Frequency-dependent electro-optics of liquid crystal devices utilizing nematics and weakly conducting polymers

2018 ◽  
Vol 7 (4) ◽  
pp. 243-248 ◽  
Author(s):  
Yuriy Garbovskiy ◽  
Anatoliy Glushchenko
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Conducting Polymers ◽  
Nematic Liquid Crystals ◽  
Elementary Model ◽  
Frequency Dependent ◽  
Electric Circuits ◽  
Liquid Crystal Devices ◽  
Weakly Conducting ◽  
Crystal Cells

Abstract Conducting polymer films acting as both electrodes and alignment layers are very promising for the development of flexible and wearable tunable liquid crystal devices. The majority of existing publications report on the electro-optical properties of polymer-dispersed liquid crystals and twisted nematic liquid crystals sandwiched between highly conducting polymers. In contrary, in this paper, electro-optics of nematic liquid crystals placed between rubbed weakly conducting polymers is studied. The combination of weakly conducting polymers and nematics enables a frequency-dependent tuning of the effective threshold voltage of the studied liquid crystal cells. This unusual electro-optics of liquid crystal cells utilizing nematics and weakly conducting polymers can be understood by considering equivalent electric circuits and material parameters of the cell. An elementary model of the observed electro-optical phenomenon is also presented.

scholarly journals Spontaneous helielectric nematic liquid crystals: Electric analog to helimagnets

2021 ◽  
Vol 118 (42) ◽  
pp. e2111101118
Author(s):  
Xiuhu Zhao ◽  
Junchen Zhou ◽  
Jinxing Li ◽  
Junichi Kougo ◽  
Zhe Wan ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Nonlinear Optical ◽  
Room Temperature ◽  
Nematic Liquid Crystals ◽  
Polar Liquid ◽  
Experimental Proof ◽  
Liquid Crystal Devices ◽  
Optical Responses ◽  
Electric Analog

Recently, a type of ferroelectric nematic fluid has been discovered in liquid crystals in which the molecular polar nature at molecule level is amplified to macroscopic scales through a ferroelectric packing of rod-shaped molecules. Here, we report on the experimental proof of a polar chiral liquid matter state, dubbed helielectric nematic, stabilized by the local polar ordering coupled to the chiral helicity. This helielectric structure carries the polar vector rotating helically, analogous to the magnetic counterpart of helimagnet. The helielectric state can be retained down to room temperature and demonstrates gigantic dielectric and nonlinear optical responses. This matter state opens a new chapter for developing the diverse polar liquid crystal devices.

Photo-Induced Surface Alignment Of Nematic Liquid Crystals On Polyamide-Imide Layers

1995 ◽  
Vol 413 ◽  
Author(s):  
David C. Rich ◽  
Enid K. Sichel ◽  
Peggy Cebet
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Ultraviolet Radiation ◽  
Short Wavelength ◽  
Optical Transmission ◽  
Nematic Liquid Crystals ◽  
Uv Exposure ◽  
Surface Alignment ◽  
Linearly Polarized ◽  
Crystal Cells

ABSTRACTA technique for producing surface-induced liquid crystal nematic alignment is presented. The alignment film is a simple, inexpensive polyamide-imide, which is treated with linearly polarized short wavelength ultraviolet radiation (λ = 254 nm). The alignment performance of UV-aligned layers is shown by optical transmission of the liquid crystal cells to be comparable to that of brushed layers. Strong alignment is produced within minutes of UV exposure and is maintained with long exposures.

scholarly journals Electro-Optical Switching of Dual-Frequency Nematic Liquid Crystals: Regimes of Thin and Thick Cells

Crystals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 314 ◽  
Author(s):  
Olha Melnyk ◽  
Yuriy Garbovskiy ◽  
Dario Bueno-Baques ◽  
Anatoliy Glushchenko
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Optical Switching ◽  
Nematic Liquid Crystals ◽  
Optical Response ◽  
Thin Layers ◽  
Optical Performance ◽  
Dual Frequency ◽  
Crystal Cells ◽  
Cell Thickness

Conventional display applications of liquid crystals utilize thin layers of mesogenic materials, typically less than 10 µm. However, emerging non-display applications will require thicker, i.e., greater than 100 µm, layers of liquid crystals. Although electro-optical performance of relatively thin liquid crystal cells is well-documented, little is known about the properties of thicker liquid crystal layers. In this paper, the electro-optical response of dual-frequency nematic liquid crystals is studied using a broad range (2–200 µm) of the cell thickness. Two regimes of electro-optical switching of dual-frequency nematics are observed and analyzed.

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 Liquid Crystal Devices for Beam Steering Applications

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 247
Author(s):  
Rowan Morris ◽  
Cliff Jones ◽  
Mamatha Nagaraj
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Adaptive Optics ◽  
Beam Steering ◽  
Optical Components ◽  
Advantages And Disadvantages ◽  
Liquid Crystal Devices

Liquid crystals are valuable materials for applications in beam steering devices. In this paper, an overview of the use of liquid crystals in the field of adaptive optics specifically for beam steering and lensing devices is presented. The paper introduces the properties of liquid crystals that have made them useful in this field followed by a more detailed discussion of specific liquid crystal devices that act as switchable optical components of refractive and diffractive types. The relative advantages and disadvantages of the different devices and techniques are summarised.

Optically isotropic liquid crystal media formulated by doping star-shaped cyclic oligosiloxane liquid crystal surfactants in twin nematic liquid crystals

Soft Matter ◽  
2015 ◽  
Vol 11 (19) ◽  
pp. 3772-3779 ◽  
Author(s):  
Namil Kim ◽  
Dae-Yoon Kim ◽  
Minwook Park ◽  
Yu-Jin Choi ◽  
Soeun Kim ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Nematic Liquid Crystals ◽  
Isotropic Liquid

The formation of an optically isotropic liquid crystal (LC) medium by doping the star-shaped LC molecular surfactant in a nematic LC medium may allow us to develop new electro-optical LC devices.

scholarly journals Electrically Controlled Diffraction Grating in Azo Dye-Doped Liquid Crystals

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1051 ◽  
Author(s):  
Chuen-Lin Tien ◽  
Rong-Ji Lin ◽  
Chi-Chung Kang ◽  
Bing-Yau Huang ◽  
Chie-Tong Kuo ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Electric Fields ◽  
Azo Dye ◽  
Nematic Liquid Crystals ◽  
Polarized Light ◽  
Dielectric Anisotropy ◽  
Linear Effect ◽  
Periodic Distribution ◽  
The Difference

This research applies the non-linear effect of azo dye-doped liquid crystal materials to develop a small, simple, and adjustable beam-splitting component with grating-like electrodes. Due to the dielectric anisotropy and optical birefringence of nematic liquid crystals, the director of the liquid crystal molecules can be reoriented by applying external electric fields, causing a periodic distribution of refractive indices and resulting in a diffraction phenomenon when a linearly polarized light is introduced. The study also discusses the difference in the refractive index (Δn), the concentration of azo dye, and the rising constant depending on the diffraction signals. The experimental results show that first-order diffraction efficiency can reach ~18% with 0.5 wt % azo dye (DR-1) doped in the nematic liquid crystals.

scholarly journals A comparative study of nematic liquid crystals doped with harvested and non-harvested ferroelectric nanoparticles: phase transitions and dielectric properties

RSC Advances ◽  
2017 ◽  
Vol 7 (56) ◽  
pp. 35438-35444 ◽  
Author(s):  
Y. Lin ◽  
A. Daoudi ◽  
F. Dubois ◽  
J.-F. Blach ◽  
J.-F. Henninot ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Dielectric Properties ◽  
Comparative Study ◽  
Dielectric Spectroscopy ◽  
Nematic Liquid Crystals ◽  
Broadband Dielectric Spectroscopy

Broadband dielectric spectroscopy is used to determine the dielectric properties and phase transitions of the 4-n-octyl-4′-cyanobiphenyl liquid crystal (8CB) doped with harvested and non-harvested ferroelectric nanoparticles.

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