Real-time observation of liquid crystal molecular directions based on a snapshot polarimeter

Jing Ma; Canhua Xu; Yangguang Yao

doi:10.3788/COL201715.061601

Journals >Chinese Optics Letters >Volume 15 >Issue 6 >Page 061601 > Article

Chinese Optics Letters
Vol. 15, Issue 6, 061601 (2017)

Real-time observation of liquid crystal molecular directions based on a snapshot polarimeter

Jing Ma¹, Canhua Xu^1、*, and Yangguang Yao²

Author Affiliations

¹College of Physics and Information Engineering, Fuzhou University, Fuzhou 350002, China

²College of Mathematics and Computer Science, Fuzhou University, Fuzhou 350002, China

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DOI: 10.3788/COL201715.061601 Cite this Article Set citation alerts

Jing Ma, Canhua Xu, Yangguang Yao. Real-time observation of liquid crystal molecular directions based on a snapshot polarimeter[J]. Chinese Optics Letters, 2017, 15(6): 061601 Copy Citation Text

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Abstract

The polarization state of transmitted light is linked to liquid crystal (LC) molecular distribution. The dynamic behavior of a twisted nematic LC molecule is measured with a home-built 10 kHz snapshot polarimeter. Only the transient molecule rotations are observed when the external voltage changes, and the molecules return to their original orientations quickly even when high voltage is applied. Our observations cannot be attributed to the traditional electro-optic effect. The invalidation of the static external field indicates the shielding effect of redistributing impurity ions in an LC cell.

Δ n (θ) = \frac{n_{e} n_{o}}{\sqrt{n_{e}^{2} \cos^{2} θ + n_{o}^{2} \sin^{2} θ}} - n_{o},

(1)

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R = \frac{2 π Δ n (θ) d}{λ_{0}},

(2)

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\tan 2 φ = \tan 2 ψ \cos R .

(3)

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δ (y) = \frac{2 π}{λ} (n_{e} - n_{o}) y \cdot \tan α,

(4)

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A_{0} = [\begin{matrix} \cos ψ \\ \sin ψ \cdot e^{i R} \end{matrix}],

(5)

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M_{cy} = [\begin{matrix} 1 & 0 \\ 0 & e^{i δ (y)} \end{matrix}] .

(6)

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I_{1} = \frac{1}{2} [1 + \sin 2 ψ \cos (δ + R)] .

(7)

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I_{2} = \frac{1}{2} (1 + \sin 2 ψ \cos R \cos δ - \cos 2 ψ \sin δ) .

(8)

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I_{2} = \frac{1}{2} [1 + (\cos 2 ψ / \cos 2 φ) \cdot \sin (2 φ + δ)] .

(9)

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Jing Ma, Canhua Xu, Yangguang Yao. Real-time observation of liquid crystal molecular directions based on a snapshot polarimeter[J]. Chinese Optics Letters, 2017, 15(6): 061601

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