We show that light-induced modification of the anchoring conditions can lead to an extraordinarily large optical response in dye-doped nematic liquid crystals. The bulk reorientation due to the collective elastic behavior of the liquid crystal is the origin of the nonlinearity, which occurs without a direct optical torque on the molecular director in the bulk, We call this effect SINE (Surface Induced Nonlinear Effect). These results can also explain the origin of the supra-nonlinear behavior recently observed in the same composites.

Holographic techniques offer a route to the generation of 3D images having all the depth cues used by the human vision system. A new electro-optic modulator system has been developed by the authors to replay dynamic holographic images. This Active Tiling (AT) system offers a route to replay giga-pixel computer generated holographic (CGH) images with video refresh rates. A key component of the AT system is an Optically Addressed Spatial Light Modulator (OASLM), onto which segments of the large pixel count CGH are loaded or written sequentially before the whole CGH frame is read out simultaneously. The OASLM device structure used consists of an amorphous silicon photosensor layer combined with surface stabilised ferroelectric liquid crystal (SSFLC) light modulation layer. A number of experiments have been conducted to determine the performance and suitability of this device for replaying a CGH. These experiments include electro-optic switching to determine the operating window and diffraction efficiency (DE) measurements to determine spatial resolution performance. A detailed description of the experimental apparatus and method used for measuring DE is presented, and results show the OASLM to be capable of diffracting light from fringe patterns with spatial periods as low as 3 micrometers (333 lp/mm). Examples of CGH replay of 3D images from the OASLM when operating within the AT system are also presented.

Two novel concepts of liquid crystal (LC) diffractive structures are introduced and analyzed. Both structures are aimed at overcoming the fringing field effect in thin LC cells while allowing sufficiently large phase dynamic range to be attained. The first structure is a combination of a sub-wavelength metal grating configuration, combined with a built-in reflective, blazed grating structure and a uniform thickness LC cell. The reflective blazed grating provides a periodic, linear phase modulation, while the metal-strip sub-wavelength grating acts as a polarization-sensitive transparent multi-electrode element. The thin liquid crystal layer provides the spatially-varying dynamic phase profile. It is shown that this structure allows a triple-beam deflection operation. A diffraction analysis based on the LC director simulation shows a diffraction efficiency of over 66% in all three diffraction angles. A detailed high-spatial resolution analysis of the fringing field effect on the LC alignment for this structure is described. The second configuration is based on a built-in blazed diffractive grating, composed of two optical substrates with different refractive indices and a uniform-thickness LC layer, enclosed in a Fabry-Perot cavity. It is shown that this structure which overcomes the difficulties of LC alignment and fringing field effects in hybrid, blazed LC-glass structures, allows a dynamic switching of a laser beam with a diffraction efficiency exceeding 75%.

The road from a new technology's proof-of-principle prototype to commercially successful products always seems to be more challenging, more expensive, and longer than its inventors had imagined. Displaytech built its first experimental FLC-VLSI SLMs in 1989, began ramping up its efforts to commercialize FLC-VLSI displays around 1995, and now is building more than 100,000 displays per month with its manufacturing partner Miyota. Here we review the motivation for using FLC-VLSI technology and trace the developments that were necessary for its commercialization. We discuss problems that had to be overcome in FLC materials, device design, manufacturing, applications, product definition, and systems support in order to develop the technology and to lower barriers to its adoption by customers. The principal focus here is on technical challenges encountered in manufacturing and in FLC materials development that had to be met to go from hand-built prototypes to mass production. We also review future potential markets other than displays and describe some of our work on experimental FLC-VLSI devices that addresses those opportunities. Examples include holographic optical data storage, 3D projection, optical image processing, smart-pixel SLMs, and high-speed computer interfaces needed to support high frame rate SLMs.

Resonant cavity Fabry-Perot structures with embedded multiple quantum well layers are used to create spatial light modulators for a number of signal processing and optical beam steering applications. A review of the SLM development including modulator design considerations, our general approach to modulator-driver integration, and array formats previously demonstrated, will be presented (linear arrays up to 2048X1 and two-dimensional arrays up to 256x256). Optical transitions in MQW structures are inherently fast ($GTR$GTRns switching times) so that SLMs based on these structures can exhibit high frame rates. The optical modulator is based on a p-i-n device design operated in a reverse bias mode. The speed of the array depends primarily on the speed of the drive electronics (based on the available CMOS or other electronic drivers), the impedance of the individual modulator device, and the scheme used to bring data into the hybrid modulator/driver module. The current drivers are based on mixed signal designs that use 0.5 square m high-voltage CMOS technology and a 50-MHz data rate. Several examples of the use of the modulators will be given, including the application of the SLMs to hyperspectral data processing and optical beam steering.

For the past five years, Digital Light Processing (DLP) technology from Texas Instruments has made significant inroads in the projection display market. With products encompassing the world's smallest data & video projectors, HDTVs, and digital cinema, DLP is an extremely flexible technology. At the heart of these display solutions is Texas Instruments Digital Micromirror Device (DMD), a semiconductor-based light switch array of thousands of individually addressable, tiltable, mirror-pixels. With success of the DMD as a spatial light modulator in the visible regime, the use of DLP technology under the constraints of coherent, infrared light for optical networking applications is being explored. As a coherent light modulator, the DMD device can be used in Dense Wavelength Division Multiplexed (DWDM) optical networks to dynamically manipulate and shape optical signals. This paper will present the fundamentals of using DLP with coherent wavefronts, discuss inherent advantages of the technology, and present several applications for DLP in dynamic optical networks.

Multiple quantum well spatial light modulators (MQW SLMs) are promising devices for future high-speed applications. We present results obtained with a single-pixel amplitude modulator. We discuss the status of our work on a 128x128-pixel ternary SLM. This SLM will run at 10 kHz and have one low-reflectance level and two high reflectance levels with a phase difference of pi. We also present a study of the relation between the coding domain and the structural design of modulators.

For wavefront sensing, wavefront shaping, and optical filtering, spatial light modulators can be very useful. With the availability of high resolution liquid crystals (LC) spatial phase modulators and micromechanical systems (MEMS) containing large arrays of micromirrors, new applications in optical metrology become possible. For wavefront analysis and correction, dynamic CGHs are used. A correction hologram for the aberrated system is computed from which the lens shape can be derived. For Hartmann sensors, usually static microlenses are used. It was found advantageous to generate dynamic microlenses in order to correct for local wavefront aberrations. Optically addressed spatial light modulators can be applied very effectively for the characterisation and defect analysis of primarily periodic structures such as microchips or microlens arrays. For triangulation based methods, better results can be obtained by adapting the projected fringes to the object in terms of shape and brightness. Examples and experimental results are discussed.

Optical interconnections and integrated optoelectronic devices are expected to be promising candidates that expand interconnection bandwidth between large-scale integrated circuits (LSIs). We have constructed an optoelectronic parallel computing system that has a reconfigurable free- space parallel optical interconnection module called OCULAR- II. It has a multi-layer architecture that eliminates the data transfer bottleneck between optoelectronic processing modules by reconfigurable free-space optical interconnections. An optoelectronic processing module is composed of a two-dimensional processing element array where each pixel has its own optical output channel by a VCSEL and optical input channel. The optical interconnection is integrated into a compact module where an optically addressable phase only spatial light modulator and an imaging optical system are compactly fabricated. Each component of the OCULAR-II system has been designed to be modular and compact. Therefore, just cascading optoelectronic processing modules and optical interconnection modules makes a pipelined parallel processing system. In the optical interconnection module, a custom designed Fourier Transform lens has been used to reduce the working distance of the lens system. A computer generated hologram (CGH) is written on a liquid crystal display (LCD) that is coupled by a fiber optic plate (FOP) to the optically addressable SLM. The interconnection topology between optoelectronic chips is controlled by changing the CGH patterns, which is calculated in advance. A global interconnectivity among processor arrays is also achievable since the communication channels are constructed via optical path in free space. The data broadcasting between processors that are located spatially far away can be efficiently implemented by free-space optical links in OCULAR-II's optical interconnection module.

Multimedia databases are characterized by massive storage requirements and the need for an extremely high processor/memory bandwidth. In addition, the diversity of data types and their varying sizes and formats make multimedia database processing a formidable task. Optical and optoelectronic technology can contribute devices and system solutions with high time-space bandwidth. Spatial light modulators constitute one such class of devices. In this paper, we outline the desirable properties of spatial light modulators for multimedia database processing and review a number of devices and the systems they have been used in. Special attention is paid to holographic associative processing. We also describe a free-space optoelectronic system that employs arrays of vertical cavity surface emitting lasers integrated on CMOS to perform similarity searches on databases of biological data.

We show the feasibility of two new programmable diffractive optical elements (DOE). On one hand, we demonstrate the realization of programmable apodizers. With the term apodizer we refer to non-uniform amplitude filters used to modify the point-spread function (PSF) of an optical system. On the other hand, we show the simultaneous realization of a Fresnel lens and an amplitude filter in a single DOE: the programmable amplitude apodized Fresnel lens (PAAFL). Two different modulation regimes are required to generate these DOEs: amplitude-only regime for the programmable apodizer and phase-only regime for the PAAFL. We show that a twisted-nematic liquid crystal spatial light modulator (TN-LCSLM) inserted between two wave plates and two polarizers is able to provide both modulation regimes. Different types of amplitude filters, such as axial hyperresolving, transverse apodizing and transverse hyperresolving have been implemented both as programmable apodizers and as PAAFLs. We provide experimental results for the performance of the two new DOEs. The agreement with the numerical results is excellent, thus demonstrating the feasibility of our proposal.

During the high speed processing, the intensity of the light beam must be detected and converted into some digital signals without electronic device for system controlling. The A/D converting should be in full optics way. The interferometer may make some fringes correspond the input light, while the fringe intensity contains some important information. When a photorefractive material was put into the interference field, another reading-laser beam would be diffracted. The order of the diffraction can be controlled because the nonlinear reactivity of photorefractive materials. Then, the reading laser beam goes into an encoder to demodulate signals. Through the demodulating processing in light speed, the group-codes may be output as the input signals of other control system. The speed of the modulating should be tied from the photorefractive materials. The important step is how to change the time domain information into space domain information. If the responding speed of the photorefractive material is suitable to react on the input signal light, the conversion is successful. In that process, organic photorefractive materials or crystal photorefractive materials have different application features.

A reflection-type spatial light modulator using twisted nematic (TN) liquid crystal (the liquid crystal pixel mirror or LCPM) is employed to realize a new type of digitally tunable, narrow line-width (less than 0.1 nm, instrument-limited), multi-wavelength semiconductor laser. The laser is based on a novel folded telescopic grating-loaded external cavity with LCPM at the focal plane of the folded telescope. With a 50-pixel LCPM, the single wavelength digitally tunable range of a visible laser diode was from 650.8 to 661.24 nm in 0.21 nm steps by biasing the individual pixels. Further, the wavelength can be switched and reset with a response time of 13.6 ms. By biasing two pixels at the same time, obtain dual-wavelength output with the wavelength tunable from 0.21 to 10.4 nm. Generation of tunable triple wavelengths with equal or arbitrary wavelength separation are also demonstrated. Preliminary results on such a laser operating at 1550 nm is also shown.

There is a growing need for developing 3D quantitative imaging tools that can operate at high speed enabling real-time visualization for the field of biology, material science, and the semiconductor industry. We will present our 3D quantitative imaging system based on a confocal microscope built with a Texas Instruments Digital Micromirror Device (DMD). By using the DMD as a spatial light modulator, confocal transverse surface (x, y) scanning can be performed in parallel at speeds faster than video rate without physical movement of the sample. The DMD allows us to programmably configure the source and the detection pinhole array in the lateral direction to achieve the best signal and to reduce the crosstalk noise. Investigations of the microcirculation were performed on 40 g to 45 g golden Syrian hamsters fit with dorsal skin fold window chambers. FITC-Dextran or Red blood cells from donor hamsters, stained with Celltracker CM-DiI, were injected into the circulation and imaged with the confocal microscope. We will present the measured results for the axial resolution, in vivo, as well as experimental results from imaging the window chamber.

The electro-optical analog processor for discrete algorithms like the discrete Fourier transform (DFT) or filtering contains as components an LCD as picture source, a lens array for the duplication of the picture, a second LCD or a mask as multiplier and a sensor array for the addition of the results. It works with incoherent light. The components perform a massive parallel processing, the speed, bandwidth and data rate of which are discussed. The set of space discrete equations of the algorithms such as a DFT are translated into the architecture of a compact processor sized 8.5 cm in diameter and 17 cm long. The microlenses and the multiplier are clamped together tightly which renders them immune against vibrations and shocks. Examples for the DFT and for a DCT are given. The errors lie in the range of 4% to 11%, the latter for a 2-bit only processing.

We show wave front correction of a 300 fs/60J laser pulse serie. This correction is based on an optically addressed liquid crystal optical valve (OASLM) which induces high resolution phase modulations. When performed before complete thermal relaxation of the laser Nd:glass amplifiers, this correction allows to increase the system repetition rate by a factor three.

Applications of spatial light modulators to telecommunication systems are reviewed. In particular, optical cross connect (OXC) that uses 2D spatial light modulator for addressing an input beam from N input beams to a specific output fiber in N output fibers will be discussed.

Bimorph mirrors for laser beam correction and formation were developed and investigated. Different types of substrates and active piezoceramics materials were considered to fabricate temperature independent shape of the mirror surface and to maximize the sensitivity of the mirror. High reflectivity coatings for different wavelengths were studied.

An optoelectronic arbitrary-waveform generator has been proposed and experimentally developed for radar applications. It permits generating predefined waveforms by driving the amplitudes and phases of optically carried microwave signals. The optical architecture combines a high- resolution frequency shifter (for the heterodyne generation of the microwave signal) with spatial light modulators (for the parallel control of amplitudes and phases). Such a waveform generator can be attractive for target recognition or for target simulation.

A CMOS-liquid crystal-based image transceiver device (ITD) is under development at the Holon Institute of Technology. The device combines both functions of imaging and display in a single array configuration. This unique structure allows the combination of see-through, aiming, imaging and the displaying of a superposed image to be combined in a single, compact, head mounted display. The CMOS-based pixel elements are designed to provide efficient imaging in the visible range as well as driver capabilities for the overlying liquid crystal modulator. The image sensor part of the pixel is based on an n-well photodiode and a three-transistor readout circuit. The imaging function is based on a back- illuminated sensor configuration. In order to provide a high imager fill-factor, two pixel configurations are proposed: 1) A p++/p-/p-well silicon structure using twin- well CMOS process; 2) An n-well processed silicon structure with a micro-lens array. The display portion of the IT device is to be fabricated on a silicon-based reflective, active matrix driver, using nematic liquid crystal material, in LCOS technology. The timing, sequencing and control of the IT device array are designed in a pipeline array processing scheme. A preliminary prototype system and device design have been performed and the first test device is currently undergoing testing. Details of the device design as well as its Smart Goggle applications are presented.

The liquid crystal (LC) light valve, which is a spatial light modulator that uses LC material, is a very important device in the area of display development, image processing, optical computing, holograms, etc. In particular, there have been dramatic developments in the past few years in the application of the LC light valve to projectors and other display technologies. Various LC operating modes have been developed, including thin film transistors, MOS-FETs and other active matrix drive techniques to meet the requirements for higher resolution, and substantial improvements have been achieved in the performance of optical systems, resulting in brighter display images. Given this background, the number of applications for the LC light valve has greatly increased. The resolution has increased from QVGA (320 x 240) to QXGA (2048 x 1536) or even super- high resolution of eight million pixels. In the area of optical output, projectors of 600 to 13,000 lm are now available, and they are used for presentations, home theatres, electronic cinema and other diverse applications. Projectors using the LC light valve can display high- resolution images on large screens. They are now expected to be developed further as part of hyper-reality visual systems. This paper provides an overview of the needs for large-screen displays, human factors related to visual effects, the way in which LC light valves are applied to projectors, improvements in moving picture quality, and the results of the latest studies that have been made to increase the quality of images and moving images or pictures.

Micro-slits have been prepared with a slit-width and a slit- length of 2 ... 1000 micrometers . Linear and two-dimensional arrays up to 10 x 110 slits have been developed and completed with a piezo-actuator for shifting. This system is a so-called mechanical slit positioning system. The light is switched by simple one- or two-dimensional displacement of coded slit masks in a one- or two-layer architecture. The slit positioning system belongs to the transmissive class of MEMS-based spatial light modulators (SLM). It has fundamental advantages for optical contrast and also can be used in the full spectral region. Therefore transmissive versions of SLM should be a future solution. Instrument architectures based on the slit positioning system can increase the resolution by subpixel generation, the throughput by HADAMARD transform mode, or select objects for multi-object-spectroscopy. The linear slit positioning system was space qualified within an advanced micro- spectrometer. A NIR multi-object-spectrometer for the Next Generation Space Telescope (NGST) is based on a field selector for selecting objects. The field selector is a SLM, which could be implemented by a slit positioning system.