Autostereoscopic 2D/3D (two-dimension/three-dimension) switchable display has been attracting great interest in research and practical applications for several years. Among different autostereoscopic solutions, direction-multiplexed 3D displays based on microlens array or parallax barrier are viewed as the most promising candidates, due to their compatibility with conventional 2D display technologies. These 2D/3D switchable display system designs rely on fast switching display panels and photonics devices, including adaptive focus microlens array and switchable slit array. Polymer-stabilized blue phase liquid crystal (PS-BPLC) material provides a possible solution to meet the aforementioned fast response time requirement. However, present display and photonic devices based on blue phase liquid crystals suffer from several drawbacks, such as low contrast ratio, relatively large hysteresis and short lifetime. In this dissertation, we investigate the material properties of PS-BPLC so as to improve the performance of PS-BPLC devices. Then we propose several PS-BPLC devices for the autostereoscopic 2D/3D switchable display system designs. In the first part we evaluate the optical rotatory power (ORP) of blue phase liquid crystal, which is proven to be the primary reason for causing the low contrast ratio of PS-BPLC display systems. Those material parameters affecting the ORP of PS-BPLC are investigated and an empirical equation is proposed to calculate the polarization rotation angle in a PS-BPLC cell. Then several optical compensation methods are proposed to compensate the impact of ORP and to improve the contrast ratio of a display system. The pros and cons of each solution are discussed accordingly. In the second part, we propose two adaptive focus microlens array structures and a high efficiency switchable slit array based on the PS-BPLC materials. By optimizing the design parameters, these devices can be applied to the 2D/3D switchable display systems. In the last section, we focus on another factor that affects the performance and lifetime of PS-BPLC devices and systems: the UV exposure condition. The impact of UV exposure wavelength, dosage, uniformity, and photo-initiator are investigated. We demonstrate that by optimizing the UV exposure condition, we can reduce the hysteresis of PS-BPLC and improve its long term stability.

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Thin-film-transistor (TFT) liquid crystal display (LCD) has been widely used in smartphones, pads, laptops, computer monitors, and large screen televisions, just to name a few. A great deal of effort has been delved into wide viewing angle, high resolution, low power consumption, and vivid color. However, relatively slow response time and low transmittance remain as technical challenges. To improve response time, several approaches have been developed, such as low viscosity liquid crystals, overdrive and undershoot voltage schemes, thin cell gap with a high birefringence liquid crystal, and elevated temperature operation. The state-of-the-art gray-to-gray response time of a nematic LC device is about 5 ms, which is still not fast enough to suppress the motion picture image blur. On the other hand, the LCD panel's transmittance is determined by the backlight, polarizers, TFT aperture ratio, LC transmittance, and color filters. Recently, a fringe-field-switching mode using a negative dielectric anisotropy (Δε) LC (n-FFS) has been demonstrated, showing high transmittance (98%), single gamma curve, and cell gap insensitivity. It has potential to replace the commonly used p-FFS (FFS using positive Δε LC) for mobile displays. With the urgent need of submillisecond response time for enabling color sequential displays, polymer-stabilized blue phase liquid crystal (PS-BPLC) has become an increasingly important technology trend for information display and photonic applications. BPLCs exhibit several attractive features, such as reasonably wide temperature range, submillisecond gray-to-gray response time, no need for alignment layer, optically isotropic voltage-off state, and large cell gap tolerance. However, some bottlenecks such as high operation voltage, hysteresis, residual birefringence, and slow charging issue due to the large capacitance, remain to be overcome before their widespread applications can be realized. The material system of PS-BPLC, including nematic LC host, chiral dopant, and polymer network, are discussed in detail. Each component plays an essential role affecting the electro-optic properties and the stability of PS-BPLC. In a PS-BPLC system, in order to lower the operation voltage the host LC usually has a very large dielectric anisotropy (Δε > 100), which is one order of magnitude larger than that of a nematic LC. Such a large Δε not only leads to high viscosity but also results in a large capacitance. High viscosity slows down the device fabrication process and increases device response time. On the other hand, large capacitance causes slow charging time to each pixel and limits the frame rate. To reduce viscosity, we discovered that by adding a small amount (~6%) of diluters, the response time of the PS-BPLC is reduced by 2X-3X while keeping the Kerr constant more or less unchanged. Besides, several advanced PS-BPLC materials and devices have been demonstrated. By using a large Δε BPLC, we have successfully reduced the voltage to <10V while maintaining submillisecond response time. Finally we demonstrated an electric fieldindeced monodomain PS-BPLC, which enables video-rate reflective display with vivid colors. The highly selective reflection in polarization makes it promising for photonics application. Besides displays in the visible spectral region, LC materials are also very useful electro-optic media for near infrared and mid-wavelength infrared (MWIR) devices. However, large absorption has impeded the widespread application in the MWIR region. With delicate molecular design strategy, we balanced the absorption and liquid crystal phase stability, and proposed a fluoro-terphenyl compound with low absorption in both MWIR and near IR regions. This compound serves as an important first example for future development of low-loss MWIR liquid crystals, which would further expand the application of LCs for amplitude and/or phase modulation in MWIR region.

A simple method for increasing the stable temperature range of the liquid crystalline blue phase is demonstrated, by mixing a non-mesogenic polymer of low molecular weight into the blue phase material. In a mixture of cholesteryl benzoate and cholesteryl nonanoate the addition of polystyrene increased the stable blue phase range from 0.5K to 12K. This was measured strictly on heating from the chiral nematic phase through the blue phase in order to minimise non-equilibrium effects, and is one of the largest ranges so measured. The stability range can be closely tuned by changing the polymer concentration and molecular weight. The maximum range found by adding a particular compound seems only to depend on its saturation point in the liquid crystal, and the dependence of the range on concentration is non-linear. These features were explained by a numerical model of a blue phase unit cell incorporating the mean field Flory-Huggins and Maier-Saupe theories where the polymer could fill the high energy defect regions. Two of the oligomers which are shown to stabilise the blue phase are fluorescent, at 450nm and 500nm respectively, and it is proposed that tests on these mixtures could reveal photonic effects caused by the concentration of the fluorophores in the blue phase defect regions. The twist-grain boundary (TGB) phase is present in mixtures of cholesteryl oleyl carbonate and cholesteryl nonanoate over a range of up to 0.3K. The addition of polystyrene has no effect on the stability of the TGB phase. Conventional, in situ UV-initiated polymer stabilisation does not appear to stabilise the TGB phase, but is capable of stabilising over at least 30K the micron-size filaments which appear in the TGB phase when it is heated from the smectic phase in a cell with homeotropic alignment. Some notes are made on the causes and structure of this filament texture, and it is observed that the filaments tend to grow with a characteristic curvature. It is shown theoretically that the correct material could stabilise the TGB phase similarly to the polymers in the blue phase, by extending the previous model to include the Kobayashi-McMillan theory of smectic ordering. A second theoretical model of chirality around the transition to the smectic phase is then presented which takes account of fluctuations, based on an analogy with the state of a smectic-forming material infiltrated into an aerogel. A phase resembling the TGB phase emerges from this model. The model gives two first order transitions in accordance with experiments on the TGB phase, and reflects other experimental pitch and calorimetry measurements too. The electrochemical polymerisation of an acrylate monomer in the nematic and smectic-C* phases is investigated. 30-100V is applied across a cell containing the liquid crystal-monomer mixture, with no additional initiating compound. In both phases, the texture during polymerisation is frozen in by the polymer formed. In a nematic phase in a cell with initially planar alignment, the director in the field off state can be observed to tilt toward the homeotropic over a number of hours. In the ferroelectric case, as well as the textural freezing there is a somewhat reversible agglomeration of polymer strands into micron-scale structures. Scanning electron microscopy reveals a range of structures on both electrode surfaces, including in the nematic case corrugations with a periodicity of 500-750nm. There is no evidence of a polymer network spanning the thickness of the cell - rather the liquid crystal seems to be realigned by a polymer film at the electrode surfaces.

The unique features of flexoelectric and dielectric effects are investigated, and exploited for a variety of functions, in a wide range of helicoidal liquid crystal systems, including non-chiral, cholesteric and blue phases. Electrooptic techniques are developed to measure flexoelectric parameters in non-chiral and cholesteric liquid crystals using twisted nematic and Grandjean geometries respectively. A crystal rotation method, and using a lock-in amplifier, is used to enable the measurement of a very small e/K of 0.011 C/N^-1m^-1. Enhancement in chiral-flexoelectric switching is demonstrated theoretically in liquid crystals with negative dielectric anisotropy and in systems in which the pitch is constrained to be other than the natural pitch. A methodological framework for inducing stable Uniform Lying Helix alignment is developed based on weak homeotropic alignment conditions and a method to bias the helicoidal axis orientation; a series of approaches within this framework are demonstrated, including nano-grooved interfaces, periodic boundaries conditions, in-plane fields, and mould-templated micro-channels. The latter approach is potentially commercially viable for sub-millisecond electrooptic technology. The contribution to a cholesteric material's effective dielectric permittivity of flexoelectric polarization is formulated, and an ability to switch a cholesteric between Grandjean and lying-helix configurations based on the dispersion in the flexoelectric polarization and resultant relaxation in dielectric properties is demonstrated. The flexoelectric contribution to dielectric permittivity is exploited to enable switching in bistable reflective displays and alignment of the Uniform Lying Helix. The existence of a flexoelectric contribution to Kerr switching in blue phases is demonstrated, and a semi-empirical model for the effect is developed. The effect is the first known example of a non-polar flexoelectrooptic effect. Independent flexoelectric and dielectric contributions to Kerr switching in blue phases are measured experimentally by measuring the induced birefringence as a function of driving frequency in flexoelectric- and dielectric-dominated wide-temperature-range blue phase materials.

Blue phase liquid crystals (BPLCs) have a delicate lattice structure existing between chiral nematic and isotropic phases, with a stable temperature range of about 2 K. But due to short coherent length, these self-assembled nano-structured BPLCs have a fast response time. In the past three decades, the application of BPLC has been rather limited because of its narrow temperature range. In 2002, Kikuchi et al. developed a polymer stabilization method to extend the blue-phase temperature range to more than 60 K. This opens a new gateway for display and photonic applications. In this dissertation, I investigate the material properties of polymer-stabilized BPLCs. According the Gerber’s model, the Kerr constant of a BPLC is linearly proportional to the dielectric anisotropy of the LC host. Therefore, in the frequency domain, the relaxation of the Kerr constant follows the same trend as the dielectric relaxation of the host LC. I have carried out experiments to validate the theoretical predictions, and proposed a model called extended Cole-Cole model to describe the relaxation of the Kerr constant. On the other hand, because of the linear relationship, the Kerr constant should have the same sign as the dielectric anisotropy of the LC host; that is, a positive or negative Kerr constant results from positive (∆ε > 0) or negative host LCs (∆ε < 0), respectively. BPLCs with a positive Kerr constant have been studied extensively, but there has been no study on negative ∆ε polymer-stabilized BPLCs. Therefore, I have prepared a BPLC mixture using a negative ∆ε LC host and investigated its electro-optic properties. I have demonstrated that indeed the induced birefringence and Kerr constant are of negative sign. Due to the fast response time of BPLCs, color sequential display is made possible without color breakup. By removing the spatial color filters, the optical efficiency and resolution density are both tripled. With other advantages such as alignment free and wide viewing angle, polymer-stabilized BPLC is emerging as a promising candidate for next-generation displays. However, the optical efficiency of the BPLC cell is relatively low and the operating voltage is quite high using conventional in-plane-switching electrodes. I have proposed several device structures for improving the optical efficiency of transmissive BPLC cells. Significant improvement in transmittance is achieved by using enhanced protrusion electrodes, and a 100% transmittance is achievable using complementary enhanced protrusion electrode structure. For a conventional transmissive blue phase LCD, although it has superb performances indoor, when exposed to strong sunlight the displayed images could be washed out, leading to a degraded contrast ratio and readability. To overcome the sunlight readability problem, a common approach is to adaptively boost the backlight intensity, but the tradeoff is in the increased power consumption. Here, I have proposed a transflective blue phase LCD where the backlight is turned on in dark surroundings while ambient light is used to illuminate the displayed images in bright surroundings. Therefore, a good contrast ratio is preserved even for a strong ambient. I have proposed two transflective blue phase LCD structures, both of which have single cell gap, single gamma driving, reasonably wide view angle, low power consumption, and high optical efficiency. Among all the 3D technologies, integral imaging is an attractive approach due to its high efficiency and real image depth. However, the optimum observation distance should be adjusted as the displayed image depth changes. This requires a fast focal length change of an adaptive lens array. BPLC adaptive lenses are a good candidate because of their intrinsic fast response time. I have proposed several BPLC lens structures which are polarization independent and exhibit a parabolic phase profile in addition to fast response time. To meet the low power consumption requirement set by Energy Star, high optical efficiency is among the top lists of next-generation LCDs. In this dissertation, I have demonstrated some new device structures for improving the optical efficiency of a polymerstabilized BPLC transmissive display and proposed sunlight readable transflective blue-phase LCDs by utilizing ambient light to reduce the power consumption. Moreover, we have proposed several blue-phase LC adaptive lenses for high efficiency 3D displays.

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Low power consumption is a critical requirement for all liquid crystal display (LCD) devices. A field sequential color (FSC) LCD was proposed by using red (R), green (G) and blue (B) LEDs and removing the lossy component of color filters which only transmits ~30% of the incoming white light. Without color filters, FSC LCDs exhibit a ~3X higher optical efficiency and 3X higher resolution density as compared to the conventional color filters-based LCDs. However, color breakup (CBU) is a most disturbing defect that degrades the image quality in FSC displays. CBU can be observed in stationary or moving images. It manifests in FSC LCDs when there is a relative speed between the images and observers’ eyes, and the observer will see the color splitting patterns or rainbow effect at the boundary between two different colors. In Chapter 2, we introduce a five-primary display by adding additional yellow(Y) and cyan(C) colors. From the analysis and simulations, five primaries can provide wide color gamut and meanwhile the white brightness is increased, as compared to the three-primary. Based on the five-primary theorem, we propose a method to reduce CBU of FSC LCDs by using RGBYC LEDs instead of RGB LEDs in the second section. Without increasing the sub-frame rate as three-primary LCDs, we can reduce the CBU by utilizing proper color sequence and weighting ratios. In addition, the color gamut achieves 140% NTSC and the white brightness increases by more than 13%, as compared to the three-primary FSC LCDs. Another strategy to suppress CBU is using higher field frequency, such as 540 Hz or even up to 1000 Hz. However, this approach needs liquid crystals with a very fast response time (