Operating Characteristics of Optically Addressed Spatial Light Modulators Incorporating Distorted Helix Ferroelectric Liquid Crystals

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Abstract
Distorted helix ferroelectric liquid crystals have received attention recently due to the availability of short-pitch, high-spontaneous-polarization mixtures. In this paper we discuss the operating characteristics of an optically addressed spatial light modulator incorporating a hydrogenated amorphous silicon photosensor and a distorted-helix ferroelectric liquid crystal light modulator. The device exhibits a grey-scale response over a range of write-light intensities which depends on operating frequency. The spatial resolution is 30 lp/mm. The time-averaged contrast ratio is 7:1, limited primarily by non-uniformity in the liquid crystal alignment. During switching, both the average optic axis orientation and the effective birefringence of the liquid crystal change. The capability of the device to produce a pseudocolored readout image is attributed to the latter effect.