An ac-operated liquid-crystal light valve has been constructed and operated. The multilayer structure, consisting of a photoconductor, light-absorbing layer, dielectric mirror, and liquid crystal, is capable of efficiently modulating a high-intensity light beam with a comparatively weak light source. The dielectric mirror and absorbing layer provide high reflectance and optical isolation without the use of a metal mosaic reflector. The use of ac and insulated electrodes promises long lifetime. The light valve is applicable to television projection display and optical data processing.

Absorption measurements of liquid crystals in the ultraviolet, visible, and infrared

Photoactivated electric field effects in nematic liquid crystals serve as reversible nearly real-time techniques for recording phase-type holograms. In a sandwich-type cell, a photoconductive coating separates one conductive electrode from the liquid-crystal layer, which is operated below the threshold voltage for dynamic scattering. In CdS cells, transient first-order diffraction efficiencies of 10–30% are obtained within 0.1–0.2 sec from visible light exposures of less than 1 μJ/cm2. A 10-μW/cm2 Ar-ion laser interference pattern of 40 cycle/mm produced a steady-state first-order diffraction efficiency of 8% in a 13-μm thickness of MBBA in a cell operated at 4-V dc. Resolutions up to 100 cycle/mm are observed for this thickness of liquid crystal.

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