High‐speed light valve using an amorphous silicon photosensor and ferroelectric liquid crystals

A novel high‐speed response light valve composed of a hydrogenated amorphous silicon (a‐Si:H) photosensor and a chiral smectic C phase liquid crystal is presented for the first time. This device is optically addressed. The switching between on and off states is caused by reversing the polarity of the applied voltage across the liquid crystal due to the photocurrent from the a‐Si photosensor. The response time measured is about 400 μs. The switching speed of this device is one to two orders of magnitude faster than that of the nematic liquid‐crystal light valve. This device can be applied to optical bistable devices without optical feedback, using an electro‐optic memory effect of the ferroelectric liquid crystal.