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Confined photovoltaic fields in a photo-responsive liquid crystal test cell
Author(s): Atefeh Habibpourmoghadam; Lin Jiao; Faissal Omairat; Dean R. Evans; Liana Lucchetti; Viktor Reshetnyak; Alexander Lorenz
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Paper Abstract

Exciting experimental results on the response properties of hybridized photo responsive liquid crystal test cells are reported, where iron doped lithium niobate substrates were used to photo generate electric fields and indium tin oxide coated cover glasses were used to confine these photo generated fields in a liquid crystal layer. Samples were investigated in a modified inverted optical polarizing microscope with white probe light (crossed polarizers) and exposed with a Gaussian laser beam focused to a small spot (14 μm FWHM). Test cells filled with nematic LC showed homeotropic director alignment. Upon exposure, this alignment was maintained at the exposure spot center and the LC director was selectively realigned in a surrounding single ring. This ring had a thickness of a few microns and its diameter increased with increasing exposure intensity (112 μm at 0.7 mW, 204 μm at 1.1 mW). This characteristic director realignment was traced back to the optically generated electric field distributions by simulations. In samples filled with chiral nematic LC, uniformly standing helix alignment was found. Textural transitions were induced at the focus position, which again led to the formation of well-defined circular defects. We could show that these defects can be permanently stored within the chiral nematic LC. Polarized optical microscopy of a rotated sample revealed that a point like defect with +1 topological charge was enclosed in each of these defects. Photovoltaic fields generated in small lithium niobate particles dispersed in a LC were found to cause promising optical responses and particle movement.

Paper Details

Date Published: 25 August 2017
PDF: 11 pages
Proc. SPIE 10361, Liquid Crystals XXI, 1036112 (25 August 2017); doi: 10.1117/12.2273990
Show Author Affiliations
Atefeh Habibpourmoghadam, Univ. Paderborn (Germany)
Lin Jiao, Univ. Paderborn (Germany)
Faissal Omairat, Univ. Paderborn (Germany)
Dean R. Evans, Air Force Research Lab. (United States)
Liana Lucchetti, Univ. Politecnica delle Marche (Italy)
Viktor Reshetnyak, Taras Shevchenko National Univ. of Kyiv (United Arab Emirates)
Alexander Lorenz, Univ. Paderborn (Germany)
Univ. of Kassel (Germany)


Published in SPIE Proceedings Vol. 10361:
Liquid Crystals XXI
Iam Choon Khoo, Editor(s)

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