Advances in optical writing on nematic azobenzene polymers: relaxation processes and length scales

The possibility of achieving devices for rewritable optical storage is provided by polymers with azobenzene side groups, because they undergo photochemically induced trans-cis reversible isomerization. Main crucial parameters in data storage are bit stability, homogeneity at molecular level, and working temperature range. In this work we overview our investigations into liquid crystalline, nematic PMA4 homopolymers and copolymers of a side group azobenzene methacrylate, as candidate materials for optical nanowriting. Relaxation processes over different timelength scales are discussed with particular reference to understanding the interplay between homogeneity at the molecular level, bit stability and working temperature range. We emphasize the significance of conformational rearrangements of the polymer chain backbone in stabilizing structurally homogeneous substrates. Suitability of topography and birefringence writings is illustrated with examples of imprinted information at the nanometer scale.