Dual photorecording on cholesteric azobenzene-containing LC polymer films using helix pitch phototuning and holographic grating recording

For the first time the possibility to perform dual recording in cholesteric LC polymer films was demonstrated by means of helix pitch photo-tuning and holographic grating recording, as far as these two photo-processes take place under the exposure to light with different wavelengths. For this purpose the cholesteric mixture of the nematic azobenzene-containing copolymer doped with the chiral-photochromic dopant was prepared and the photo-optical properties of thin planarly-oriented films of this mixture were investigated. It was found that the holographic grating recording over ∼1 min allows high diffraction efficiency values to be reached but does not disrupt the supramolecular helical structure that makes possible a two independent images recording.