Abstract

Spatial light modulators play an important role in coherent signal processing applications, primarily as an incoherent-to-coherent light converter. In this and other applications the sensitivity and spatial resolution as well as speed are important considerations which limit performance. Reported here is a liquid crystal modulator using amorphous silicon as an ohmic photoconductor material to achieve linear modulation in a reflection mode. The thin-film layer is capable of very high resolution, >95 line pairs/mm, exceeding that of most CdS photoconductors while maintaining the high speed and broadband sensitivity of crystalline silicon. Spatial resolution of over 35 line pairs/mm has been demonstrated. The white light sensitivity is better than 20 μW/cm². A nematic liquid crystal is incorporated using both twist and birefringence mechanisms. The photoconductor consists of boron-doped amorphous silicon deposited on a glass substrate which serves as one window of the cell.

© 1986 Optical Society of America