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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

Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 1998. / Copies of author's previously published articles inserted. Bibliography: p. 119-129.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references (leaves 87). Also available in electronic version. Access restricted to campus users.

Thesis (Ph.D.)--Kent State University, 2005. / Title from PDF t.p. (viewed Sept. 14, 2006). Advisor: Philip J. Bos. Keywords: liquid crystal; diffractive optical element; optical phased array; spatial light modulator; high resolution wavefront control; aberration correction. Includes bibliographical references (p. 206-213).

In this PhD Thesis I present some methods for characterizing PA-LCoS microdisplays. It is useful to fully characterize this type of devices for evaluating its performance required in different applications. We have tested its validity in different applications such as diffractive optics elements (DOEs). Finally we apply these microdisplays in a full holographic data storage scheme using a photopolymer as holographic recording medium. We evaluate the capability of PVA/AA photopolymer for this holographic data storage system that incorporates as a novelty a convergent correlator geometry.

Dissertation (Ph.D.)--Auburn University, / Abstract. Vita. Includes bibliographic references.

Solar energy is widely used for electricity generation, heating systems, and indoor environment daytime illumination. Indeed, large amounts of Sunlight energy remain insufficiently used. In this work, we aim at employing sunlight for data transmission as another option for wireless communications. Being emitted by an uncontrollable source, taming the Sunlight is a challenging task that requires appropriate technolo- gies to manipulate incident light. Throughout this thesis, we first review switchable glass technologies and investigate their potential use for light modulation. Liquid Crystal Devices (LCD) have adequate response time and contrast characteristics for such an application. In this regard, we design a novel Dual-cell Liquid Crystal Shutter (DLS) by stacking two Liquid Crystal cells that operate in opposite manners, and we build our Sunlight modulator with an array of DLSs. Then, we adopt Time Division Multiplexing and polarization-based modulation to boost the data rate and eliminate the flickering effect. In addition, we provide mathematical modeling of the system and study its performance in terms of communication and energy consumption. Finally, we introduce some numerical results to examine the impact of multiple parameters on the system’s performance and compare it with state-of-the-art, which showed that our system features higher data rates and extended link ranges.

Liquid crystal (LC)-based adaptive optics are important for information processing, optical interconnections, photonics, integrated optics, and optical communications due to their tunable optical properties. In this dissertation, we describe novel liquid crystal photonic devices and their fabrication methods. The devices presented include inhomogeneous polymer-dispersed liquid crystal (PDLC), polymer network liquid crystals (PNLC) and phase-separated composite film (PSCOF). Liquid crystal/polymer composites could exist in different forms depending on the fabrication conditions. In Chap. 3, we demonstrate a novel nanoscale PDLC device that has inhomogeneous droplet size distribution. In such a PDLC, the inhomogeneous droplet size distribution is obtained by exposing the LC/monomer with a non-uniform ultraviolet (UV) light. An electrically tunable-efficiency Fresnel lens is devised for the first time using nanoscale PDLC. The tunable Fresnel lens is very desirable to eliminate the need of external spatial light modulator. Different gradient profiles are obtained by using different photomasks. The nanoscale LC droplets are randomly distributed within the polymer matrix, so that the devices are polarization independent and exhibit a fast response time. Because of the small droplet sizes, the operating voltage is higher than 100 Vrms. To lower the driving voltage, in Chap. 2 and Chap. 3, we have investigated a polymer-network liquid crystal (PNLC) using a rod-like monomer structure. Since the monomer concentration is only about 5%, the operating voltage is below 10 Vrms. The PNLC devices are polarization dependent. To overcome this shortcoming, stacking two cells with orthogonal alignment directions is a possibility. In Chap. 3, another approach to lower the operating voltage is to use phase-separated composite film (PSCOF) where the LC and polymer are separated completely to form two layers. Without multi-domain formed in the LC cell, PSCOF is free from light scattering. Using PNLC and PSCOF, we also demonstrated LC blazed grating and Fresnel lens. The diffraction efficiency of these devices is continuously controlled by the electric field. Besides Fresnel lens, another critical need for imaging and display is to develop a system with continuously tunable focal length. A conventional zooming system controls the lens distance by mechanical motion along the optical axis. This mechanical zooming system is bulky and power hungry. To overcome the bulkiness, in Chap. 4 we developed an electrically tunable-focus flat LC spherical lens which consists of a spherical electrode imbedded in the top flat substrates while a planar electrode on the bottom substrate. The electric field from the spherical and planar electrodes induces a centrosymmetric gradient refractive index distribution within the LC layer which, in turn, causes the focusing effect. The focal length is tunable by the applied voltage. A tunable range from 0.6 m to infinity is achieved. Microlens array is an attractive device for optical communications and projection displays. In Chap. 5, we describe a LC microlens array whose focal length can be switched from positive to negative or vise versa by the applied voltage. The top spherical electrode glass substrate is flattened with a polymer layer. The top convex substrate and LC layer work together like a zoom lens. By tuning the refractive index profile of the LC layer, the focal length of the microlens array can be switched from positive to negative or vise versa. The tunable LC microlens array would be a great replacement of a conventional microlens array which can be moved by mechanical elements. The fast response time feature of our LC microlens array will be very helpful in developing 3-D animated images. A special feature for LC/polymer composites is light scattering. The concept is analogous to the light scattering of clouds which consist of water droplets. In Chap. 6, we demonstrate polymer network liquid crystals for switchable polarizers and optical shutters. The PNLC can present anisotropic or isotropic light scattering behavior depending on the fabrication methods. The use of dual-frequency liquid crystal and special driving scheme leads to a sub-millisecond response time. The applications for display, light shutters, and switchable windows are emphasized. Although polymer networks help to reduce liquid crystal response time, they tend to scatter light. In Chap. 7, for the first time, we demonstrate a fast-response and scattering-free homogeneously-aligned PNLC light modulator. Light scattering in the near-infrared region is suppressed by optimizing the polymer concentration such that the network domain sizes are smaller than the wavelength. As a result, the PNLC response time is ~300X faster than that of a pure LC mixture except that the threshold voltage is increased by ~25X. The PNLC cell also holds promise for mid and long infrared applications where response time is a critical issue.

The vectorial nature (polarization) of light plays a significant role in light-matter interaction that leads to a variety of optical devices. The polarization property of light has been exploited in imaging, metrology, data storage, optical communication and also extended to biological studies. Most of the past studies fully explored and dealt with the conventional polarization state of light that has spatially symmetric electrical field geometry such as linear and circular polarization. Recently, researchers have been attracted to light whose electric field vector varies in space, the so-called optical vector vortex beam (VVB). Such light is expected to further enhance and improve the efficiency of optical systems. For instance, a radially polarized light under focusing condition is capable of a tighter focus more than the general optical beams with a uniform polarization structure, which improves the resolution of the imaging system [1]. Interaction of ultrafast laser pulses with matter leads to numerous applications in material processing and biology for imaging and generation of microfluidic systems. A femtosecond pulse, with very high intensities of (10^{12} - 10^{13} W/cm^2), has the potential to trigger a phenomenon of optical breakdown at the surface and therefore induce permanent material modification. With such high intensities and taking into account the fact that most materials possess large bandgap, the interaction is completely nonlinear in nature, and the target material can be modified locally upon the surface and even further in bulk. The phenomenon of optical breakdown can be further investigated by studying the nonlinear absorption. Properties like very short pulse duration and the high irradiance of ultrashort laser pulse lead to more precise results during the laser ablation process over the long pulsed laser. The duration of femtosecond laser pulse provides a high resolution for material processing because of the significant low heat-affected zone (HAZ) beyond the desired interaction spot generated upon irradiating the material. Under certain condition, the interaction of intense ultrashort light pulses with the material gives rise to the generation of periodic surface structures with a sub-micron periodicity, i.e., much smaller than the laser wavelength. The self-oriented periodic surface structures generated by irradiating the material with multiple femtosecond laser pulses results in improving the functionality of the material's surface such as controlling wettability, improving thin film adhesion, and minimizing friction losses in automobile engines, consequently, influences positively on many implementations. In this work, we introduced a new method to study complex polarization states of light by imprinting them on a solid surface in the form of periodic nano-structures. Micro/Nanostructuring of diamond by ultrafast pulses is of extreme importance because of its potential applications in photonics and other related fields. We investigated periodic surface structures usually known as laser-induced periodic surface structures (LIPSS) formed by Gaussian beam as well as with structured light carrying orbital angular momentum (OAM), generated by a birefringent optical device called a q-plate (QP). We generated conventional nano-structures on diamond surface using linearly and circularly polarized Gaussian lights at different number of pulses and variable pulse energies. In addition, imprinting the complex polarization state of different orders of optical vector vortex beams on a solid surface was fulfilled in the form of periodic structures oriented parallel to the local electric field of optical light. We also produced a variety of unconventional surface structures by superimposing a Gaussian beam with a vector vortex beam or by superposition of different order vector vortex beams. This thesis is divided into five chapters, giving a brief description about laser-matter interaction, underlying the unique characterization of femtosecond laser over the longer pulse laser and mechanisms of material ablation under the irradiation of fs laser pulse. This chapter also presents some earlier studies reported in formation of (LIPSS) fabricated on diamond with Gaussian. The second chapter explains the properties of twisted light possessing orbital angular momentum in its wavefront, a few techniques used for OAM generation including a full explanation of the q-plate from the fabrication to the function of the q-plate, and the tool utilized to represent the polarization state of light (SoP), a Poincar'e sphere. Finally, the experimental details and results are discussed in the third and fourth chapters, respectively, following with a conclusion chapter that briefly summarizes the thesis and some potential application of our findings.