This PDF file contains the front matter associated with SPIE Proceedings Volume 8279, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Biaxial nematic liquid crystals have attracted much attention from both fundamental and application points of view, because the fast response based on the rotation of the minor director is expected. So far, different molecular designs have been proposed for the emergence of the biaxial nematic phase. Among that, we have been interested in applying "preorganization" concept on generating the biaxiality. Dimeric liquid crystal compounds have been prepared in line with this concept in which two mesogenic parts are linked by the biphenyl connecting group. The pre-organized dimmer shows an anomalous textural change, for vertically-aligned and free-standing film samples, at the smectic C (SmC)- nematic (N) phase transition, in which the Schlieren texture of the SmC changes into the other Schlieren texture of the N phase. There are two possible explanations for this textural change, i.e., the occurrence of the director change at the SmC-N phase transition or the emergence of biaxiality in the N phase. The electric-field-induced birefringence has also been measured in detail for investigating the biaxial nature of the sample.

The structure and properties of natural photonic crystals are discussed using the colored scales of the beetle Lamprocyphus augustus as an example. While the exact mechanism behind the formation of these biopolymeric photonic structures has yet to be fully explored, similarities of these structures to intracellular cubic membrane architectures are introduced. Some crucial parameters behind the formation of cubic membranes are discussed. Using these insights, intracellular cubic membrane structures are transformed into an extracellular environment.

Polymer dispersed liquid crystal (PDLC) type of liquid crystal (LC) cell structure is investigated to attain extremely large size LC layer for the millimeter waves (MMW) and/or terahertz (THz) LC device applications. It is known that the porous PMMA material (PMMA monolith) is easy to fabricate from the PMMA ethanol/water solution, and we try to use the monolith as a polymer matrix of the PDLC type LC devices. It may be possible to make arbitrary bulky structure by using suitable container for the initial solution such as Fresnel zone shape, grating shape and so on, where the thickness of the LC layer can be several millimeters.

This study elucidates electrically and all-optically controllable random lasers in dye-doped liquid crystals with adding a photoisomerizable dye. The lasing intensities and the energy thresholds of the random lasers can be electrically controlled below the Fréedericksz transition threshold or all-optically controlled sequentially with a two-step exposure of UV and green beams. The below-threshold-electric- and all-optical controllabilities of the random lasers are attributable to the effective change of the spatial fluctuation of the orientational order and thus of the dielectric tensor of LCs by changing the electric-field-aligned order of LCs below the threshold and via the isothermal nematic-isotropic phase transition of LCs, respectively; thereby changing the diffusion constant and thus the scattering strength of the fluorescence photons in their recurrent multiple scattering. This can result in the change in the lasing intensity and thus the energy threshold of the random lasers.

Lyotropic chromonic liquid crystals (LCLCs) form a columnar discotic liquid crystalline (LC) phase in aqueous solution due to the disc-like or plank-like molecular shape of chromonic dyes and their ionic peripheries. Such columnar structures in the chromonic columnar N phase can be coated on a glass substrate, and aligned in one direction by applying external forces. The resulting thin crystalline film (TCF) can absorb a polarized light parallel to the molecular axis while transmitting a polarized light parallel to the columnar axis, which constructs an E-polarizer. Although the concept of the coatable polarizer known, it has not been commercially successful due to numerous problems mainly originated from the use of aqueous solution. It is extremely difficult to coat the aqueous solution on most of substrates, especially on plastic substrates. Large volume shrinkage occurs during the crystallization process generating unfavorable defects. Also, weak adhesion becomes an important issue when a TCF is applied to a flexible substrate. In this presentation, we demonstrate a novel preparation method of coatable polarizer from a photo-curable organicbased LCLC solution. Lyotropic LC solutions were prepared by dissolving amino-functional chromonic dye in acrylic acid containing photoinitiator and crosslinking agents. The solution was shear-coated with subsequent UV irradiation to provide a thin film polarizer. The coating processibility of this organic-based solution was outstanding, particularly on a plastic substrate. The maximum polarization efficiency was measured to be > 98 %. The resulting thin film polarizer showed excellent film characteristics, such as good adhesion strength to various substrates, superior surface hardness, good solvent resistance and decent thermal stability.

We introduce a family of broadband retarders, comprised of a low number of twisted nematic liquid crystal layers, that accomplishes well-controlled polarization transformation for nearly any bandwidth desired. For example, we show that broadband linear to circular polarization conversion can be achieved with only two twist layers where the performance matches the popular three-waveplate approach by Pancharatnam. Using liquid crystal polymers on a single substrate, we show how these multi-twist retarders are embodied as a monolithic birefringent plate with excellent performance and potentially very low cost.

Binary mixtures of a phthalocyanine (Pc) mesogen and its Zn complex, which have eight decyl chains at the nonperipheral positions of Pc were studied as an organic semiconducting system. The complete miscibility was observed for the Col_h mesophase and the carrier mobility for the Col_h mesophase was measured to give small decrease of mobility in the 1:1 mixture in comparison to that of the pure compounds. These indicate that in this binary system, two compounds could mostly behave as the identical molecules and no specific interaction was expected. The different component ratio affects the carrier mobility depending on the ratio, meaning the molecular dispersion is not taken place in a monomolecular level and possibly columns formed by each compound exist to hold a certain distance for successive charge hopping. These results indicate that the mixture of mesogens could make mesogenic systems useful for new applications such as organic thin film solar cells.

The ability to control and direct self-assembly of nanostructures into specific geometries with new functionalities, while preserving their original optical and electronic properties, is an attractive research endeavor. We have fabricated liquid crystal (LC) based matrices into which chemically synthesized nanostructures of varied morphologies and compositions are uniformly dispersed. Using high resolution spatially- and time-resolved scanning photoluminescence (PL) measurements, we have demonstrated directed nanoparticle assembly and manipulation in situ. This includes (a) directional assembly and electric field modulated re-orientation of disk-shaped gallium selenide nanoparticles using a nematic LC matrix, and (b) spectral modulation of chemically synthesized core shell CdSe/ZnS quantum dots (QDs) embedded in a cholesteric liquid crystal (CLC) matrix. Our work opens up the possibility of designing new QD based optical devices where spatial control of orientation, wavelength and polarization of the embedded QDs would allow great flexibility and added functionalities.

The applications of liquid-crystal-based devices the sub-millimeter wave or THz (1 THz = 10¹² Hz) frequency range has blossomed recently. In this paper, we review the methodology for determination of the THz optical constants of nematic liquid crystals, using E7 as an example. To demonstrate potential applications, we report an electrically tuned THz Solc filter.

We investigated the phenomena of a metallic photonic crystal (MPC) immersed in liquid crystal. According to our design, the photonic crystal has specific photonic band gap (PBG) and can be utilized as a filter. The device is filled with nematic liquid crystal (NLC), MDA-00-3461. The refractive indices of NLC can be magnetically controlled by reorienting the NLC molecules. Consequently, the corresponding PBG and the filtering performance of the device are tunable. According to our experimental results, the low frequency boundary of PBG at 0.121 THz can be blue shifted by 6.17 GHz, and the high frequency boundary of PBG at 0.175 THz can be shifted to the blue by 11.04 GHz. As a tunable THz filter, the peak transmittance at 0.187 THz can be blue shifted by 3.66 GHz.

We have succeeded in observing the structure of the polymer-dispersed liquid crystal cell using SHG laser scanning microscopy combined with the Z polarization generator we have developed. The SHG phenomenon should occur in the boundary between LC molecules and the polymer surface where the inversion symmetry of LC molecules is lost. This method has the advantage of non-destructive measurement compared with the SEM imaging method.

We present here the successful preparation of liquid crystalline core-shell elastomers via a microfluidic double-emulsion process. The customized set-up allows for a temperature-controlled fabrication of the core-shell particles from a thermoresponsive mesogenic monomer. The nematic liquid crystalline shell is filled with a non-mesogenic core of silicone oil. To verify the core-shell structure with optical microscopy, we prepared particles with a colored core using a red dye. We were also able to micro-manipulate the particles and penetrate them with a small glass capillary to extract the liquid core.

"Wearable technology" or "smart textiles" are concepts that are very rapidly gaining in attention around the world, as industry as well as academia are making major advances in integrating advanced devices with various textiles around our household. The technological challenges involved in this development are however considerable, calling for new solutions, new materials and truly original thinking. An attractive approach to realize certain classes of wearable devices may be to use textile fibers functionalized by responsive materials such as liquid crystals, normally not connected to textiles. We can produce non-woven textiles with such fibers by means of electrospinning, a technique for producing very thin polymer fibers that can be uniform or with core-sheath geometries. Since the core can be made out of traditionally non-spinnable materials we can use coaxial electrospinning (one fluid spun inside another) to produce composite fibers with a core of liquid crystal inside a polymer sheath. The resulting fibers constitute an entirely new configuration for applying liquid crystals, giving the fibers functionality and responsiveness. For instance, with a cholesteric core we can produce non-woven mats with iridescent color that can be tuned (or removed) e.g. by heating or cooling. In this paper I describe our method of producing these novel functionalized fibers and their characterization, and I will discuss the directions for future research and application possibilities, e.g. in clothing-integrated sensors and indicators.

We report on the design and fabrication of 'smart surfaces' that exhibit dynamic changes in their surface topology in response to exposure to light. The principle is based on anisotropic geometric changes of a liquid crystal network upon a change of the molecular order parameter. The photomechanical property of the coating is induced by incorporating an azobenzene moiety into the liquid crystal network. The responsive surface topology consists of regions with two different types of molecular order: planar chiral-nematic areas and homeotropic. Under flood exposure with 365 nm light the surfaces deform from flat to one with a surface relief. The height of the relief structures is of the order of 1 um corresponding to strain difference of around 20%. Furthermore, we demonstrate surface reliefs can form either convex or concave structures upon exposure to UV light corresponding to the decrease or increase molecular order parameter, respectively, related to the isomeric state of the azobenzene crosslinker. The reversible deformation to the initial flat state occurs rapidly after removing the light source.

We review the current understanding of stress-free, defect-driven deformations in thin sheets of nematic solids, from simple, isolated cone-forming +1 disclination defects to more complicated textures constructed from simple building-block domains. Further, by building from these textures we may investigate the effect that grain boundaries of various types have on the material deformation, leading to faceted tubes in some cases and lines of Gaussian curvature, instead of points, in others.

In great majority of the previous works devoted to photonic liquid crystal fibers (PLCFs) a photonic band-gap propagation was investigated, since silica glass fibers' refractive index is lower than refractive indices of the most of liquid crystals. In this work we focus on the electrical tuning of the index-guiding PLCFs based on host-fibers made from multi-component glasses with enhanced value of refractive index. Impact of the electric field on the light propagation in index-guiding PLCFs has been carefully studied and effective tuning of the phase birefringence, attenuation and polarization dependent losses has been observed experimentally.

We have fabricated field sequential color (FSC)-LCDs using cells and modules of narrow-gap TN-LCDs with and without doping the nanoparticles of PCyD-ZrO₂ and AF-SiO₂. It is shown that the FSC-LCD exhibits a high optical efficiency of OE=4.5 that is defined as OE=[Luminance]/[W/m²]=(cd/W). This figure may provide us a good reference or to clear the Energy Star Program Version 5-3 that issues a guideline: LCD with 50 inch on the diagonal consumes the energy of 108W. Through this research it is claimed that our FSC=LCD may be a novel green digital signage.

We present our numerical attempts to simulate the structures of a cholesteric blue phase (BP) confined in a thin cell. Our simulations are based on a Landau-de Gennes theory describing the orientational order of the liquid crystal by a second-rank symmetric tensor. When the cell thickness is small enough, of the order of the lattice constant of the bulk BP a, various exotic defect structures that do not resemble those of bulk BPs are shown to be stable. They include a hexagonal lattice of Skyrmion excitations, and arrays of disclination lines in a double-helix form. We also show the dynamics of disclination lines in a thicker cell (~ 2.6 a) under an applied electric field. The cell before the application of an electric field accommodates disclination lines of the form similar to that of bulk BP. The electric field alters their form in a non-trivial way depending on the field strength.

Blue phase shows one the fastest switching via induced birefringence by an external electrical field observed in liquid crystals. However, the pure blue phase typically has a narrow temperature range. Applying polymer-stabilization using reactive mesogens, a blue phase with a largely increased temperature range of up to 60 K can be obtained. Prerequisite for a good stabilization is the adequate matching of RMs and the optimized polymerization conditions. To achieve a low operating voltage of the polymer stabilised Blue phase display device, the material properties of the host - namely the product of the optical birefringence Δn and the electrical anisotropy Δε - has to be optimised. New host developments yielding a largely increased Δn * Δε ~ 40 at room temperature are presented.

We have already used photoalignment and photopatterning materials to align LC in superthin photonic holes, curved and 3D surfaces and as cladding layers in microring silicon based resonators. We have proposed optical switches, tunablefocus LC lenses, photo-patterned micropolarizer array for complementary metal-oxide-semiconductor (CMOS) image sensors and other photonics liquid crystal elements based on LC photoalignment and photopatterning.

We have developed two approaches for controlling the pretilt angles of liquid crystal molecules by using conventional polyimide (PI) alignment materials either doping homogeneous PIs with Polyhedral Oligomeric Silsequioxanes (POSS) nanoparticles or treating homeotropic PIs with ultraviolet light. These techniques are very simple and are compatible with current methods familiar in the LCD industry. The characteristics of modified PI alignment films and their applications for photonic devices are demonstrated in this paper.

We here report on the alignment and electro-optic properties of nematic liquid crystals (LCs) either containing nanoscale particles as additives or featuring particles patterned on substrates. The investigated nematic LCs or LC dispersions are doped or in contact with magic-sized semiconductor CdSe nanocrystals (MSNCs) or silane- and alkylthiol monolayercapped gold nanoparticles. Three single-sized CdSe quantum dots capped with myristic acid exhibiting bright bandgap photoluminescence (PL) at λ_max ~ 463 nm were tested as additives. Two of the quantum dots only vary in the amount of defects as indicated by different bandgap and deep trap PL. The third MSNC sample is compositionally different, doped with Zn. These MSNCs with almost identical sizes were doped at different concentrations (1-5 wt%) into the nematic phase of the 2-phenylpyrimidine-based LC1. Only the Zn-doped MSNCs showed the formation of birefringent stripes surrounded by areas of homeotropic alignment between plain glass slides at all concentrations as observed for many other nanoparticle-doped nematic LCs reported earlier by our group. In polyimide-coated glass slides favoring planar orientation of the nematic director, planar alignment was observed. Similarly, siloxane-coated gold nanoparticle additives with narrow size distribution, but larger size, show homeotropic alignment between plain glass and planar alignment in rubbed polyimide-coated cells. Surprisingly then, we succeeded in creating alignment patterns using smaller, ~2 nm alkylthiol-capped gold nanoparticles using a process called stenciling that allowed us to generate patterns of homeotropic alignment in a continuum of planar alignment of the nematic LC. Finally, electro-optic investigations on some of these samples revealed that only the Zn-doped magic-sized MSNCs significantly lower the dielectric anisotropy as well as the splay elastic constant of the nematic host, despite identical size and surface functionality of the three used MSNCs, which highlights the tremendous effect of the nanocrystal core composition on the electro-optic properties of the nematic host.

In the present paper, we describe the synthesis and characterization of six new bent -shaped molecules carrying the 2-methoxy-3-cyanopyridine as a core possessing an outer phenylene unit at the lengthening arm with different alkoxy chain lengths (C-10 and C-12). Mesomorphic behaviors of the new compounds were investigated using optical polarizing microscope and DSC studies. Also, the effect of structural variables on mesogenic properties was studied. All the new cyanopyridine derivatives showed good liquid crystalline properties and exhibit smectic phase.

We show the optical characterization of a Polymer Dispersed Liquid Crystal which was made mixing Norland Optical Adhesive No. 65®, nematic liquid crystal and crystal violet dye, deposited between two glass substrates with indium tin oxide (ITO) as electrodes. In this device, we recorded low frequency (104 lines/mm) holographic gratings made with the interference of two beams from an Ar laser at 515 nm in emission line. We measured the diffraction efficiency of the gratings obtaining 2% when the grating was read with a beam from a He-Ne laser at 612 nm.

Spectral characteristics of the interference optical filter based on a free-standing mesoporous silicon film containing nematic liquid crystal E7 are studied experimentally. The porous structure represents two distributed Bragg reflectors divided by a quarter-wave microcavity having resonance near 1600 nm. Transmission spectra of the filter are measured in the temperature range from 27°C to 80°C. For the temperatures less than 62°C (clearing point of the liquid crystal), we have observed continuous red shift of the microcavity resonant wavelength in the range of 11 nm. Measured thermal dependence of the shift has sharply increasing slope near the clearing point. For temperatures exceeding 62°C the microcavity resonant wavelength exhibits slow linear decrease. We have also investigated spectra of the filter using local heating of the sample with laser. Our studies have shown, that laser beam with power of 100 mW provides total tuning of the microcavity.

We study pretilt angle control of liquid crystal from homogeneous to homeotropic using phase separation techniques of photocurable prepolymer by UV irradiation. Pretilt angle was controlled by changing the weight ratio of LC/photocurable prepolymer in homogeneous polyimide (PI) coated LC cell. Homogeneous alignment was observed in LC/photocurable prepolymer mixture of weight ratio of 99.9:0.1 after UV irradiation for 20 minutes. Tilted alignment was observed in weight ratio of 99.8:0.2. Finally homeotropic alignment was observed in weight ratio of over 99.7:0.3.