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Two-beam energy exchange in a hybrid photorefractive-flexoelectric liquid-crystal cell

Two-beam energy exchange in a hybrid photorefractive-flexoelectric liquid-crystal cell
Two-beam energy exchange in a hybrid photorefractive-flexoelectric liquid-crystal cell
We develop a semiquantitative theory to describe the experimentally observed energy gain when two light beams intersect in hybrid organic-inorganic photorefractives. These systems consist of a nematic liquid-crystal LC layer placed between two photorefractive windows. A periodic space-charge field is induced by the interfering light beams in the photorefractive windows. The field penetrates into the LC, interacting with the nematic director and giving rise to a diffraction grating. LC flexoelectricity is the principal physical mechanism driving the grating structure. Each light beam diffracts from the induced grating, leading to an apparent energy gain and loss within each beam. The LC optics is described in the Bragg regime. In the theory the exponential gain coefficient is a product of a beam interference term, a flexoelectricity term and a space-charge term. The theory has been compared with results of an experimental study on hybrid cells filled with the LC mixture TL 205. Experimentally the energy gain is maximal at much lower grating wave numbers than is predicted by naïve theory. However, if the director reorientation is cubic rather than linear in the space-charge field term, then good agreement between theory and experiment can be achieved using only a single fitting parameter. We provide a semiquantitative argument to justify this nonlinearity in terms of electric-field-induced local phase separation between different components of the liquid crystal.
liquid crystals, photorefraction, non-linear optics
1539-3755
31705
Reshetnyak, V.Yu.
1443c2dd-2066-4dd6-ae18-f3b408dea98d
Pinkevych, I.P.
07f566ed-7a1c-492d-a11e-3ff1e941e725
Cook, G.
fbf121a4-8973-4033-8759-81f517347b6e
Evans, D.R.
e53d4df7-2a26-49f0-8126-b6630165dfb3
Sluckin, T.J.
8dbb6b08-7034-4ae2-aa65-6b80072202f6
Reshetnyak, V.Yu.
1443c2dd-2066-4dd6-ae18-f3b408dea98d
Pinkevych, I.P.
07f566ed-7a1c-492d-a11e-3ff1e941e725
Cook, G.
fbf121a4-8973-4033-8759-81f517347b6e
Evans, D.R.
e53d4df7-2a26-49f0-8126-b6630165dfb3
Sluckin, T.J.
8dbb6b08-7034-4ae2-aa65-6b80072202f6

Reshetnyak, V.Yu., Pinkevych, I.P., Cook, G., Evans, D.R. and Sluckin, T.J. (2010) Two-beam energy exchange in a hybrid photorefractive-flexoelectric liquid-crystal cell. Physical Review E, 81 (3), 31705. (doi:10.1103/PhysRevE.81.031705).

Record type: Article

Abstract

We develop a semiquantitative theory to describe the experimentally observed energy gain when two light beams intersect in hybrid organic-inorganic photorefractives. These systems consist of a nematic liquid-crystal LC layer placed between two photorefractive windows. A periodic space-charge field is induced by the interfering light beams in the photorefractive windows. The field penetrates into the LC, interacting with the nematic director and giving rise to a diffraction grating. LC flexoelectricity is the principal physical mechanism driving the grating structure. Each light beam diffracts from the induced grating, leading to an apparent energy gain and loss within each beam. The LC optics is described in the Bragg regime. In the theory the exponential gain coefficient is a product of a beam interference term, a flexoelectricity term and a space-charge term. The theory has been compared with results of an experimental study on hybrid cells filled with the LC mixture TL 205. Experimentally the energy gain is maximal at much lower grating wave numbers than is predicted by naïve theory. However, if the director reorientation is cubic rather than linear in the space-charge field term, then good agreement between theory and experiment can be achieved using only a single fitting parameter. We provide a semiquantitative argument to justify this nonlinearity in terms of electric-field-induced local phase separation between different components of the liquid crystal.

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More information

Published date: 17 March 2010
Keywords: liquid crystals, photorefraction, non-linear optics

Identifiers

Local EPrints ID: 79828
URI: http://eprints.soton.ac.uk/id/eprint/79828
ISSN: 1539-3755
PURE UUID: 53b1cc13-b328-425e-afb5-161f627a017b
ORCID for T.J. Sluckin: ORCID iD orcid.org/0000-0002-9163-0061

Catalogue record

Date deposited: 22 Mar 2010
Last modified: 09 Jan 2022 02:32

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Contributors

Author: V.Yu. Reshetnyak
Author: I.P. Pinkevych
Author: G. Cook
Author: D.R. Evans
Author: T.J. Sluckin ORCID iD

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