Morris, R, Jones, JC orcid.org/0000-0002-2310-0800 and Nagaraj, M orcid.org/0000-0001-9713-1362 (2020) Variable Pitch Hydrodynamic Electro-Optic Gratings Utilising Bent Liquid Crystal Dimers. Soft Matter. ISSN 1744-683X
Abstract
Electrohydrodynamic instabilities (EHDI) in liquid crystals form uniform and continuously variable diffractive structures when subject to certain material and geometry determined conditions. A one-dimensional grating is one such diffractive structure, where the refractive index changes periodically in a direction parallel to the initial liquid crystal director. The period of this structure has been shown previously to vary continuously between the values of the cell gap and half-cell gap approximately, allowing continuous angular modulation of optical beams but with a limited angular range. In this work, the lower pitch limit is shown to also be governed in part by the ratio of the splay and bend elastic constants (k11/k33) of the liquid crystal. A host nematic liquid crystal with standard elastic constant ratios (k11/k33<1) is doped with odd-alkyl-spaced dimeric liquid crystal CB7CB, to create a liquid crystal mixture with a far higher elastic constant ratio (k11/k33>5) than for those previously used in literature EHDI studies. The EHDI gratings formed in this new mixture exhibit pitch lengths significantly below half-cell gap, allowing up to 50% wider angle continuous steering of light. This improves the potential for application in beamsteering and diffractive optical devices.
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Copyright, Publisher and Additional Information: | © The Royal Society of Chemistry 2020. This is an open access article under the terms of the Creative Commons Attribution 3.0 Unported (CC BY 3.0) (https://creativecommons.org/licenses/by/3.0/) | ||||
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Institution: | The University of Leeds | ||||
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Physics and Astronomy (Leeds) > Soft Matter Physics (Leeds) | ||||
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Depositing User: | Symplectic Publications | ||||
Date Deposited: | 13 Oct 2020 10:39 | ||||
Last Modified: | 25 Jun 2023 22:27 | ||||
Status: | Published online | ||||
Publisher: | Royal Society of Chemistry | ||||
Identification Number: | https://doi.org/10.1039/d0sm01425g |