Photoalignment control of liquid crystals on photo-cross-linkable polymer liquid crystal film and its application to polarization gratings

Nobuhiro Kawatsuki; Masaomi Kuwabara; Yasushi Matsuura; Tomoyuki Sasaki; Hiroshi Ono

doi:10.1117/12.618853

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20 August 2005 Photoalignment control of liquid crystals on photo-cross-linkable polymer liquid crystal film and its application to polarization gratings

Nobuhiro Kawatsuki, Masaomi Kuwabara, Yasushi Matsuura, Tomoyuki Sasaki, Hiroshi Ono

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Proceedings Volume 5936, Liquid Crystals IX; 593608 (2005) https://doi.org/10.1117/12.618853
Event: Optics and Photonics 2005, 2005, San Diego, California, United States

Abstract

Photoinduced reorientation of a copolymer liquid crystal (CPLC) and an alignment behavior of low-molecular-weight liquid crystals (LCs) on the resultant film are described. Adjusting the exposure energy of a linearly polarized ultraviolet (LPUV) light and the subsequent annealing control the reorientation direction of copolymer films both perpendicular and parallel to the polarization (E) of LPUV light, and the LCs align along the reorientation direction of the mesogenic groups of the CPLC film. In contrast, LCs align perpendicular to E of the LPUV light regardless of the exposure doses when using a copolymer film without annealing because non-reacted mesogenic groups control the alignment of the LC molecules. When the fabricated LC cell is annealed near the glass transition temperature of the CPLC film, the LC alignment behavior changes similar to that using the annealed film, where the reorientation of the mesogenic groups of the alignment layer in contact with the LC materials is generated. Since the LC alignment direction can be controlled both parallel and perpendicular to E, a new type of pure polarization grating with periodical LC alignment direction is demonstrated using a LC cell. The conversion of the polarization of diffracted light beams as well as a transmitted light beam is observed and the diffraction efficiency is 18%. These optical properties of the polarization grating exhibit a good agreement with the theoretical calculation.

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Nobuhiro Kawatsuki, Masaomi Kuwabara, Yasushi Matsuura, Tomoyuki Sasaki, and Hiroshi Ono "Photoalignment control of liquid crystals on photo-cross-linkable polymer liquid crystal film and its application to polarization gratings", Proc. SPIE 5936, Liquid Crystals IX, 593608 (20 August 2005); https://doi.org/10.1117/12.618853

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