Electrically variable diffraction in spherulitic liquid crystals

Haas, W.; Adams, James E.

doi:10.1063/1.1655464

Cited by 49 publications

(22 citation statements)

References 9 publications

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“…3(a) and 3(b)), whereas, at the far zone, they are a manifestation of the spatial periodicity of the bubbles. 18,25 At the far zone, the diffraction pattern is composed of a series of welldefined bright spots that represented the Fourier transform of the bubble distribution in the plane of the cell. Figures 4(a) and 4(b) show the experimental and calculated diffraction patterns of the bubble structure of Fig.…”

Section: Resultsmentioning

confidence: 99%

“…These bubbles can arrange themselves in hexagonal arrays. Such formation of bubble arrays was observed for the first time in 1974, simultaneously by both Kawachi et al 17 and Haas et al 18 in liquid crystal materials with negative dielectric anisotropy. Both groups noted that CLCN bubbles were generated by applying a DC or AC electric pulse strong enough and with a suitable frequency to induce electrohydro-dynamical effects.…”

Section: Introductionmentioning

confidence: 88%

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Liquid crystal bubbles forming a tunable micro-lenses array

Hamdi

Petriashvili

Lombardo

et al. 2011

Journal of Applied Physics

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Cholesteric liquid crystals with long pitch confined in homeotropic cells can be used to generate stable but distorted and localized liquid crystal structures exhibiting spherulitic textures, known as “bubbles.” As these bubbles can be induced by an external electric field with a narrow range following the confinement ratio C=d/p ≈1 (d representing cell thickness and p representing cholesteric pitch), it is possible to obtain electrically controlled micro-lenses. Here we investigated the optical and electro-optical properties of such liquid crystal bubbles for creating an array of micro-lenses with electrically tunable focal length.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 88%

Liquid crystal bubbles forming a tunable micro-lenses array

Hamdi

Petriashvili

Lombardo

et al. 2011

Journal of Applied Physics

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“…We have found that some of the studied laser-generated structures can also be obtained spontaneously when cooling the samples from the isotropic phase (although less reliably and without the control of spatial locations) and after applying low-frequency (10 Hz) electric fields to induce hydrodynamic instability. These localized structures, along with torons and hopfions, are several members of the large family of so-called cholesteric bubbles that were typically studied when occurring spontaneously, but not well understood in past experimental works [20,[34][35][36][37][38][39][40][41][42][43][44]. We note that the study of axially symmetric cholesteric configurations reported here is not exhaustive.…”

Section: Nested Axially Symmetric Structures Of Multiple Torons Anmentioning

confidence: 86%

Two-dimensional skyrmions and other solitonic structures in confinement-frustrated chiral nematics

et al. 2014

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We explore spatially localized solitonic configurations of a director field, generated using optical realignment and laser-induced heating, in frustrated chiral nematic liquid crystals confined between substrates with perpendicular surface anchoring. We demonstrate that, in addition to recently studied torons and Hopf-fibration solitonic structures (hopfions), one can generate a host of other axially symmetric stable and metastable director field configurations where local twist is matched to the surface boundary conditions through introduction of point defects and loops of singular and nonsingular disclinations. The experimentally demonstrated structures include the so-called "baby-skyrmions" in the form of double twist cylinders oriented perpendicular to the confining substrates where their double twist field configuration is matched to the perpendicular boundary conditions by loops of twist disclinations. We also generate complex textures with arbitrarily large skyrmion numbers. A simple back-of-the-envelope theoretical analysis based on free energy considerations and the nonpolar nature of chiral nematics provides insights into the long-term stability and diversity of these inter-related solitonic field configurations, including different types of torons, cholestric-finger loops, two-dimensional skyrmions, and more complex structures comprised of torons, hopfions, and various disclination loops that are experimentally observed in a confinement-frustrated chiral nematic system.

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“…Such developments can be viewed as spatially controlled versions of randomly distributed defect structures generated by uniform quasistatic electric fi elds as shown in Refs. [ 8,9 ] four decades ago, see also Ref. [ 10,11 ] for more recent works.…”

Section: Doi: 101002/adma201400811mentioning

confidence: 98%