The electric field induced tilt angles and the corresponding optical transmission properties are presented for two homologs and a mixture which exhibit a strong electroclinic effect at ambient temperatures. Tilt angles as large as 15 degree(s) are reported. The relationship between the molecular tilt angle and the transmission properties are emphasized.

A simple theoretical model is proposed for describing thermodynamic properties of chiral- racemic mixtures. It is shown that in the case of chiral-racemic mixtures, spontaneous polarization tends to be linear and Smectic C--Smectic A transition temperature--quadratic function of the enantiometric excess, which is confirmed by our experimental data.

Anchoring phenomena and their effect on focal conic domain (FCD) instabilities in the smectic A phase were studied for two different geometries: (a) field-driven nucleation of FCDs in a homeotropic cell and (b) anchoring-driven transition in a planar cell from field-induced homeotropic state.

Orientationally ordered polymer networks are prepared in spherical and cylindrical geometries by isothermal photopolymerization of diacrylate molecules dissolved in a nematic liquid crystal. Optical polarizing microscopy textures reveal that the network memorizes the nematic director field. Diacrylate concentrations of 2% by weight suffice to create a stable network embedded in the anisotropic liquid crystal environment for temperatures as high as 150 degree(s)C. Polymer networks that are formed under various surface conditions, applied electric fields, and geometrical constraints are characterized with optical polarizing microscopy.

We present in this paper the results of our investigations concerning the effect of different types of self-assembled (chemisorbed) monolayers on the alignment of liquid crystals. While the hydrophobic monolayers tend to align liquid crystals homeotropically (molecules perpendicular to the surface), the hydrophilic monolayers, in general, lead to a planar orientation. The quality of alignment is found to depend on the degree of hydrophilicity as determined from contact angle measurements.

The collective and molecular dynamics of ferroelectric liquid crystalline side group polysiloxanes has been investigated for use of broadband dielectric spectroscopy (10^-2 Hz - 10⁹ Hz). In the lower frequency range (< 10⁶ Hz) two collective relaxations, Goldstone- and soft-mode, could be observed. They are assigned to the fluctuations of the phase and the amplitude of the helical superstructure, respectively. In the high frequency regime (10⁶ Hz - 10⁹ Hz) one dielectric relaxation, the (beta) - relaxation, is found. It is assigned to the hindered rotation (libration) of the mesogene around its long molecular axis. It shows an Arrhenius-like temperature dependence with no deviations at the phase transition S_A/S^*_C. A dilution of the mesogenes causes a decrease of the collectivity but remains the local dynamics uninfluenced.

Small angle light scattering (SALS) and optical microscopy have been used to study micron- sized liquid crystalline droplets of 4'-n-octyl-4-cyanobiphenyl (8CB) suspended in a poly(vinyl alcohol) aqueous solution. Elliptical SALS patterns in the presence of an orienting slow flow indicate that the droplets are nonspherical in shape in the smectic and nematic regimes, but become spherical at temperatures above the nematic/isotropic (N/I) transition temperature. Upon cessation of flow, the elliptical patterns relax towards isotropy on time scales comparable to the rotation diffusion coefficient of the droplets. Using direct optical microscopy, droplets of 8CB are observed to be biconcave disc-shaped, similar to mammalian red blood cells. Reversible transitions in the drops from biconcave discs to spherical shapes across the N/I transition are seen, indicating that the nonspherical shape is due to liquid crystalline ordering. It appears that the biconcave shape provides a minimum in the free energy of curvature, balancing strong liquid crystal interactions at the interface and surface tension.

Ferroelectric smectic C* liquid crystals (FLCs) have been shown to exhibit high speed electrooptic response when incorporated into the surface stabilized ferroelectric liquid crystal light valve. An important component of the FLC material used in devices is the smectic C host, which imparts many of the important characteristics to the final mixture, allowing customization to a specific type of device. A new class of FLC materials based on a cyclohexenyl core is reported and their properties evaluated in both the pure material and mixtures.

A (polymer/liquid crystal:LC) composite film, in which LC molecules are embedded in a 3D polymer matrix, shows reversible light scattering-light transmission switching upon off- and on-a.c. electric fields, respectively. The electro-optical behavior of the composite film was strongly dependent on the LC channel (domain) size in the composite film. The transmittance increased, and also, the rise and decay response times ((tau) _R and (tau) _D), decreased and increased, respectively, with an increase in the size of LC channel (domain). The electro- optical response of LC molecules is strongly influenced by the miscibility and anchoring strength of LC molecules to the polymeric wall. The miscibility between both phases was evaluated from a distribution of relaxation time for an interfacial polarization. The anchoring effect was also investigated by measuring nonlinearity of the dielectric constant for the composite system.

A scattering liquid crystal (LC) film comprises two ITO coated plastic (or glass) substrates in between which is a polymeric material containing micro droplets of nematic LC. The scattering efficiency of the film is voltage controllable. The packaging of the LC film for an optical attenuator is studied.

For the first time, glass forming low molar mass liquid crystals were synthesized exhibiting ferroelectric properties. This goal was achieved using derivatives of 2,5-dihydroxybenzoic acid with lateral aromatic branches. Several of the compounds prepared show a glass transition near room temperature occurring either in the SmA or in the SmC* phase. In the SmC* phase high values of the spontaneous polarization up to P_S approximately equals 200 nC/cm² are observed. With decreasing temperature the switching time increases by five orders of magnitude from 1 ms to 10 s. Correspondingly, Goldstone mode dielectric relaxation frequencies as low as 10^-1 Hz can be observed. In the SmA phase some of the compounds exhibit a very strong electroclinic response, i.e. tilt angles up to 10 degree(s) can be induced near the SmA/SmC* phase transition. The temperature dependence of the soft mode dielectric strength and the relaxation frequencies show strong deviations from simple critical behavior. It is demonstrated that the electrically controlled switching angle can be frozen in. The combination of this strong effect with the distinct second order optical susceptibility exhibited by the materials can be of interest for NLO-applications.

Ferroelectric liquid crystals (FLCs) find many applications in display devices, waveguide switching and optical computing. These applications exploit the electrically alignable polarization of FLCs in the Smectic C* (SmC*) phase. In the absence of an electrical field, the SmC* phase exhibits helical modulation of the polarization vector resulting in no net bulk polarization. Pitch length and polarization properties of the phase are associated with the tilted structure and chirality of FLCs. Fundamentally, these physical properties constitute secondary order parameters of the SmA-SmC* (AC*) phase transitions. In this paper, we report a unique and startling ACC* multicritical point in mixtures of chiral DOBAMBC (p-(n- decyloxybenzylidene)-p-amino-(2-methyl-butyl) cinnamate and archiral 10O.8 (4- decyloxybenzylidene-4' octylaniline) where the SmA, C, and C* (ACC* point) phases meet. Studies of the phase diagram, tilt angle ((theta) ), polarization (P) and helix pitch (p) reveal an ACC* Lifshitz point that can be described in terms of the extended Landau theory. Specifically, the T_AC* and maximum polarization (P_m) exhibit quadratic composition dependence while the helical pitch length (p equals 2(pi) /q) varies linearly. Both q and P_m vanish discontinuously at the C-C* phase boundary revealing its first order nature. Significantly, the composition dependence (x) of P_m and (theta) can be explained using percolation and thermodynamic scaling theories, respectively.

All kinds of LCDs are generally consisted of planar liquid crystal media, which are sandwiched between glass or plastic sheets. In this paper, the LC molecular conformations and their surface alignments in LCDs are systematically introduced, and the methods of LC surface alignment and their mechanisms are discussed. Furthermore the relationship between the EO performance of LCDs, such as TN, STN, Ch-N phase change, FLC, and PD-LCDs and the surface LC alignment is discussed.

Dimension Technologies Inc. has devised and experimentally validated a technique for producing field-sequential-color illumination for liquid crystal displays (LCDs) that does not exhibit image breakup and can provide flicker free images at slower refresh speeds than other field-sequential-color techniques. The technique involves a combination of colored illumination patterns that are sequentially imaged within the pixels of an LCD. An optical bench version of this type of illumination system was used to evaluate the ability to produce white light, evaluate flicker performance, evaluate image breakup visibility, and perform reading tests. This work can lead to a superior means of producing color displays using monochrome LCDs. Application of the research by LCD manufacturers may allow that industry to produce simplified, less costly LCDs for color displays.

Devices and applications of a new bistable liquid crystal are presented. This material consists of a small fraction of inorganic particles of a nanometer size dispersed in a nematic liquid crystal with positive dielectric anisotropy. Using an AC-electric field of transparent homeotropic state is obtained. It can be addressed by local optical writing using a low power diode laser, which transforms the transparent state into a strongly scattering multidomain one. The written information is stable in space and time. Local erasing is achieved by the application of a moderate voltage and a simultaneous laser pulse directed at the pixel to be erased. Based on this material a projection display system was developed. New high contrast and high viewing angle reflection and transmission displays are presented. These types of reflection displays may also be used as high resolution optically addressed, spatial light modulators for optical information processing.

Polymer-dispersed liquid crystals can be used to construct large-area architectural light shutters. Common problems in this application include off-axis haze and image bleedthrough. We describe a scheme which allows for wide viewing angles with low haze in powered films while maintaining adequate scattering at zero-fields. The scattering properties of films at low and high field states are related to the anomalous diffraction approximation for light scattering.

In general, polymer dispersed liquid crystal (PDLC) devices are based on the principle of field controlled light scattering. The effect utilized so far is quadratic and the characteristic response time is in the millisecond range. However, for many applications, a linear electrooptic response is more attractive. A few effects giving such a response are candidates of practical importance. Here, we presented three different polymer dispersed systems, incorporating short pitch smectic C*, smectic A* or N* as electrooptically active materials. By means of a special alignment technique, polymer dispersed chiral liquid crystal films with high transparency and with their optic axis lying in the film plane are prepared. When an electric field is applied across the films, a linear modulation of the transmitted light is observed, due to the field-induced-in-plane deviation of their optical axes. In all three cases, the induced tilt of the optic axis has been found to be a linear function of the applied field and the response time to be in the microsecond range. This means a fast liquid crystal electro-optic effect with grey scale. The induced tilt of the optic axis can be substantial. In the case of short pitch ferroelectric PDLC it is about 13 degrees on applying an electric field less than 10 V/micrometers and higher values are achievable with this kind of material.

Real-time (video frame rate) optical correlation and wavelet transformation using high- resolution LCTV-SLMs and Fresnel zone plates have been studied. In the systems, the LCTV- SLMs are used as real-time optical filtering devices in Fourier planes and the Fresnel zone plates are used as Fourier transformation devices. In the experiment, good optical performance has been achieved. From the results, it is confirmed that the Fresnel zone plates are suitable devices for parallel optics and using them, they can be extended parallel optical systems easily.

Unique features of optically induced orientational effects in liquid crystals are shown to underlie a number of important applications such as laser beam express analysis, power stabilizing and unidirectional limiting, duplex nonlinearity and image storage and processing.

We present the results of our structural measurements on smectic liquid crystal films deposited on photolithographed gratings on both glass and silicon substrates. These gratings have periods in the range of 664 nm - 200 micrometers , and the depths of up to 2 micrometers . We found that both silicon and glass gratings are able to align the liquid crystal in the period range 664 nm - 24 micrometers , as determined using both x-ray diffraction and optical microscopy. This result sets upper and lower boundaries for grating preparation. The results of our measurements were fit to a multilayer orientational model in order to determine the thickness of the observed aligned layer. We discuss the possible impact of our results on large area display packaging and preparation.

We describe recent progress on the polymer-dispersed cholesteric liquid crystal display. The display utilizes droplets of chiral liquid crystal with negative dielectric anisotropy in a polymer film. In zero electric field, the droplets take on the Frank-Pryce spherulitic texture which weakly scatters light. When a field is applied, the Frank-Pryce texture reverts continuously to a planar texture beginning from the center of the drop, resulting in a field-controllable reflectivity over a wavelength band dictated by the cholesteric pitch and the drop size. Results showing response times and reflection spectra for thermally-cured and UV-cured displays will be presented.