Photo-Alignment Effect in Liquid-Crystal Films Containing Nanoparticles and Azo-Dye

2010 ◽  
Vol 428-429 ◽  
pp. 276-279 ◽  
Author(s):  
Tsung Hsien Lin ◽  
Wen Zheng Chen
Keyword(s):  
Liquid Crystal ◽  
Azo Dye ◽  
Polyhedral Oligomeric Silsesquioxanes ◽  
Alignment Effect ◽  
Practical Applications ◽  
Liquid Crystal Films ◽  
Crystal Film ◽  
Crystal Films ◽  
Alignment Technique ◽  
Photo Alignment

This work reports the photo-alignment effect in a liquid-crystal film doped with nanoparticles and azo-dye. Vertical alignment induced by the nanoparticles polyhedral oligomeric silsesquioxanes (POSS) can be switched to homogeneous alignment by the absorption of photo-excited azo-dye. Both electro-optical and surface properties are analyzed to verify this effect. Using this photo-alignment technique in nanoparticle- and azo-dye-doped liquid crystal, the phase grating is also demonstrated. The diffraction efficiency is related to the polarization of the probe light and can be controlled by applying voltage. Both nanoparticle- and azo-dye-induced vertical and homogeneous alignments are non-contact aligning methods. Thus, the technique based on dopant-induced alignment has potential for practical applications.

Self-phase modulation in azo-dye-doped liquid crystal films

2010 ◽  
Author(s):  
Andy Ying-Guey Fuh ◽  
Chia-Wei Chu ◽  
Hui-Chi Lin ◽  
Hung-Chang Jau ◽  
Ming-Shian Li
Keyword(s):  
Liquid Crystal ◽  
Phase Modulation ◽  
Azo Dye ◽  
Self Phase Modulation ◽  
Liquid Crystal Films ◽  
Crystal Films

Polarization-independent holographic gratings based on azo-dye-doped polymer-dispersed liquid-crystal films

2010 ◽  
Vol 49 (2) ◽  
pp. 275 ◽  
Author(s):  
Andy Ying-Guey Fuh ◽  
Che-Chang Chen ◽  
Ko-Ting Cheng ◽  
Cheng-Kai Liu ◽  
Wei-Ko Chen
Keyword(s):  
Liquid Crystal ◽  
Azo Dye ◽  
Holographic Gratings ◽  
Liquid Crystal Films ◽  
Polymer Dispersed Liquid Crystal ◽  
Crystal Films ◽  
Polymer Dispersed ◽  
Doped Polymer ◽  
Polarization Independent

Calculation and Prediction: An Effective Security Device Consisted of Photo Alignment Nematic Liquid Crystal Films and Polarizers

2010 ◽  
Vol 428-429 ◽  
pp. 301-304 ◽  
Author(s):  
Ji Wei Zhou ◽  
Guang Ming Ke ◽  
Bin Wang ◽  
Wei Dong Liu ◽  
Rui Xing Li
Keyword(s):  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Polarized Light ◽  
Viewing Angle ◽  
Liquid Crystal Films ◽  
Reflected Light ◽  
Crystal Films ◽  
Photo Alignment ◽  
Security Device ◽  
Theoretical Results

The paper reports the methods for making a novel optical device consisted of photo alignment nematic liquid crystal films and polarizers. The color shift of the device depends on not only the viewing angle but also the viewing orientation. The retardation and intensity of the reflected light are theoretically calculated on the basis of Jones Matrix, and a spectral-RGB transition program is introduced to display colorful results directly. The theoretical results show excellent agreement with experimental data. It is an effective method for predicting interference color and optimizing key parameters of the device. The device can be used to protect valuable documents against fraud because of its special optical variable effects which is caused by interference of polarized light.

scholarly journals Biphotonic-induced reorientation inversion in azo-dye-doped liquid crystal films

2011 ◽  
Vol 19 (14) ◽  
pp. 13118 ◽  
Author(s):  
Hui-Chi Lin ◽  
Chia-Wei Chu ◽  
Ming-Shian Li ◽  
Andy Ying-Guey Fuh
Keyword(s):  
Liquid Crystal ◽  
Azo Dye ◽  
Liquid Crystal Films ◽  
Crystal Films

scholarly journals Electrically Tunable Fresnel Lens in Twisted-Nematic Liquid Crystals Fabricated by a Sagnac Interferometer

Polymers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1448 ◽  
Author(s):  
Bing-Yau Huang ◽  
Tsung-Hsien Lin ◽  
Tian-Yi Jhuang ◽  
Chie-Tong Kuo
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Azo Dye ◽  
Focal Length ◽  
Fresnel Lens ◽  
Sagnac Interferometer ◽  
Alignment Effect ◽  
Twisted Nematic ◽  
Linearly Polarized ◽  
Photo Alignment

This paper presents an electrically tunable Fresnel lens in a twisted nematic liquid crystal cell fabricated by using a Sagnac interferometer. When the Fresnel-patterned green beam, formed by the Sagnac interferometer, is irradiated on the azo-dye doped liquid crystal mixture, the azo-dye molecules undergo trans–cis photoisomerization and then generate the photo-alignment effect in the bright (odd) zones. The director of the liquid crystal molecules in the odd zones reorients the direction perpendicular to the polarization direction of the linearly polarized green beam. The various structures of liquid crystals in the odd and even zones will result in a phase difference and thus, a Fresnel lens can be generated. The experimental results show that the proposed Fresnel lens has a high diffraction efficiency of 31.5% under an applied alternating-currents (AC) voltage. The focal length of the Fresnel lens can also be tuned by thermally erasing the photo-alignment effect of the azo dyes and rewriting by a different Fresnel-like pattern.

Attractive mode force microscopy of chiral liquid crystal surfaces

1992 ◽  
Vol 50 (1) ◽  
pp. 268-269
Author(s):  
B.D. Terris ◽  
R. J. Twieg ◽  
C. Nguyen ◽  
G. Sigaud ◽  
H. T. Nguyen
Keyword(s):  
Liquid Crystal ◽  
Crystal Surfaces ◽  
Free Surfaces ◽  
Control Range ◽  
Force Microscopy ◽  
Liquid Crystal Films ◽  
Chiral Liquid Crystal ◽  
Crystal Films ◽  
Electrostatic Charging ◽  
And Shifts

We have used a force microscope in the attractive, or noncontact, mode to image a variety of surfaces. In this mode, the microscope tip is oscillated near its resonant frequency and shifts in this frequency due to changes in the surface-tip force gradient are detected. We have used this technique in a variety of applications to polymers, including electrostatic charging, phase separation of ionomer surfaces, and crazing of glassy films.Most recently, we have applied the force microscope to imaging the free surfaces of chiral liquid crystal films. The compounds used (Table 1) have been chosen for their polymorphic variety of fluid mesophases, all of which exist within the temperature control range of our force microscope.

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