Real-time holographic investigation of azo dye diffusion in a nematic liquid crystal host

The diffusion anisotropy of C.I. Disperse Red 1 (2-(ethyl(4-((4-nitrophenyl)azo)phenyl)amino)ethanol), in a nematic liquid crystal mixture (1294-1b) was studied using real-time diffraction-monitoring. The trans-cis photoisomerization of the dye molecules and the diffusion of photoexcited isomers were identified as essential components in the mechanisms of grating formation and relaxation, respectively. The results were used to investigate the diffusion parameters of dye molecules in both parallel and perpendicular directions to the director.