Ferroelectric light valve arrays for optical memories

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Abstract
An array of electrically addressed light valves, referred to as a page composer or a pattern generator, is an important component of an optical memory. Ferroelectric and related materials, such as nematic liquid crystals, are attractive candidates for this application. This paper details the geometrical and optical characteristics and the various techniques for addressing a page composer for a holographic optical memory. Experimental data obtained on a nematic liquid crystal and single crystal bismuth titanate are presented. This data is compared with that previously reported for ceramic lead zirconate titanate and single crystal gadolinium molybdate. The major conclusions are that the optimum array is one in which the valves are individually addressed light scatterers. This operating mode is most conveniently achieved with a liquid crystal on an integrated semiconductor chip. The semiconductor circuits can also serve as the photodetector array for the optical memory. However, slow switching limits the usefulness of the liquid crystal page composer. At the present time matrix addressed variable birefringent bismuth titanate is the most promising material. Fabrication of such an array is, however, difficult.

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