A high‐speed optically addressed spatial light modulator is described which uses the electroclinic effect in chiral smecticAliquid crystals with ap‐i‐nphotodiode of hydrogenated amorphous silicon (a‐Si:H). The near microsecond response time is a function of the liquid‐crystal mixture and temperature. We present and analyze optical modulation measurements of a device which exhibits a response time of 40 &mgr;s at 29 °C and 4 &mgr;s at 50 °C. The optical response is continuous and linear with electric field and write‐light intensity, allowing for grey level applications.