Dynamic polarization grating based on a dye-doped liquid crystal controllable by a single beam in a homeotropic-planar geometry

We present a dynamic polarization grating based on a dye-doped liquid crystal cell that is controllable by a single pump beam in a binary homeotropic-planar configuration produced through selective rubbing. Upon single pump beam irradiation, the azo dyes in the liquid-crystal (LC) layer diffuse and adsorb onto the planar LC-anchoring surface due to trans-cis photo-isomerization. It is found that the dynamic polarization grating effect results mainly from the photo-induced easy axis reorientation by the amount of dye molecules adsorbed on the planar LC-alignment surface in a single-beam control scheme. The initial LC-anchoring conditions and the dynamic behavior of the dye adsorption strongly influence the repetitive writing-erasing processes by the single pump beam.