We propose an optical configuration of a twisted-nematic liquid crystal (TNLC) device driven by an in-plane electric field for a single-cellgap transflective display. The dark state of the reflective part is realized by a nematic liquid crystal layer with the twisted angle of 63.6° and the retardation of 194 nm, while a quarter-wave plate is inserted for the dark state of the transmissive part. Wavelength dispersion of the TNLC layer is suppressed by introducing a half-wave plate, whose optimum angle is found by using the Muller matrix method. Different directions of electric fields rotate liquid crystals to 15° for the bright state of the reflective part, but to -30° for that of the transmissive part. With the proposed configuration, we can realize a single-gamma transflective display in single cellgap structure without any in-cell retardation layers. By fabricating a 2.0" qCIF+ (176×RGB×220) prototype panel, we demonstrated both high reflection/transmission and single gamma of the proposed configuration.

A method for liquid crystal surface alignment by using a one-step, ion beam sputtering on glass substrates is demonstrated. Pre-coating by polyimide is not necessary. We use a diode-type sputter to treat the glass substrates with Ar ion-beam. The homeotropic alignments for nematic liquid crystals are achieved. The alignments are characterized by using the polarizing optical microscope and the conoscope. To find out the alignment mechanism, the studies by using super conducting quantum interference device and scanning probe microscopy are carried out. The surveyed surface morphology reveals that the films are amorphous and composed of nanoparticles with dimensions around 30 nm. The magnetization anisotropy of the sputtered magnetic films is analyzed. The polar anchoring strengths of the coated films with different thicknesses are measured and compared with their saturation magnetization. We deduce that the homeotropic alignment is achieved due to the orientation of the diamagnetic nematogenic molecules in the magnetic field caused by the γ-Fe₂O₃ ferrimagnetic thin films. A simple model of alternatively distributed magnetic moments with opposite direction is proposed. The profile of magnetic field strength near the surface is then calculated to compare with the measured alignment strength.

We briefly review systematic and comprehensive studies on several chlorine-substituted bent-core liquid crystal materials in their nematic phases. The results, in comparison to rod-shaped molecules, are both extraordinary and technologically significant. Specifically: a) Electrohydrodynamic instabilities provide unique patterns including well defined, periodic stripes and optically isotropic structures. b) Rheological measurements using different probe techniques (dynamic light scattering, pulsed magnetic field, electrorotation) reveal that the ratio of the flow and rotational viscosities are over two orders of magnitudes larger in bentcore than in calamitic materials which proves that the molecule shape and not its size is responsible for this behaviour. c) Giant flexoelectric response, as measured by dynamic light scattering and by directly probing the induced current when the material is subject to oscillatory bend deformation, turns out to be more than three orders of magnitude larger than in calamitics and 50 times larger than molecular shape considerations alone would predict. The magnitude of this effect renders these materials as promising candidates for efficient conversion between mechanical and electrical energy. d) The converse of this effect when the bent-core material sandwiched between plastic substrates 4 times thicker than the liquid crystal material provided displacements in the range of 100nm that is sensitive to the polarity of the applied field thus suggesting applications as beam steering and precision motion controls.

To capitalize on the unique size and shape-dependent optical and electronic properties of nanoscale particles for liquid crystal (LC) applications, detailed structure and size-property relationship studies are critical. To enhance our understanding of the thermal, optical and electro-optic effects of nanoparticles in nematic LCs we produced numerous different nematic LC mixtures containing small quantities of dispersed metal nanoparticles (i.e. gold and silver nanoclusters) or semiconductor quantum dots (i.e. CdTe nanocrystals) and studied their optical (texture, alignment, defect formation, luminescence) and electro-optic properties. Depending on several experimental parameters such as nanoparticle functionalization and concentration, as well as thermal history in combination with an applied electric field, these nanoparticle/LC mixtures with the nanoparticles differing in surface functionality, size, and core material gave rise to unique alignment effects and electro-optic responses in the two investigated nematic LC (N-LC) hosts.

Perylene monoimides and diimides have applications as luminescent materials and in organic photovoltaic devices as chromophores and conducting materials. Materials in which these compounds are oriented in a preferred direction will possess useful anisotropic properties that are not attainable from materials in which the compounds are randomly oriented. Anisotropic materials of these compounds can be prepared by taking advantage of the unique properties of chromonic liquid crystals. In this paper we describe the principles for designing perylene monoimides and diimides with desired optical properties and chromonic liquid-crystalline properties. In addition, we demonstrate the fabrication of anisotropic optical materials via organization of these compounds into a lyotropic chromonic liquidcrystalline phase.

A flexible and reflective polarizer-free display using dye-doped liquid crystal (LC) gels is demonstrated. The electro-optical performances of both scattering and absorption based dye-doped LC gels depend on curing temperatures. The dye-doped LC gel shows good reflectance ~55%, good contrast ratio~450:1 and fast response~6.5ms at curing temperature 10 °C when UV curing intensity is 2.6 mW/cm². The EO performance depends on the curing temperature. The hysteresis is independent of sampling time duration. The bending curvature is 21 mm. The response of dye-doped LC gels is faster under bending due to the bending-induced sheared force of polymer networks. The dye-doped LC gels open a new window for trimable electronic papers, decorative displays and switchable curtains.

Photopolymerization of liquid crystal monomers initiated by means of a dichroic photoinitiator provides an additional degree of freedom in controlling the morphology and structure of the liquid crystal networks formed. The absorption of the dichroic photoinitiator, and thereby its initiation rate, depends on its position towards the transversal light beam used for polymerization as well as its position towards the polarization of the light beam. The photoinitiator adapts the director profile of the liquid crystal monomer. As a result planar oriented areas aligned orthogonal to the propagation direction of the light beam polymerize faster than the ones parallel to it. Similarly, planar aligned areas with their orientation parallel to the electrical field vector of the light polymerize faster than the planar aligned areas oriented perpendicular to that. Based on this principle complex lithographic structures are built, not only forming structures in the plane of the polymerizing film but also in the third dimension along its cross-section. Additionally, applying the dichroic photoinitiator together with the principle of polymerization induced diffusion in monomer blends provides a wealth of new structures, especially when combined further with complicated, but well-controlled, morphologies such as those of twisted, splayed and cholesteric liquid crystal monomers.

We model the dynamics of shape evolution of liquid crystal elastomers (LCE) in three dimensions using finite element elastodynamics. The model predicts the macroscopic mechanical response induced by changes in nematic order, e.g. by heating or cooling through the isotropic/nematic transition or, in azo-doped materials, by exposure to light. We model the performance of LCE actuator devices including multicomponent actuators, peristaltic pumps and self-propelled robots. The goal of this work is to build a bridge between basic soft matter theory and practical materials engineering/device design. Supported by NSF-DMR-0605889.

To explore novel photoresponsive liquid crystalline polymer actuator, a new difunctional photosensitive nematic liquid crystalline monomer was synthesized synthesized in high yield (>60% overall), and polymerized via acyclic diene metathesis polymerization (ADMET) method. Nematic monomer, 4-butoxy-2'-(4-hex-5-enyloxy)-4'-(4-hex-5- enyloxybenzyloxy)-azobenzene, exhibited crystalline to nematic and nematic to isotropic transitions at 85.6 and 98.3 °C, respectively. ADMET polymerization of the monomer using Grubbs catalyst (Gen II) was performed to obtain a high molecular weight polymer. Brown colored free-standing polymer film and fiber were prepared from casting chloroform solution or from drawing polymer melt, respectively. The polymer film showed nematic liquid crystalline property with photosensitive phase transition behavior as observed by polarized microscope and differential scanning calorimetry. The photomechanical deformation of the film and fiber induced by polarized UV irradiation was investigated.

Colloidal structures assembled in confined nematic liquid crystals are examined. Theoretical predictions based on Landau-type approaches are complemented with the latest studies of laser assisted colloidal assembling. Effective colloidal interactions are particularly sensitive to the confinement and external fields. Their complexity leads to numerous stable or metastable colloidal superstructures not present in isotropic solvents. Particularly important are colloidal structures coupled by entangled disclinations. Such a string-like coupling is very robust and opens new routes to assemble new photonic materials.

Anisotropic phase-separation of liquid crystal and polymer composite is highly applicable for obtaining the durable electro-optic devices. In this presentation, the theoretical model for phase separation phenomena based on the onedimensional kinetic approach is introduced. For the applications of phase-separated LCs, we propose the fabrication of mechanically stable flexible display and electrically controllable microlens array using two- or three-dimensional anisotropic phase separation. Since LC molecules are isolated by polymer structure due to the anisotropic phase separations, resultant devices show very good mechanical stability against external pressure and stable electro-optic characteristics.

We demonstrated transmissive- and reflective-type Fresnel lenses based on dye-doped liquid crystal using photoalignment technique. The former is a polarization-independent and electrically tunable. The maximum diffraction efficiency reaches 37%, which approaches the theoretical limit ~ 41 %. Such a lens functions as a half-wave plate, and this feature could be well preserved under the applied voltage. The reflective-type Fresnel lens is based on dye-doped cholesteric liquid crystals (DDCLC). The formed lens persists without any external disturbance, and its focusing efficiency, analyzed using circularly polarized light, is ~ 23.7 %, which almost equals the measured diffraction efficiency of the used Fresnel-zone-plate mask (~ 25.6 %). The lens is thermally erasable, and rewritable. Notably, both of the transmissive- and reflective-type Fresnel lenses are switchable between focusing and defocusing states, upon application of a voltage. In addition, these devices are simple to fabricate, and have fast switching responses between focusing and defocusing state.

μThe combination of semiconductors and liquid crystals is extremely useful in order to fabricate integrated optical devices with tunable properties. The difference between the dielectric constants of the semiconductor and the liquid crystal ('dielectric contrast') is sufficiently high to obtain photonic band gap structures or resonant microcavities with high quality factor. At the same time, the characteristic frequencies can be controlled by temperature changes or external fields due to the thermo-, electro- or magneto-optic sensitivity of the liquid crystal. Here, previous investigations on microcavities embedded in silicon-based photonic crystals are reviewed and new results on integrated GaAs microdisks containing a light emitting layer of InAs quantum dots are presented. The latter show resonant modes with a typical width below 0.4 nm in the near infrared spectral range around 1.24 μm, which indicates a quality factor of 3500 and larger. By embedding a microdisk in a well-aligned liquid crystal and subsequent heating to the isotropic phase, a spectral shift of about 7 nm was observed. The results indicate a possible way of developing tunable light sources.

The authors report the effect of dynamics of phase separation on the formation of well ordered polymer structure in polymer stabilized liquid crystals. We obtained spatially-ordered polymer walls formed throughout the sample (in the film direction) and between the two substrates by the polymerization induced phase separation using a small amount of photomonomer dissolved in the host liquid crystal (LC). By varying parameters, such as type of LC, light intensity for polymerization, and concentration of the components, we are able to alter the phase-separation process and control the polymer wall formation. The polymer morphology largely depends on the director field-driven anisotropic diffusion during the phase separation process. We also found that the morphology of the ordered polymer structures provides a means of "imaging" important and potentially novel aspects of the pattern-forming LC states for new applications.

Photopolymerization offers a single-step and rapid formation of different kinds of structures in polymer-dispersed liquid crystals (PDLCs) for various applications. Here we investigate the fabrication of a computer-generated hologram in PDLCs to generate an electrically switchable optical vortex. First, a computer-generated hologram was numerically designed and then transferred to a transparency as a photomask. The photomask has an effective area of 1 × 1 cm² with a resolution of 25 μm and a pattern containing almost parallel lines with a fork-like bifurcation at the vortex core. Then the photomask was clipped onto a cell filled with PDLC materials, and subjected to a collimated Ar⁺ laser (514.5 nm) beam. The intensity impinged on the photomask was about 12 mW/cm². The optimal exposure time was 2 min in our experiment judged from the fading of the photoinitiator (rose bengal) color. Due to the photopolymerization induced phase separation between polymer and liquid crystal, an index modulation was formed between the polymer-rich and liquid crystal-rich regions. The structures inside the cell were examined under an optical microscope. A good optical vortex beam with high fidelity was reconstructed using a collimated He-Ne laser beam (543 nm). The diffraction efficiency was estimated to be about 13 - 17%. With a suitable voltage applied, the reconstructed optical vortex beam can be switched due to the index change between the polymer and liquid crystal. The experimental results show promising applications of PDLC materials in optical trapping.

High exciton diffusion lengths and charge carrier mobilities along the columns and the capability to align make columnar LCs promising materials for solar cells. Given the lack of columnar LCs based on acceptor-type aromatic systems needed for donor-acceptor heterojunction devices, we have developed novel carboxylic-functionalized arene chromophores. We found large columnar temperature ranges and widely tunable electronic properties. First device results are very encouraging, including very high open circuit voltages. This illustrates that the combination of both donor-type and acceptor-type columnar LCs can lead to solar cells with pronounced donor-acceptor junctions. The perspective of using the good transport properties of such columnar materials throughout the active layers offers thus a novel approach to highly structured plastic photovoltaic devices.

Indium-Tin-Oxide (ITO), which is commonly used in the flat-panel display industry as a transparent conductive oxide, was patterned cleanly by a non-photolithographic process. For the patterning of ITO on a silicon nitride substrate, the substrate was coated with photoresist which was patterned by the photoablation process using a KrF (wavelength of 248nm) excimer laser with low fluence conditions. ITO was then deposited on the patterned photoresist by sputtering, and the final ITO pattern was produced by lift-off. The resulting ITO pattern was clean even though it was patterned without a conventional photoresist development step and a conventional ITO etching step. This process technology does not require a developing process and an etching process to make a pattern on the substrate. A reduction of two process steps will result in substantial cost savings in high-volume production. The production time for the fabrication cycle and the equipment maintenance will also be decreased. Besides the application of this process to ITO patterning in TFT-LCD (Thin Film Transistor Liquid Crystal Display) fabrication, it can also be used for patterning other materials and device structures. It is attractive for a variety of applications in the fabrication of flat-panel displays, other microelectronic devices and device packaging, because it enables low cost and high throughput.

Recently, color reproduction stages are developed greatly, such as liquid-crystal displays, LCD TV, LCD projectors, DLP projectors, and etc. Wide-color-gamut displays are distinguishing feature of many display manufacturers. Many researches about multi-primary color displays are proposed, but there are still some problems which are not solved. This study proposed a novel multi-primary projection display system using two projectors. One of the two projectors is modified by changing two dichroic mirrors inside. The modified projector is combined with the other to a new six-primary color display. This study applies equal-luminance boundary theorem to construct gamut volume and evaluates the merit between gamut volume and brightness. By this method, the cut-off wavelength of dichroic mirrors can be found out. In the past, to align the images of the two projectors is pre-distorted to compensate the trapezoidal distortion. This study proposes to eliminate trapezoidal distortion by using the offset of the projector. This study directly changes dichroic mirrors to maintain the brightness and contrast, and solves lower brightness and contrast resulted from adding filters before. Additionally, this study uses a reflection mirror to twist projection path and also constructs a stage to align projection images more accurately.

Recently, RF driven electrodeless high intensity light sources have been implemented successfully in the projection display systems for HDTV and videowall applications. This paper presents advances made in the RF waveguide and electric field concentrator structures with the purpose of reducing effective arc size and increasing light collection. In addition, new optical designs are described that further improve system efficiency. The results of this work demonstrate that projection system light throughput is increased relative to previous implementations and performance is optimized for home theater and other front projector applications that maintain multi-year lifetime without re-lamping, complete spectral range, fast start times and high levels of dynamic contrast due to dimming flexibility in the light source system.

Two alternative methods for effectively reducing the speckle noise in laser based rear and front projection displays are studied and demonstrated. Firstly, widening of the laser emission spectrum to nearly 4nm by tailoring the structures of 640nm band AlGaInP/GaInP based edge emitting broad-area red laser diode arrays, realized a reduction of speckle contrast from 20% to an acceptable level of 5%. Designing the power/wavelength distribution of the multiple emitters to achieve a flat top profile for the total spectrum plays an important role in maximizing the speckle reduction effect. This approach could easily be adapted to laser diodes arrays of other materials or wavelengths. Secondly, relative oscillation movement within the screen layers can also reduce the speckle contrast to the acceptable level of 5%. The moving layer material and the oscillation period has been studied and optimized to maximize the reduction level for both rear and front projection configurations. The two speckle reduction techniques were evaluated on a front projector utilizing a red laser assisted UHP lamp hybrid light source, and showed significant enhancement in view ability by the suppression of speckle. Combining the two techniques lead to further reduction in speckle and scintillation noise to a supreme level of 2%, enabling a practical solution for wide color gamut and high efficiency laser projection displays.

Laser projection systems that use the flying spot principle and which are based on a single MEMS micro scanning mirrors are a very promising way to build ultra-compact projectors that may fit into mobile devices. First demonstrators that show the feasibility of this approach and the applicability of the micro scanning mirror developed by Fraunhofer IPMS for these systems have already been presented. However, a number of items still have to be resolved until miniaturized laser projectors are ready for the market. This contribution describes progress on several different items, each of them of major importance for laser projection systems. First of all, the overall performance of the system has been increased from VGA resolution to SVGA (800×600 pixels) with easy connection to a PC via DVI interface or by using the projector as embedded system with direct camera interface. Secondly, the degree of integration of the electronics has been enhanced by design of an application specific analog front end IC for the micro scanning mirror. It has been fabricated in a special high voltage technology and does not only allow to generate driving signals for the scanning mirror with amplitudes of up to 200V but also integrates position detection of the mirror by several methods. Thirdly, first results concerning Speckle reduction have been achieved, which is necessary for generation of images with high quality. Other aspects include laser modulation and solutions regarding projection on tilted screens which is possible because of the unlimited depth of focus.

Dependence on sub-micron pixel pitch and super-computing have prohibited practical solutions for large size holographic displays until recently. SeeReal Technologies has developed a new approach to holographic displays significantly reducing these requirements. This concept is applicable to large "direct view" holographic displays as well as to projection designs. Principles, advantages and selected solutions for holographic projection systems will be explained. Based on results from practical prototypes, advantageous new features, as large size full-color real-time holographic 3D scenes generated at high frame rates on micro displays with state of the art resolution will be presented.

Projection systems have the unique advantage that they can produce large images from compact devices. The specialized UHP and Ujoy lamps enabled a tremendous progress towards compact and highly efficient systems. Beyond the existing markets of rear and professional front projection new applications are possible addressing personal projection and micro-projection. These new applications can profit from laser light sources. Today laser technology is still costly and complicated especially for green wavelengths. Several competing approaches for a green laser are reviewed and the basic requirements of a laser source for projection are described.

Two novel LED recycling schemes using either recycling light pipes or recycling "collars" show promise in significantly increasing the brightness of the LED sources. Preliminary experimental data show significant brightness enhancement, especially with a relatively high chip reflectivity and/or high mirror blockage factor. Further improvement may be expected when various system parameters are optimized.