Polarization Gratings in Azobenzene-Based Fully Liquid Crystalline Triblock Copolymer

Photosensitive liquid crystalline (LC) block copolymers are a universal platform for designing functional materials for optics and photonics. Here, azobenzene LC ABA triblock copolymer containing mesogenic groups in each block is studied as a medium for the recording of polarization holographic gratings. The fast recording of polarization gratings is successfully performed with two orthogonally circularly polarized light beams of a 532-nm laser. It is shown that annealing of the recorded polarization grating increases diffraction efficiency considerably, by a factor of 70, and provokes simultaneous erasing of the surface relief grating if it has been recorded. Holographic behavior of the triblock copolymer is compared with that of an azobenzene homopolymer and a random copolymer, which has the same monomer ratio as the triblock copolymer. The obtained results are expected to allow designing new materials for the polarization of optical elements and holographic data storage.