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Rewritable Liquid Crystal Gratings Fabricated Using Photoalignment Effect in Dye-Doped Poly(vinyl alcohol) Film

In this paper, we present rewritable liquid crystal (LC) gratings based on azo dye-doped polyvinyl alcohol films. The mechanism of such rewritable characteristics is attributable to the irradiation of these films with a suitable linearly polarized light beam which reorients dyes and then aligns LCs. Two gratings, one with a 90° twist nematic (TN)/homogeneous periodical alignment and the other with a 45° TN/-45° TN reversely twisted periodical alignment, are fabricated. The polarizations of the beams diffracted from these two gratings are studied. A single model using the Jones matrix representation is formulated and used to analyze these two gratings. Experimental results are consistent with theoretical results and show that the gratings can be used as polarization beam splitters and are electrically switchable.