Ferroelectric Spatial Light Modulator Research Articles

High-speed photorefractive joint transform correlator using nonlinear filters

A high-speed optical photorefractive correlator using a ferroelectric spatial light modulator and a new type of binary filter optimized for crystal nonlinearity is presented in terms of characteristics and performances.

Applications of FLC SLM dynamic holograms to WDM network components

This paper presents an overview of ferroelectric liquid crystal spatial light modulator (FLC SLM) dynamic digital holographic filtering technology and its application to WDM network components. Early work demonstrated a dynamically tunable filter and, in conjunction with an erbium-doped fibre amplifier (EDFA), a fibre laser[1]. The hologram design algorithm was subsequently expanded to yield a multiple variable amplitude passband filter, or spectral equaliser, for four[2] or six[3] WDM channels. Latest results for eight-channel equalisation are presented in this article, together with a demonstration of flattening the spectral shape of an individual passband. The paper concludes with a discussion of future work, including the redesign of filter parameters to meet ITU standards, and further improvements in computerised hologram design to achieve finer tuning resolution.

Efficient beam steering in the 1.55 micron window using large-tilt FLC one-dimensional array

The recent development of wavelength division multiplexing requires novel transparent optical switches with moderate reconfiguration rates (typically the ms) for management and safety requirements at the optical -wavelength- level. One important fonction in such an optical switch is beam steering in the infrared 1.55 μm region. For that purpose, we propose to design a ferroelectric liquid crystal spatial light modulator (FLC SLM) acting as a programmable diffraction grating. Futhermore, a large-tilt angle FLC is used to make the device insensitive to the polarisation of the input wavefront. Prior to the realisation of the optical swich, we present here an experimental characterisation of the FLC beam deflector.

The binary phase-only 1/f joint transform correlator

In this paper we present a new approach to implementing the joint transform correlator based on a single ferroelectric spatial light modulator used as a binary phase-only device. The correlator is a 1/f joint transform correlator which uses two passes through the optical system to generate the peaks. The input scene and reference image are encoded with a chequerboard pattern to produce a spectrum with no zero order. The spectrum is then convolutionally binarised and replayed on the spatial light modulator. Experimental results demonstrate strong correlation peaks with a zero order in the correlation plane reduced to 6dB below the correlation peaks. The correlator also demonstrates enhanced differentiation between closely correlated images.

A HOLOGRAPHICALLY ROUTED OPTICAL CROSSBAR USING A FERROELECTRIC LIQUID-CRYSTAL OVER SILICON SPATIAL LIGHT MODULATOR

Abstract Ferroelectric liquid crystal spatial light modulators can be used to display high quality binary phase holograms, and incorporated into programmable free space interconnects. These are potentially highly efficient, and have advantages over conventional shutter based architectures. Such structures have applications in telecommunications and optical processing. In this paper a 16 channel ‘crossbar’ interconnect is presented. Hologram measurement indicates the crossbar will function with a high noise margin. Device nonuniformities cause distortion in the hologram replay and techniques to compensate for this are discussed. Optical throughput and DC balancing of the liquid crystal currently restrict the performance of the switch: Possible solutions to these problems are detailed.

EDGE-ENHANCEMENT WITH FERROELECTRIC LIQUID CRYSTAL SPATIAL LIGHT MODULATORS EXPLOITING DOMAIN WALLS

Abstract Experimental evidence for edge-enhancement of images utilising domain walls between different switched states in ferroelectric liquid crystal spatial light modulator pixels is presented. Optical investigations and results using silicon backplane devices are described and discussed. The experiments use a chiral smectic C ferroelectric liquid crystal mixture with a switching angle of 45°. The effect is optimised by using a ferroelectric liquid crystal mixture with a switching angle of 90° (cone angle 45°).

Scale-invariant binary phase-only matched filter using a ferroelectric-liquid-crystal spatial light modulator

We describe the implementation of a scale-invariant binary phase-only matched filter using a 128 × 128 ferroelectric spatial light modulator. A 5-dB discrimination was obtained between a 10-image training set of highly correlated characters (E's and F's) over a scale range of 1.0 to 1.5.

Dynamic asymmetric binary holograms using a ferroelectric liquid crystal spatial light modulator

The implementation of asymmetric binary phase holograms using a 128 × 128 ferroelectric spatial light modulator is describe. The symmetry is broken by providing a pseudo four-level phase system. A pixellated diffractive element is inserted in series with a binary phase spatial light modulator, generating enough phase freedom to break the symmetry. The diffractive element is constructed by etching photoresist spun onto an optically flat glass substrate. Experimental results are presented, with the symmetric order being suppressed by a minimum of 9.7 dB.

Dynamic holographic interconnects that use ferroelectric liquid-crystal spatial light modulators

<p>Dynamic interconnect holograms are designed by the use of a simulated annealing algorithm and written to a 128 × 128 pixel ferroelectric spatial light modulator that is used in a binary-phase mode. Dynamic holograms are used to implement a 2 × 2 crossbar with single-mode fiber inputs and outputs, which function with as high as 27 dB of isolation between output ports. The principle is extended to two-dimensional interconnection holograms, and arbitrary fan-out to as high as 64 points is demonstrated with good performance.</p><p>Images of interconnection holograms are transferred from the spatial light modulator to an optically addressed spatial light modulator that is used in a binary-phase mode. The addition of a fixed array generator computer-generated hologram permits replication of the hologram image, thus creating a larger hologram with a high space-bandwidth product on the optically addressed spatial light modulator.</p><p>Results of a preliminary experiment are presented.</p>

Ferroelectric liquid crystal spatial light modulators and their applications

Abstract This paper describes optically-addressed spatial light modulators (OASLM) employing ferroelectric liquid crystals (FLC) and their applications. By exploiting the bistability in the FLC, the OASLM can output both positive and negative images and store them. Fast switching and high resolution make these devices useful for many applications, including image processing and real-time holography.

Parallel access read/write memory using an optically addressed ferroelectric spatial light modulator

The ability is demonstrated to use optically addressed ferroelectric spatial light modulators in designing digital optical computers involving data processing and storage athigh rates and contrast levels. Key words: Bistability, ferroelectric SLM, parallel access memory.