Fast optical recording of polarization holographic grating based on an azo-dye-doped polymer-ball-type polymer-dispersed liquid crystal film

This work reports a fast optical recording material based on an azo-dye-doped polymer-ball-type polymer-dispersed liquid crystal film. A memory polarization holographic grating is written on the film and formed in ∼2 ms using two writing beams derived from a Q-switched Nd:YAG SHG pulse laser (λ_w = 532 nm) with duration of 20 ns and a total energy density of ∼15 mJ/cm². The polarization grating (PG) is created from the photo-excited dye molecules. These photo-excited dye molecules undergo three-dimensional rotation, diffusion, then adsorb on the surface of the polymer balls, and finally induce the reorientation of the LCs. Polarization analysis of the PG reveals that it diffracts the linearly polarized incident light into beams with different polarizations. A model based on the Jones matrix method is also proposed and closely fits the experiment results. Experimental results indicate that the PG is electrically switched (∼3 V/μm). The PG can be erased partially by thermal treatment. We speculate that the weakly-adsorbed dyes desorb from the surfaces of the polymer balls owing to thermal disturbance, causing partial grating erasion.