Flexoelectric response of a liquid crystal layer with a temperature-induced orientational transition

1997 ◽  
Vol 23 (5) ◽  
pp. 341-342 ◽  
Author(s):  
M. V. Khazimullin ◽  
A. P. Krekhov ◽  
Yu. A. Lebedev ◽  
O. A. Scaldin
Keyword(s):  
Liquid Crystal ◽  
Crystal Layer ◽  
Liquid Crystal Layer ◽  
Orientational Transition

scholarly journals Optofluidic Platform Based on Liquid Crystals in X-Cut Lithium Niobate: Thresholdless All-Optical Response

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 908
Author(s):  
Fabrizio Ciciulla ◽  
Annamaria Zaltron ◽  
Riccardo Zamboni ◽  
Cinzia Sada ◽  
Francesco Simoni ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Light Intensity ◽  
Lithium Niobate ◽  
Photovoltaic Effect ◽  
Optical Control ◽  
Crystal Layer ◽  
Liquid Crystal Layer ◽  
Threshold Behaviour ◽  
All Optical

In this study, we present a new configuration of the recently reported optofluidic platform exploiting liquid crystals reorientation in lithium niobate channels. In order to avoid the threshold behaviour observed in the optical control of the device, we propose microchannels realized in a x-cut crystal closed by a z-cut crystal on the top. In this way, the light-induced photovoltaic field is not uniform inside the liquid crystal layer and therefore the conditions for a thresholdless reorientation are realized. We performed simulations of the photovoltaic effect based on the well assessed model for Lithium Niobate, showing that not uniform orientation and value of the field should be expected inside the microchannel. In agreement with the re-orientational properties of nematic liquid crystals, experimental data confirm the expected thresholdless behaviour. The observed liquid crystal response exhibits two different regimes and the response time shows an unusual dependence on light intensity, both features indicating the presence of additional photo-induced fields appearing above a light intensity of 107 W/m2.

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)’.

Anchoring Induced by Porous Substrate on a Liquid Crystal Layer

1994 ◽  
Vol 239 (1) ◽  
pp. 257-261 ◽  
Author(s):  
Francesco Simoni ◽  
Ferdinando Basile ◽  
Francesco Bloisi ◽  
Luciano Vicari ◽  
Fouad Aliev
Keyword(s):  
Liquid Crystal ◽  
Crystal Layer ◽  
Porous Substrate ◽  
Liquid Crystal Layer

Numerical modelling of twisted nematic devices

1983 ◽  
Vol 309 (1507) ◽  
pp. 203-216 ◽  
Keyword(s):  
Liquid Crystal ◽  
Electric Fields ◽  
Low Cost ◽  
Three Dimensional ◽  
Physical Parameters ◽  
Crystal Layer ◽  
Liquid Crystal Layer ◽  
Chiral Nematic ◽  
Twisted Nematic ◽  
Three Dimensional Simulations

Over most of each active region in nematic and chiral nematic twist cells the motion and configuration of the liquid crystal layer does not vary appreciably with position parallel to the surfaces. In such laminar regions the statics, dynamics and optics ot the cell can be accurately simulated at low cost on a computer of moderate size, given the appropriate physical parameters. Methods and recent advances in simulation of laminar regions are reviewed. Bistable twist cells are simulated for illustration. Important problems of stability and edge effects in the presence of electric fields await solution with two- or three-dimensional simulations.

scholarly journals A compact fluorescence polarization analyzer with high-transmittance liquid crystal layer

2018 ◽  
Vol 89 (2) ◽  
pp. 024103 ◽  
Author(s):  
Osamu Wakao ◽  
Ken Satou ◽  
Ayano Nakamura ◽  
Ken Sumiyoshi ◽  
Masanori Shirokawa ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Fluorescence Polarization ◽  
Crystal Layer ◽  
Liquid Crystal Layer ◽  
Polarization Analyzer

Optical Performance of Photonic Crystal Filter with Liquid Crystal Layer

2010 ◽  
Vol 37 (11) ◽  
pp. 2834-2837 ◽  
Author(s):  
宋立涛 Song Litao ◽  
何杰 He Jie ◽  
王华磊 Wang Hualei ◽  
韩毅昂 Han Yiang ◽  
李涛 Li Tao
Keyword(s):  
Liquid Crystal ◽  
Photonic Crystal ◽  
Crystal Layer ◽  
Optical Performance ◽  
Liquid Crystal Layer

Surface-Induced Flexoelectric Domains in Asymmetrically Strong-Weak Anchored MBBA Films

1982 ◽  
Vol 37 (4) ◽  
pp. 334-341
Author(s):  
H. P. Hinov
Keyword(s):  
Liquid Crystal ◽  
Electric Field ◽  
Dielectric Anisotropy ◽  
Crystal Layer ◽  
Liquid Crystal Layer ◽  
Surface Anchoring ◽  
Threshold Voltages ◽  
Domain Period ◽  
Cell Thickness

Abstract The longitudinal surface-induced flexoelectric domains, previously obtained in symmetrically weak-anchored nematic layers have been further investigated in asymmetrically strong-weak anchored MBBA layers. The threshold voltages indicating the onset of the flexoelectric instabilities are high for thin cells (d = 9 μm, Uth = 10 V) and small for thick cells (d = 150 μm, Uth =1.5 V). Pronounced minima in the curves p vs. d and Uth vs. d, where p is the domain period and d is the cell thickness, were obtained. The flexoelectric domains were replaced by electrohydrodynamic instabilities only in the case of strong azimuthal anchoring of the liquid crystal layer.The role of the sign and the value of the dielectric anisotropy, the homogeneity of the electric field as well as the asymmetry in the surface anchoring are discussed in detail.

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