DIFFRACTiVE LIQUID CRYSTAL SPATIAL LIGHT MODULATORS WITH OPTICALLY INTEGRATED FINE-PITCH PHASE GRATINGS

We describe opto-electronic LC spatial light modulators which allow the generation of alterable diffraction gratings down to 1 micrometers period. Optically defined binary and blazed phase gratings are used in which the diffraction is altered by a parallel aligned nematic LC phase modulation layer. This enables the creation of arbitrary fine-pitch gratings. Different types of modulators have been theoretically and experimentally investigated. The theoretical results show that in the case of small grating structures the exact wave theory has to be applied to calculate the diffraction properties. Then the grating modulation becomes dependent on the light polarization and the grating period. Modulators with gratings of 1 to 10 micrometers period have been fabricated. The modulator structure, the LC phase modulation layer, the problems of combining LCs with fine-pitch gratings, and the modulator properties are discussed. Good diffraction efficiencies and extinction ratios for the diffraction orders of the modulators for monochromatic light have been obtained as well as short switching times.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.