Measurement of helical twisting power based on axially symmetrical photo-aligned dye-doped liquid crystal film

Ko, Shih-Wei; Huang, Shu-Chien; Fuh, Andy Ying–Guey; Lin, Tsung‐Hsien

doi:10.1364/oe.17.015926

Cited by 27 publications

(15 citation statements)

References 13 publications

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“…According to the Bragg reflection, the effective pitch length of each N*LC cell can be obtained, 300.6 nm for blue N*LC cells, 337.5 nm for green, and 434.4 nm for red. In addition, based on the reduced equation of HTP [51], which is equal to the inverse of the product of the pitch length and chiral dopant concentration labeled in Fig. 2(b), the experimental value is close to the theoretical one (10.…”

Section: Resultssupporting

confidence: 61%

Effects of chiral dopant on electro-optical properties of nematic liquid crystal cells under in-plane switching and non-uniform vertical electric fields

Lin¹,

Chen²,

Lin³

et al. 2014

Opt. Mater. Express

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The electro-optical properties of the chiral nematic liquid crystal cell, driven by in-plane switching and non-uniform vertical electric fields, are investigated. The Bragg reflection, threshold voltage, and helical configuration are significantly related with the chiral dopant concentration. Through the driving-mode switching, two bistable helical structures without holding voltages are developed. The behavior of voltage-and temperaturedependent light reflection associated with the helical structure transition is also revealed. A fast bistable switching response (~5 ms) is successfully achieved by the three-terminal-electrode architecture. Further, the proposed cell shows a display time of over 6 hr in the unplugged power state.

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Section: Resultssupporting

confidence: 61%

Effects of chiral dopant on electro-optical properties of nematic liquid crystal cells under in-plane switching and non-uniform vertical electric fields

Lin¹,

Chen²,

Lin³

et al. 2014

Opt. Mater. Express

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“…The CLC phase is composed of a mixture of 4-cyano-4'-pentylbiphenyl (5CB), nematic at room temperature, and a chiral dopant (S)-4-cyano-4-(2-methylbutyl)biphenyl (CB15). The pitch p is determined by the amount of dopant present in the solution [28]. The thickness of the shell can be kinetically tuned via osmotic annealing [25,29]: increasing the molar salt concentration in one of the aqueous phases creates an osmotic pressure difference through the CLC shell, resulting in a flux of water across the permeable shell.…”

Section: Modulating Anchoring At Liquid Crystal Interfacesmentioning

confidence: 99%

Change in Stripes for Cholesteric Shells via Anchoring in Moderation

et al. 2017

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Chirality, ubiquitous in complex biological systems, can be controlled and quantified in synthetic materials such as cholesteric liquid crystal (CLC) systems. In this work, we study spherical shells of CLC under weak anchoring conditions. We induce anchoring transitions at the inner and outer boundaries using two independent methods: by changing the surfactant concentration or by raising the temperature close to the clearing point. The shell confinement leads to new states and associated surface structures: a state where large stripes on the shell can be filled with smaller, perpendicular substripes, and a focal conic domain (FCD) state, where thin stripes wrap into at least two, topologically required, double spirals. Focusing on the latter state, we use a Landau-de Gennes model of the CLC to simulate its detailed configurations as a function of anchoring strength. By abruptly changing the topological constraints on the shell, we are able to study the interconversion between director defects and pitch defects, a phenomenon usually restricted by the complexity of the cholesteric phase. This work extends the knowledge of cholesteric patterns, structures that not only have potential for use as intricate, self-assembly blueprints but are also pervasive in biological systems.

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“…These mixtures have a smectic phase and a chiral nematic phase and the transition temperatures vary from 30.8 to 31.2 °C depending on the concentration of CB15. At these concentrations of chiral dopant, the cholesteric pitch ranges from 6.5 to 9.5

m [ 29 ]. Mixtures are heated and vortexed before each use.…”

Section: Methodsmentioning

confidence: 99%

Chiral Liquid Crystal Lenses Confined in Microchannels

et al. 2020

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It is known that the liquid crystalline smectic-A phase has geometric defects, called focal conic domains, which can be used as gradient-index microlenses. Cholesteric (chiral nematic) phases also have topological defects with a central symmetry and a singularity at their center. We explore a weakly chiral system in which both types of defects can be present in the same material at different temperatures, and with this strategy we create lenses whose focal length is tunable with temperature. We measure the focal length of the tunable lenses, and we investigate the behavior of the defects near the phase transition. We identify the experimental conditions that make the simultaneous presence of the smectic focal conic domains and the circular cholesteric domains possible, such as the concentration of chiral dopant and the rate of heating and cooling. The transformation of focal conic domains into circular cholesteric domains is a new example of memory at the phase transition between smectic-A and nematic liquid crystals.

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Measurement of helical twisting power based on axially symmetrical photo-aligned dye-doped liquid crystal film

Cited by 27 publications

References 13 publications

Effects of chiral dopant on electro-optical properties of nematic liquid crystal cells under in-plane switching and non-uniform vertical electric fields

Effects of chiral dopant on electro-optical properties of nematic liquid crystal cells under in-plane switching and non-uniform vertical electric fields

Change in Stripes for Cholesteric Shells via Anchoring in Moderation

Chiral Liquid Crystal Lenses Confined in Microchannels

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