High-speed optically-addressed spatial light modulator

High-speed optically-addressed spatial light modulators (OASLMs) have been designed, fabricated, and tested. The response time of these devices, in which a ferroelectric liquid-crystal (FLC) is incorporated as the modulating layer, can be substantially faster than that of OASLMs using nematic liquid crystals. A p-i-n structure of hydrogenated amorphous silicon (a-Si:H), which forms the photosensor, has response times, resolution, and mechanical properties that are compatible with the FLC. Two ranges of response times to write beam illumination, below and above approximately 100 ms, have been observed in the OASLM devices. The longer times appear to result from the photoconductivity of the highly resistive i-layer of the photodiode. Under chopped illumination the photoconductivity is averaged out, so that the photocurrent produced during the negative bias segment of the cycle produces the shorter response time optical modulation