Periodic defects lines in liquid crystal cell guided by polarization holograms at an aligning surface

Abstract

Defect lines arrays are created in liquid crystal exploiting periodic arrangements of twisted domains with opposite handedness. The defect lines self-organize in a planar cell guided by a polarization hologram recorded in one aligning substrate that provides planar periodic alignment. Depending on the relationship between the cell thickness d and the hologram pitch Λ, the array period can be either Λ or 2Λ. An external voltage enables to switch the spatial periodicity of the defect lines from 2Λ to Λ and also to control their shape and location. A modeling of the observed twisted arrangements is reported.

Light manipulation of nanoparticles in arrays of topological defects

“…The second and third cells, generating 1D and 2D periodic patterns of QDs lines, are assembled using one unidirectional orienting substrate and a second substrate covered with a polarization-sensitive azo-dye film 38 . Exploiting polarization holographic recording in combination with the photoaligning command substrates, the opposite-sign twist configuration is realized periodically, thus providing the condition for properly designed TD arrays.…”

“…1D periodic parallel QDs-rich TD lines of the same kind described before (singular core, S = 1/2) are produced with a spatial periodicity of 16 µm. Figure 4a,b show the bright-field microscope images, before and after the blue LED illumination of the chiral NLC/QDs layer confined between an unidirectional planar aligning substrate and a periodic planar photo-aligning substrate, providing periodically modulated alignment direction 38 (see video 2 in the supplementary information ). The corresponding confocal fluorescence microscope images are represented in Fig.…”

“…The spacers between glasses provided a cell thickness of 20 μm, while the transversal dimensions of the cell are 2 cm × 3 cm. The second and third devices, generating 1D and 2D arrays of TD lines, have been obtained using one unidirectional orienting substrate and a second substrate with a tens of nm thick polarization sensitive azo-dye film able to provide holograms-designed anchoring condition 38 . The photo-aligning patterns have been generated exploiting polarization holographic recording with two different schemes.…”