Photo-sensitive liquid crystals for optically controlled diffraction gratings

We report on the fabrication and characterization of diffraction gratings based on a polymeric microstructure including a light responsive material, which enables an all-optical control of the diffraction of light. The enhanced performances of a mesogenic azo dye are combined with the outstanding properties of reconfigurability and fluidity of nematic liquid crystals; the mesogenic affinity between the two substances enables realization of a photosensitive liquid crystal whose optical properties can be controlled by means of low power light. Long range order and high mechanical stability of the photosensitive liquid crystal composition are obtained by using the universal organizing capability of a channeled polymeric template, without the need for any kind of surface treatment. The structure exhibits strong contrast ratio and a high diffraction efficiency, both optically controlled.