Director grating and two-beam energy exchange in a hybrid photorefractive cholesteric cell with a helicoidal polymer network

We develop a theory describing two-beam energy exchange in a cholesteric liquid crystal (CLC) stabilized in the planar state by a helicoidal polymer network. The CLC layer is placed between photorefractive and non-photorefractive substrates and illuminated by two intersecting coherent light beams. A...

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Bibliographic Details
Published in:Journal of applied physics 2020-03, Vol.127 (12)
Main Authors: Reshetnyak, V. Yu, Pinkevych, I. P., McConney, M. E., Evans, D. R.
Format: Article
Language:English
Subjects:
Applied physics
Cholesteric liquid crystals
Coherent light
Electric fields
Exchanging
Light
Light beams
Mathematical analysis
Photorefractivity
Polymers
Substrates
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Summary:We develop a theory describing two-beam energy exchange in a cholesteric liquid crystal (CLC) stabilized in the planar state by a helicoidal polymer network. The CLC layer is placed between photorefractive and non-photorefractive substrates and illuminated by two intersecting coherent light beams. An interference pattern created by the incident beams induces a spatially periodic space-charge electric field in the photorefractive substrate. The field penetrates into the adjacent CLC layer and interacts with the charges trapped on the polymer fibrils forcing the fibrils to move along the helicoidal axis. At new positions, the fibrils reorient the CLC director and, therefore, induce a director grating. The light beams propagating across the cell couple within the grating. We calculate the energy exchange between the coupled beams and the gain of the weak light beam. We analyze the dependence of the gain coefficient on the parameters of the polymer network and the CLC and show that it can reach values greater than those obtained in typical solid photorefractive crystals.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.5142079