Ferroelectric Liquid Crystal Over Silicon Spatial Light Modulators - Principles, Practice and Prospects

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The hybrid technology which combines a thin layer of ferroelectric liquid crystal directly on top of a CMOS backplane has provided a hybrid technology for spatial light modulators which has already reached a mature stage of development. Devices of around 10 6 pixels are under construction. The use of devices in a number of systems has already been demonstrated. Key words spatial light modulators head-up displays optical data processing liquid crystal devices 1 Introduction A spatial light modulator (SLM) is a device capable of impressing information onto an optical wavefront. SLMs exist in many forms [1]. Light modulation may be carried out by electro-optic, acousto-optic and mechanical effects, among others. A SLM may be addressed optically, acoustically, electrically, electronically or by electron beam. The applications of such devices are manifold and include information display, coherent optical data processing, data routing and holography. The overall field of SLMs has been...

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    • "Liquid crystal devices (LCDs) have become attractive for practical applications such as diffractive optics, adaptive optics, or optical metrology [1] [2] [3]. LCDs based on ferroelectric liquid crystals (FLCs) are of particular interest because of their very fast frame rates (several kilohertz) and highly efficient electro-optic effect [4] [5] [6]. Single-pixel FLC modulators have found applications such as optical switches [7], tunable filters [8], optical rotators [9], and phase shifters [10]. "
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    ABSTRACT: The Poincaré sphere representation is used to analyze the polarization transformation achieved with a ferroelectric liquid crystal (FLC) optical modulator. This device acts as a switchable wave-plate, in which the orientation of the principal axes rotates under the action of an applied bipolar voltage. In the standard operational mode for intensity switching, the rotation angle of the principal axes is θ = π/4 and the phase shift is φ = π (half-wave-plate). However, for wavelengths different from the design one, the FLC deviates from the half-wave-plate performance and the optical contrast is diminished. We use the Poincaré sphere representation to perform a theoretical analysis of the intensity switch performance of the FLC modulator as a function of the phase shift φ. Using spherical trigonometric relations we derive analytical expressions for the intensity contrast as a function of φ and we show how to compensate its decrease when φ = π by using appropriate elliptically polarized illumination. These situations are experimentally demonstrated using a commercially available FLC cell.
    Full-text · Article · Jan 2009 · Journal of Optics A Pure and Applied Optics
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    ABSTRACT: Das Ziel der Arbeit ist die Konzeption, der Aufbau und die Validierung eines neuartigen, flexiblen und kostengünstigen optischen Oberflächen-Messsystems mit einer Auflösung im Sub-Mikrometer-Bereich u.a. zur Inspektion von Mikrostrukturen. Kernpunkt ist dabei die Sonderanwendung der für die digitale Bildprojektion eingesetzten Mikrospiegelmatrix „Digital Micromirror Device” (DMD) des US-amerikanischen Halbleiterherstellers Texas Instruments. Das hierbei entwickelte Messsystem lässt Ähnlichkeiten zu Autofokusverfahren und konfokaler Mikroskopie erkennen, ersetzt jedoch die klassischen lateralen Abtastsysteme, wie beispielsweise die heute weit verbreitete rotierende Nipkow-Scheibe, die aus einer Vielzahl spiralförmig angeordneter Lochblenden besteht, durch den DMD. Die Arbeit beschreibt die grundlegende Funktionsweise des entwickelten Messsystems unter besonderer Betrachtung des optischen Aufbaus und der Funktion des DMD als laterales optisches Abtastinstrument. Im Speziellen wird dabei erläutert, welche prinzipiellen Verfahren zur Gewinnung von 3D-Höheninformationen angewandt werden, wie mit Rauschen umgegangen wird, welche Interpolationsstrategien herangezogen werden können und wie unsichere Messpunkte erkannt werden. Ferner stellt sie den Einfluss optischer Phänomene dar, die auf den Einsatz des DMD zurückzuführen sind. Abschließend werden exemplarisch einige Topographie-Messergebnisse des Systems präsentiert und weitere Einsatzmöglichkeiten demonstriert. Mit dem vorgestellten DMD-basierten Messsystem lassen sich Oberflächenprofile mit lateralen Ausdehnungen zwischen 73µm x 73µm und 730µm x 730µm mit einer vertikalen Auflösung von bis zu rund 20 nm optisch messen. The goal of the work is the conception, design and validation of a new, flexible and low-priced optical surface measuring system with a resolution in the submicrometer range, i.e. for the inspection of microstructures. Quintessential point is the application of semiconductor-manufacturer Texas Instruments digital micromirror device (DMD). The developed measuring system shows similarities to autofocus methods and confocal microscopy, however, replacing the classical lateral scanning systems, as for example the wide-spread rotating Nipkow disk, which consists of a number of pinholes arranged in spirals, by the DMD. The work describes the fundamental functionality of the developed measuring system with special respect to the optical system design and the use of the DMD as lateral optical scanning instrument. It is specifically described, which principle procedures are used for the reproduction of the measured 3D-topography, how noise is handled, which interpolation strategies can be applied, how uncertain measuring points are recognized and which optical effects arise from the use of the DMD. Finally, some topography measurement-results obtained from the system are presented and further applications are demonstrated. With the presented DMD-based measuring system surfaces with lateral expansions between 73µm x 73µm and 730µm x 730µm can be measured optically with a vertical resolution of up to approximately 20 nm.
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    ABSTRACT: FLC/VLSI spatial light modulators (SLMs) offer a means of implementing programmable holograms. The pixel described here offers advantages over those previously used and has the potential to be implemented in a large array. We give an initial description of a pixel which allows one of four levels of (highly stable) voltage to be driven onto the pixel mirror thus allowing four els of phase to be generated. This provides the advantages of static memory drive with those of four level phase modulation, albeit at the expense of circuit complexity
    No preview · Conference Paper · Aug 1998
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