Optical phase conjugation from phase-shifted gratings in photorefractive mesogenic composites

Optical phase conjugation has been observed from non-local gratings generated in a photorefractive mesogenic composite consisting of a low-molar-mass nematic mixture, a functionalized copolymer and a photoconductive sensitizer. The degenerate four-wave mixing experiment enabled measurements of phase conjugate reflectance as a function of the intensity ratio of the forward and backward pump beams. The characteristics were strongly dependent on the spatial phase shift; these results are quantitatively explained by the coupled wave theory in relation to non-local gratings.