FLCs exhibit the electro-optic speed necessary for construction of full color, high resolution DRAM-based microdisplays. Special FLC materials are required to meet the performance characteristics required of these reflective microdisplays. The specifications for FLC mixtures for several applications, and an approach to formulating them, is presented herein.

Different structures of laterally fluorinated tolane and diphenyl-diacetylene liquid crystals were synthesized and their physical properties evaluated. Some of these compounds exhibit relatively low melting temperature, small heat fusion enthalpy, large negative dielectric anisotropy and high resistivity. The fluoro-tolanes possess a modest birefringence and are useful for high contrast displays employing a homeotropic alignment. On the other hand, the fluoro diphenyl-diacetylenes have a larger birefringence. Their potential applications are in the infrared spatial light modulators and millimeter wave phase shifters.

The chiral thioindigo dye (R,R)-5,5'-dinitro-6,6'-bis(2- octyloxy)thioindigo has been synthesized in optically active form and doped into a racemic S_C liquid crystal host (x_d equals 0.028) to induce a ferroelectric S_C* phase. Irradiation of an aligned sample of this induced S_C* phase at (lambda) greater than 450 nm produces a cis- enriched photostationary state of the dopant, and an increase in the spontaneous polarization of the S_C* phase by a factor of 1.8. This modulation is reversible via thermal relaxation of the dopant to the trans-form.

Development of high-performance liquid crystal (LC) phase modulators requires accurate control of the thickness and uniformity of the LC cell. Consequently, precise measurement of spatial thickness variations in these cells, which may be tens of microns thick, is a key requirement for evaluating and improving device quality. However, ambiguity problems render single wavelength interferometric methods unsuitable for this task. A practical solution is white-light interferometry (WLI) which has an essentially infinite unambiguous measurement range. For cell measurement, the path difference between the two interfering beams is set by the cell thickness, thus ruling out the commonly used coherence scanning method of WLI. Instead, we use an optical scanning method: analyzing the spectral fringes formed when white light reflects from a cell's bounding surfaces in order to map its thickness with nanometer resolution. We describe a number of experimental configurations and data processing schemes which allow us to maximize vertical and lateral measurement resolution while keeping data acquisition time and storage requirements to a minimum. We also point out that the technique can be used to characterize the switched states of phase modulators and for high-resolution surface profiling. We demonstrate the latter, showing preliminary results from a noncontact profiler based on this principle.

Due to inversion symmetry, uniform nematic liquid crystals do not show second harmonic generation (SHG) in the bulk. The inversion symmetry may be broken by spatial variation of the director field. We have studied SHG in nematic cells with spatially periodic distortions of the director field. Cells were constructed with optically patterned alignment layers on the cell walls, and filled with the liquid crystal E7. Using 35 ps pulses from a mode-locked Nd:YAG laser at 1.06 microns, we observed bulk SHG, and measured the intensity and polarization of the SH signal as a function of angle, pump polarization and temperature. We propose a simple model for the symmetry breaking polarization and the resulting SHG, and consider phase matching in inhomogeneous periodic birefringent media.

TN-LCDs having multidomain subpixels have been fabricated using photoalignment. These TN-LCDs exhibit a homogeneous and wide viewing angle. This paper places an emphasis on four domain TN-LCD called super multidomain (SMD). The SMD- TN-LCD exhibits the maximum performance among other multidomain TN-LCDs which is shown in terms of computer simulation and experimental measurements done by the author's group. A non-rubbing technique is required for SMD; we also show that photoalignment is useful for fabricating SMD-TN-LCD. Some performance of an SMD-TN-LCD are demonstrated.

Planar and homeotropic orientations of nematic liquid crystals have been obtained using novel alignment layers which were prepared by plasma-activated chemical vapor deposition (CVD) of a hydrocarbon vapor. Optical constants and porosity of the layers were characterized ellipsometrically. Layer surface energies were estimated from measuring the contact angles. Molecular structure of the alignment layers and orientation of the liquid crystals on their surfaces were studied using the IR spectroscopy. The layers are transparent in the visible region and their refractive index is very close to that of the liquid crystal. The determination of a dichroic ratio and of an order parameter of the IR absorption bands of the aligned liquid crystal shows the planar and homeotropic alignment of cyanobiphenyl molecules to be stable on the alignment layers.

The MACH (multiple, active, computer generated hologram) is a novel device combining aspects of computer generated holography with electrically controllable diffraction gratings. As such, it provides an interesting capability, falling somewhere between that of conventional fixed hologram and electrically addressed spatial light modulator (SLM) approaches to wavefront generation. Under the control of a single applied voltage, the device can selectively generate any one of a number of desired, uncorrelated optical wavefronts or wavefront transformations. Compared to the SLM, it is considerably more economical to fabricate, requires fewer supporting electronic subsystems, is more reliable and promises higher space bandwidth products. The device operating principles are outlined, showing that the ultimate performance of the MACH is, to a large extent, governed by the ability to determine the required substrate surface relief pattern. The various approaches to optimizing this highly constrained design problem are then described. These include developments of the direct search (pixel flipping) and projection algorithms. The latter in particular seem to provide an efficient way of calculating analogue, pixelated profiles, necessary for high performance MACH devices. Example results from various device optimizations are given. Following a discussion of rigorous device modeling and fabrication techniques, initial experimental results are presented, and potential applications discussed.

Liquid crystal waveplates are known as efficient phase or wavefront modulators for applications requiring the active control of laser beams such as beam steering, focusing or diffraction. In developing such devices researchers have used so far two types of electrode structures: (1) the discrete structure where the liquid crystal is modulated by means of a large number of independent narrow stripe-shaped low-resistive electrodes, and (2) the continuous structure where broad electrodes with areas of different resistivities modulate the liquid crystal via a linear or nonlinear voltage gradient generated in the electrode plane. The former approach has the advantage of high transmission efficiency and unproblematic fabrication of the electrodes. The huge number of electrodes requires however a high expenditure in fabricating the complex LC driver. The latter approach keeps down the complexity of the LC driver, however, a high optical throughput has not yet been reported. In this paper, we present an electrode design that aims at combining the advantages found in both approaches. The usefulness of the novel electrode design was verified for the first time in an experiment demonstrating the nearly diffraction limited performance of an adaptive LC microlens array.

A highly accurate measurement technique has been developed and applied for characterization of the complex transmittance of liquid crystal light valves (LC-LV). The measurement setup is based on a two-beam interference with partially coherent light. An arc lamp light source enables measurements over a large range of wavelengths. We propose a new Fourier transform interference pattern evaluation technique with a high signal-to-noise ratio. Calculations are sped up by FFT algorithms. Measurement results of the complex transmittance are shown for a twisted nematic and a Freederickzs liquid crystal light valve, built in our laboratory.

The pyroelectric properties of three chiral smectic liquid crystalline materials have been investigated. The magnitude of the pyroelectric coefficient for in two of these compounds is very high exceeding 200 nC/cm2K. A mixture containing one of these compounds exhibits a high pyroelectric coefficient over a temperature range that is attractive for thermal (or IR) sensing applications. The relevant figure of merit of these materials as elements for IR sensors is discussed in comparison to those that are currently used in sensing devices.

We present a binary reflective spatial light modulator (SLM) constructed using a patented ferroelectric liquid crystal (FLC) technique. The device is built atop a planarized 0.6 micrometer CMOS SRAM backplane with 15 micrometer pixel pitch and 88% fill factor. The device achieves better than 25% optical throughput when used with collimated laser light and better than 100:1 contrast when oriented for amplitude modulation. When oriented for phase modulation, the device achieves 180 degrees of phase shift between its 2 states. The device can be operated as fast as 5 kHz with complete switching of the liquid crystal. Applications in the fields of optical computing and optical information processing are suggested.

Reversible and bistable electro-optical switching characteristics have been investigated for induced smectic composite systems composed of side chain type nematic liquid crystalline polymer (nematic LCP) or its copolymer with weak polar methoxy terminal groups in the side chains and low molecular weight nematic liquid crystals (nematic LCs) with strong polar cyano end group. The liquid crystalline copolymer (LCcoP) with weak polar methoxy terminal groups in the side chains was used in order to improve the response speed of the bistable and reversible light switching for the binary composite system at room temperature. Although the LCcoP with 52.5 mol% substituted mesogenic side chains did not exhibit any mesophase characteristics at any temperature, this LCcoP induced a smectic state by mixing nematic LCs. A reversible and bistable electro-optical switching with a short response time (approximately 100 ms) was realized for the induced smectic binary composite system upon application of an appropriate electric field at room temperature.

With the aim of developing a wide viewing angle liquid crystal display (LCD), we are trying to apply in-plane switching (IPS) mode, in which liquid crystal molecules are switched by a lateral electric field, to TFT-LCD. We have studied the detailed relationship between the electro- optical properties and the various panel conditions. From these results, we specified the panel conditions, such as plus 10.4 dielectric anisotropy of liquid crystal material, 3.5 micrometer panel gap and 8 micrometer electrode spacing, to fabricate the IPS mode TFT panel. We have achieved the IPS mode TFT color panel that possessed not only wide viewing angle characteristics over 80 degrees with no reversed image but also a fast response time 50 ms, a low driving voltage compatible with ordinary twisted nematic (TN) mode TFT panel and a fine white balance, (x,y) equals 0.32, 0.34).

Wavefront-modulating (holographic) displays have the potential to become the ultimate 3D display, producing most of the visual cues necessary to experience depth. One of the main constraints in producing such displays is the high density of pixels that is required. Using gradient-index pixels (GrIPs), we show how the number of pixels, and hence the complexity of the display, may be reduced by orders of magnitude. With current liquid crystal display technology it is feasible to build such displays. The concept of the GrIPs may be applied to 2D displays, in which the amplitude rather than the phase is graded across each pixel. We show that these pixels have the potential to improve the image quality or reduce the pixel count in 2D displays.

In a conventional liquid crystal display device (LCD), glass substrates coated with an indium tin oxide (ITO) layer are typically used for the application of an electric field to the liquid crystal material. For many applications, there is a need for a LCD with a plastic substrate. Polypyrrole is a well known conducting polymer for its high conductivity and chemical stability. Compared with the currently used ITO conducting layer, polypyrrole is more compatible mechanically with plastic. Because it is an organic material, it should be able to bend and flex with the substrate. Therefore, it is a good candidate for the conducting surface needed in a plastic LCD. Here we present the preparation of polypyrrole films on a polyethylene terephthalate (PET) substrate by an in-situ solution deposition process and their patterning by conventional photolithography techniques. We discuss their important physical properties, such as surface resistance and optical transmission, and their suitability as a substitute for ITO as an electrode for a plastic reflective Ch-LCD.

There is a great deal of interest in reflective cholesteric liquid crystal displays (Ch-LCDs) because they are lightweight, low power flat-panel displays. Furthermore, Ch- LCDs can be made bistable which allows for the manufacture of large area, high-resolution displays without the need for expensive, difficult to manufacture active matrix addressing schemes. Also, the bistability enables flicker-free operation. Currently, these displays are made using glass substrates. However, some applications require rugged (i.e., nonbreakable), flexible displays. The use of a plastic substrate would fulfill these requirements. The transparent metal indium tin oxide (ITO) is currently used as the conducting electrode on glass as well as plastic substrates. While ITO works well with glass, it does not adhere as well to plastic, is brittle, and has a tendency to break under constant bend conditions. In this paper, we investigate substituting the more robust conducting polymer for ITO as the display electrode and determine the feasibility of producing a reflective Ch-LCD using plastic substrates with conducting polymer electrodes.

Ferroelectric liquid crystal over VLSI silicon spatial light modulators have been successfully employed as input and filter devices in optical correlator architectures for image processing and target recognition. A considerable limitation of these systems is their difficulty in extracting the desired target from clutter, particularly where this clutter has similar characteristics to the target. We present a novel set of image processing techniques for improving the target to clutter ratio, thereby simplifying the task of achieving correct target recognition. A stereo-pair of images captured from the input scene is enhanced using morphological image processing functions implemented as convolutions with an output threshold. Stereo pairs allow extraction of regions of interest based upon range. These regions are automatically extracted from the enhanced images ready for target recognition via a conventional correlation function. The clutter reduction algorithm does not require a priori knowledge of the target and so is a robust method for target recognition. All of the functions used can be expressed in terms of correlations and convolutions with an output threshold, allowing implementation on a correlator processing architecture. Initial experimental results from a Vanderlugt 4f optical correlator utilizing SLMs 256 by 256 pixel at the input and filter planes are presented. These results are compared to those from computer simulations and the performance of the optical system is assessed.

This work is dedicated to studies of electro-optical, time and modulation characteristics of nematic-cholesteric mixtures with an induced spiral structure with aim to create on this base an effective low-frequency modulator of visible range radiation. The temperature and control pulses parameters influence on the mixtures working characteristics are studied.

This work is dedicated to physical properties and electro- optical parameters of nematic-cholesteric mixtures on the base of cianobipheniles and oxycianobipheniles with aim of their using as an optical active dopants for optical information reflection devices.

We present new experimental results on bistable nematic display, controlled from surface anchoring breaking. Using simple planar anchorings on both plates and chiralized 5CB material, we prepare thin cells with two equal energy states: one uniform planar and the other one twisted by 180 degrees. Applying short electric pulses we break transiently both surface anchorings (to write) or only one of them (to erase). After these short pulses, in absence of any field, we obtain at will the uniform state or the twisted one, with infinite lifetime and full bistability. Using polarizers an optical contrast of 50 is measured between the two states. The write/erase pulse duration is short, comparable with the surface anchoring response time approximately 10 microseconds. The optical response time, classically related to the cell thickness, is here in the ms range. The temperature dependence of the threshold is also discussed. The existence of the two relatively close writing and erasing thresholds allows in principle simple multiplexability.