microwave photonic bandgap device whose bandgap could be tuned during operation and the design and implementation of a spectral transmission-line modeling method for band structure calculations. The description of computational methods comprises an overview of the implemented numerical routines, a derivation of the spectral properties of the transmission-line modeling method in periodic domains, and the development of an efficient sparse matrix eigenvalue algorithm that formed the basis of the spectral transmission-line modeling method. The discussion of experimental methods considers the use of liquid crystals in microwave applications and details the design and fabrication of several devices. These include a series of modified twisted nematic cells that were used to evaluate liquid crystal alignment and switching, a patch resonator that was used to measure liquid crystal permittivity, and the liquid crystal photonic bandgap device itself. Numerical experiments showed that the spectral transmission-line modeling method is accurate and substantially faster and less memory intensive than the reference plane wave method for problems of high dielectric contrast or rapidly varying spatial detail. Physical experiments successfully realized a microwave photonic bandgap structure whose bandgap could be continuously tuned with a bias voltage. The very good agreement between simulated and measured results validate the computational and experimental methods used, particularly the resonance-based technique for permittivity measurement. This work's results may be applied to many applications, including microwave filters, negative group velocity/negative refraction materials, and microwave permittivity measurement of liquid crystals.

Self-assembly of nanorods (NRs) enhanced by functionalization with liquid crystals (LC) ligands has been demonstrated. First, CTAB (cetyltrimethylammonium bromide) coated gold NRs were prepared in water through a modified one-step seed growth process. The hydrophilic GNRs were then converted into hydrophobic NRs employing a surface modification process using liquid crystalline organosilanes. The functionalized GNRs were characterized by TEM (transmission electron microscopy) and SAXS (small angle X-ray scattering) to investigate the packing mode of the GNRs. The results propose models of the assembly of the GNRs depending on nature and connectivity of the attached liquid crystal molecules. Furthermore, a macroscopic orientation of the GNRs doped in LC was achieved via an alignment technique of the liquid crystal host. SAXS analysis of the doped DLC indicated modification of lattice parameters due to the insertion of the DLC-GNRs, which resulted in an enhancement of the charge carrier mobility.

Photonic bandgap materials are periodic structures that exclude electromagnetic field propagation over frequency intervals known as bandgaps. These materials exhibit remarkable wave dispersion and have found use in many applications that require control over dynamic electromagnetic fields, as their properties can be tailored by design. The two principal objectives of this thesis are the development of a liquid crystal-based microwave photonic bandgap device whose bandgap could be tuned during operation and the design and implementation of a spectral transmission-line modeling method for band structure calculations. The description of computational methods comprises an overview of the implemented numerical routines, a derivation of the spectral properties of the transmission-line modeling method in periodic domains, and the development of an efficient sparse matrix eigenvalue algorithm that formed the basis of the spectral transmission-line modeling method. The discussion of experimental methods considers the use of liquid crystals in microwave applications and details the design and fabrication of several devices. These include a series of modified twisted nematic cells that were used to evaluate liquid crystal alignment and switching, a patch resonator that was used to measure liquid crystal permittivity, and the liquid crystal photonic bandgap device itself. Numerical experiments showed that the spectral transmission-line modeling method is accurate and substantially faster and less memory intensive than the reference plane wave method for problems of high dielectric contrast or rapidly varying spatial detail. Physical experiments successfully realized a microwave photonic bandgap structure whose bandgap could be continuously tuned with a bias voltage. The very good agreement between simulated and measured results validate the computational and experimental methods used, particularly the resonance-based technique for permittivity measurement. This work's results may be applied to many applications, including microwave filters, negative group velocity/negative refraction materials, and microwave permittivity measurement of liquid crystals.

Coherent optical data processing is recognised, for many applications, as a viable alternative to digital electronic signal processing; the case for using coherent optics is particularly strong when the data to be processed is two dimensional in nature. It has long been accpeted that, in order for coherent optical processing to achieve its full performance potential, two dimensional spatial light modulators - capable of operating in real time - are essential at both the object plane (where the data is input to the system) and the Fourier plane (where the operation carried out on the data is determined). Most previous research in the field of spatial modulators has concentrated on optically addressed devices for use in the object plane. This thesis describes a prototype liquid crystal over silicon spatial light modulator built to test the feasibility of using such devices in a coherent optical processor. Optically, the device operates as a binary amplitude modulator, consisting of a square array of 16x16 pixels, each of size 100x100 m^2 and located at 200m centres. The integrated circuit is designed for a 6m wafer fabrication process. Each pixel of the IC contains a static memory element (which stores a digital logic voltage corresponding to the optical state of that pixel) and provides a stable square wave voltage signal to drive the liquid crystal layer. The component parts of the spatial light modulator are tested individually: the liquid crystal, in test cells, for contrast and switching speed; the IC for electrical performance and optical (flatness) characteristics. The effect of pixellation on optical performance is investigated. The performance of live devices is demonstrated. The results indicate the feasibility of using such a device as a binary amplitude spatial light modulator.

Copies of author's previously published articles inserted. / Bibliography: p. 119-129. / xvi, 129, [58] p. : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis investigated the suitability of liquid crystal spatial light modulators as versatile computer controlled optical elements. The modulation characteristics were determined empirically and experimentally, and their performance as phase modulators tested in the two diverse applications of computer generated holography and phase aberration correction. Commercial liquid crystal panels from a video projector were used, chosen because of low cost, high resolution, computer controlled input, reconfigurability and ready availability. The panels were found to be more suited to amplitude than to phase modulation. Results show that the devices are versatile enough to be adapted to the two very different applications. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 1998