Dependence of the molecular reorientation on the direction of incident light in azo-dye doped liquid crystals

2006 ◽  
Author(s):  
Luogen Deng ◽  
Guohui Wang ◽  
Junliang Zhang ◽  
Liyuan Luo ◽  
Bin Shao ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Azo Dye ◽  
Incident Light ◽  
Molecular Reorientation

scholarly journals Patterned Photoalignment in Thin Films: Physics and Applications

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 84
Author(s):  
Vladimir Chigrinov ◽  
Aleksey Kudreyko ◽  
Qi Guo
Keyword(s):  
Liquid Crystals ◽  
Azo Dye ◽  
Rotational Diffusion ◽  
Incident Light ◽  
Polarized Light ◽  
Photonic Devices ◽  
Dye Molecules ◽  
Ferroelectric Liquid Crystals ◽  
Dependent Change ◽  
Alignment Process

Photoalignment of liquid crystals by using azo dye molecules is a commonly proposed alternative to traditional rubbing alignment methods. Photoalignment mechanism can be well described in terms of rotational diffusion of azo dye molecules exposed by ultraviolet polarized light. A specific feature of the irradiated light is the intensity dependent change of azimuthal anchoring of liquid crystals. While there are various mechanisms of azo dye photoalignment, photo-reorientation occurs when dye molecules orient themselves perpendicular to the polarization of incident light. In this review, we describe both recent achievements in applications of photoaligned liquid crystal cells and its simulation. A variety of display and photonic devices with azo dye aligned nematic and ferroelectric liquid crystals are presented: q-plates, optically rewritable flexible e-paper (monochromatic and color), and Dammann gratings. Some theoretical aspects of the alignment process and display simulation are also considered.

scholarly journals A Planar Fresnel Lens in Reflection Type Based on Azo-Dye-Doped Cholesteric Liquid Crystals Fabricated by Photo-Alignment

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2972
Author(s):  
Bing-Yau Huang ◽  
Ting-Hui Chen ◽  
Tzu-Yeh Chen ◽  
Jia-De Lin ◽  
Tsung-Hsien Lin ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Azo Dye ◽  
Focal Length ◽  
Incident Light ◽  
Polarization State ◽  
Fresnel Lens ◽  
Dye Molecules ◽  
Cholesteric Liquid Crystals ◽  
Crystal Film ◽  
Photo Alignment

This paper presents a focusing efficiency and focal length tunable planar Fresnel lens in reflection type based on azo-dye-doped cholesterol liquid crystal film. The Fresnel-like pattern of a pumping beam can be formed by a Sagnac interferometer. When the azo-dye molecules are irradiated by the pumping beam, the photoalignment effect will be induced in the bright (odd) zones due to the trans–cis photoisomerization of azo-dye molecules. Thus, the structures of cholesteric liquid crystals in the odd zones will reorient from the imperfectly planar textures to the perfectly planar textures. The different structures of cholesteric liquid crystals in two adjacent zones will give rise to phase difference for the reflected light and thus function as a Fresnel lens. The focusing efficiency of the proposed Fresnel lens can be controlled by the applied voltages and affected by the polarization state of incident light. Moreover, various focal lengths of the Fresnel lens can be achieved by rewriting a different center radius of the Fresnel-like pattern.

Real-time holography in azo-dye-doped liquid crystals

1992 ◽  
Vol 17 (6) ◽  
pp. 441 ◽  
Author(s):  
Alan G. Chen ◽  
David J. Brady
Keyword(s):  
Liquid Crystals ◽  
Real Time ◽  
Azo Dye

Effect of Photo-Isomerization of Azo Dyes on the Photonic Bandgap in Chiral Nematics

2011 ◽  
Vol 181-182 ◽  
pp. 257-260
Author(s):  
David Statman ◽  
Andrew Jockers ◽  
Daniel Brennan
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Azo Dyes ◽  
Azo Dye ◽  
Photonic Bandgap ◽  
Methyl Red ◽  
Central Wavelength ◽  
Chiral Nematic ◽  
Anchoring Energy ◽  
Pitch Length

Chiral nematic liquid crystals prepared with Grandjean texture demonstrate a photonic bandgap whose central wavelength is proportional to the pitch length, P, of the liquid crystal and whose width is given by (ne – no)P. We show that methyl red doped chiral nematics undergo a shift in the photonic bandgap upon photo-isomerization. This shift is a result of (1) photo-induced change in anchoring energy on the nematic surface, and (2) change in the natural pitch length from the photo-isomerization of the azo dye.

Photo-alignment of liquid crystals in micro capillaries with point-by-point irradiation

2014 ◽  
Vol 22 (3) ◽  
Author(s):  
A. Siarkowska ◽  
M. Jóźwik ◽  
S. Ertman ◽  
T. Woliński ◽  
V. Chigrinov
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Azo Dye ◽  
Laser Light ◽  
Alignment Method ◽  
Uv Laser ◽  
Orientation Control ◽  
Photo Alignment

AbstractA photo-alignment method for micro capillaries based on the SD-1 azo-dye is demonstrated. In this work a liquid-crystal molecules aligning layer is created by point-by-point irradiation of the azo-dye film by using an UV laser light. The method opens up new possibilities for an improved molecules’ orientation control in both glass- and polymer-based photonic liquid crystal fibres.

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.

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