Photorefractive Effect in Nematic Liquid Crystal Cell with Sandwiched Structure

2001 ◽  
Vol 709 ◽  
Author(s):  
Hyun-Wuk Kim ◽  
Jong-Duk Kim
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Nematic Liquid Crystal ◽  
Capillary Flow ◽  
Photorefractive Effect ◽  
Isotropic Phase ◽  
Optical Responses ◽  
Molecular Ordering ◽  
Photorefractive Effects ◽  
Sandwiched Structure

ABSTRACTOptical responses and orientational photorefractivities of nematic liquid crystal cells doped with fullerene were investigated with a sandwiched structure. The photorefractive effect was attributed to the reorientation and switching of liquid crystals using a photoalignment layer for vertical alignment. When nematic liquid crystals were injected at a nematic phase, a better cell texture could be obtained due to the capillary flow-induced orientation effect. Samples with this method showed the higher photorefractive effects than those injected at an isotropic phase. Therefore, the state of molecular ordering is important for the orientational photorefractive effects.

New structure induced by elastic anisotropy in cylindrical nematic liquid crystal

2017 ◽  
Vol 13 (2) ◽  
pp. 4705-4717
Author(s):  
Zhang Qian ◽  
Zhou Xuan ◽  
Zhang Zhidong
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Nematic Liquid Crystal ◽  
Elastic Anisotropy ◽  
Nematic Liquid Crystals ◽  
Gennes Theory

Basing on Landau–de Gennes theory, this study investigated the chiral configurations of nematic liquid crystals confined to cylindrical capillaries with homeotropic anchoring on the cylinder walls. When the elastic anisotropy (L2/L1) is large enough, a new structure results from the convergence of two opposite escape directions of the heterochiral twist and escape radial (TER) configurations. The new defect presents when L2/L1≥7 and disappears when L2/L1<7. The new structure possesses a heterochiral hyperbolic defect at the center and two homochiral radial defects on both sides. The two radial defects show different chiralities.

scholarly journals Dissipative structures induced by photoisomerization in a dye-doped nematic liquid crystal layer

2018 ◽  
Vol 376 (2135) ◽  
pp. 20170382 ◽  
Author(s):  
I. Andrade-Silva ◽  
U. Bortolozzo ◽  
C. Castillo-Pinto ◽  
M. G. Clerc ◽  
G. González-Cortés ◽  
...  
Keyword(s):  
Phase Transition ◽  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Dissipative Structures ◽  
Input Power ◽  
Isotropic Phase ◽  
Crystal Layer ◽  
Liquid Crystal Layer ◽  
Nematic Liquid Crystal Layer ◽  
Interface Propagation

Order–disorder phase transitions driven by temperature or light in soft matter materials exhibit complex dissipative structures. Here, we investigate the spatio-temporal phenomena induced by light in a dye-doped nematic liquid crystal layer. Experimentally, for planar anchoring of the nematic layer and high enough input power, photoisomerization processes induce a nematic–isotropic phase transition mediated by interface propagation between the two phases. In the case of a twisted nematic layer and for intermediate input power, the light induces a spatially modulated phase, which exhibits stripe patterns. The pattern originates as an instability mediated by interface propagation between the modulated and the homogeneous nematic states. Theoretically, the phase transition, emergence of stripe patterns and front dynamics are described on the basis of a proposed model for the dopant concentration coupled with the nematic order parameter. Numerical simulations show quite a fair agreement with the experimental observations. This article is part of the theme issue ‘Dissipative structures in matter out of equilibrium: from chemistry, photonics and biology (part 2)’.

scholarly journals Capillary Flows of Nematic Liquid Crystal

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1029
Author(s):  
Dina V. Shmeliova ◽  
Sergey V. Pasechnik ◽  
Semen S. Kharlamov ◽  
Alexandre V. Zakharov ◽  
Eugeny P. Pozhidaev ◽  
...  
Keyword(s):  
Contact Angle ◽  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Electric Fields ◽  
Capillary Flow ◽  
Capillary Rise ◽  
Vertical Plane ◽  
Treatment Technique ◽  
Photo Alignment ◽  
Wetting Process

In this paper we report the new experimental results on the rise of a liquid crystal in flat capillaries with inner photosensitive surfaces. The capillaries with different surface orientations were prepared by the use of the photo-alignment technique. Such a surface treatment makes it possible to eliminate the noncontrollable influence of a nanorelief on the wetting process, which takes place in the rubbing treatment technique previously used in similar experiments. The dynamics of the capillary rise of a nematic liquid crystal 5CB (4-cyano-4′-pentylbiphenyl) in vertical plane capillaries with photo-aligned substrates were studied for the first time. It was found that the stationary value of a contact angle weakly depends on the direction of a planar surface orientation relative to the direction of a capillary rise. It has been shown that the application of strong electric fields resulted in a decreasing of the contact angle. The results, obtained for the nematic liquid crystal, are compared with the results of an investigation of the capillary flow in a shock-free ferroelectric smectic phase.

scholarly journals Regularity Criterion for the 3D Nematic Liquid Crystal Flows

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Jishan Fan ◽  
Tohru Ozawa
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Nematic Liquid Crystal ◽  
Regularity Criterion ◽  
Hydrodynamic Theory ◽  
Nematic Liquid Crystal Flows

We study the hydrodynamic theory of liquid crystals. We prove a logarithmically improved regularity criterion for two simplified Ericksen-Leslie systems.

Viscosity coefficients in the isotropic phase of a nematic liquid crystal

1977 ◽  
Vol 38 (2) ◽  
pp. 159-162 ◽  
Author(s):  
P. Martinoty ◽  
F. Kiry ◽  
S. Nagai ◽  
S. Candau ◽  
F. Debeauvais
Keyword(s):  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Isotropic Phase ◽  
Viscosity Coefficients

scholarly journals Stable and Metastable Patterns in Chromonic Nematic Liquid Crystal Droplets Forced with Static and Dynamic Magnetic Fields

Crystals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 138 ◽  
Author(s):  
Jordi Ignés-Mullol ◽  
Marc Mora ◽  
Berta Martínez-Prat ◽  
Ignasi Vélez-Cerón ◽  
R. Santiago Herrera ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Boundary Conditions ◽  
Isotropic Phase ◽  
Director Field ◽  
Line Defects ◽  
The One ◽  
Bulk Structures ◽  
Microscopy Images

Spherical confinement of nematic liquid crystals leads to the formation of equilibrium director field configurations that include point and line defects. Driving these materials with flows or dynamic fields often results in the formation of alternative metastable states. In this article, we study the effect of magnetic field alignment, both under static and dynamic conditions, of nematic gems (nematic droplets in coexistence with the isotropic phase) and emulsified nematic droplets of a lyotropic chromonic liquid crystal. We use a custom polarizing optical microscopy assembly that incorporates a permanent magnet whose strength and orientation can be dynamically changed. By comparing simulated optical patterns with microscopy images, we measure an equilibrium twisted bipolar pattern within nematic gems that is only marginally different from the one reported for emulsified droplets. Both systems evolve to concentric configurations upon application of a static magnetic field, but behave very differently when the field is rotated. While the concentric texture within the emulsified droplets is preserved and only displays asynchronous oscillations for high rotating speeds, the nematic gems transform into a metastable untwisted bipolar configuration that is memorized by the system when the field is removed. Our results demonstrate the importance of boundary conditions in determining the dynamic behavior of confined liquid crystals even for configurations that share similar equilibrium bulk structures.

Induction of orientational order in the isotropic phase of a nematic liquid crystal

2001 ◽  
Vol 64 (2) ◽  
Author(s):  
M. Simões ◽  
P. R. Fernandes ◽  
A. J. Palangana ◽  
S. M. Domiciano
Keyword(s):  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Orientational Order ◽  
Isotropic Phase

The breathers in nematic liquid crystals under applied electric field

2019 ◽  
Vol 33 (26) ◽  
pp. 1950319
Author(s):  
Yan Li ◽  
Xiaobo Lu ◽  
Chunfeng Hou
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Electric Field ◽  
Nematic Liquid Crystal ◽  
Dynamic Equation ◽  
Applied Electric Field ◽  
Deflection Angle ◽  
Breather Solution ◽  
The Relationship ◽  
Sg Equation

In this paper, we study the twist of the nematic liquid crystal molecules under the applied electric field. The dynamic equation of the twisted molecules is derived. It is proved to be a kind of sine-Gordon (SG) equation. We obtain the breather solution of the equation and confirm that the deflection angles of the twisted molecules can distribute in the form of breathers. We give the relationship between the molecular deflection angle and the breather frequency, and discuss the effect of electric field on breather shape and breather frequency.

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