Thermoassisted Photorecording in Chiral Smectic Azodye Copolymers

2001 ◽  
Vol 709 ◽  
Author(s):  
Mikhail V. Kozlovsky ◽  
Wolfgang Haase ◽  
Matthias Rehahn
Keyword(s):  
Order Parameter ◽  
Liquid Crystalline ◽  
Polarized Light ◽  
Holographic Gratings ◽  
Copolymer Films ◽  
Shock Heating ◽  
Mesophase Formation ◽  
Photoinduced Birefringence ◽  
High Diffraction Efficiency ◽  
High Diffraction

ABSTRACTIllumination of photochromic liquid-crystalline (PCLC) copolymer films with polarized light during the mesophase formation has been studied. Both thick pressed and thin spin-coated, the films show prominent increase in photoinduced orientation, as compared with conventional isothermal photorecording. Two methods of the thermoassisted recording have been suggested, one of those with simultaneous cooling of the film and another one after a shock heating and quenching. The photoinduced birefringence, Δnind, and the order parameter of photochromic groups, Sazo, have been measured. The thermally assisted recording produces holographic gratings with high diffraction efficiency, η, up to 20-30%.

scholarly journals Design and Realization of a Compact Efficient Beam Combiner, Based on Liquid Crystal Pancharatnam–Berry Phase Gratings

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 220
Author(s):  
Boxuan Gao ◽  
Jeroen Beeckman ◽  
Kristiaan Neyts
Keyword(s):  
Liquid Crystal ◽  
Berry Phase ◽  
Polarized Light ◽  
Laser Beams ◽  
Circularly Polarized Light ◽  
Circularly Polarized ◽  
Beam Combiner ◽  
High Diffraction Efficiency ◽  
High Diffraction ◽  
Crystal Mixture

We demonstrate a laser beam combiner based on four photo-patterned Pancharatnam–Berry (PB) phase gratings, which is compact and has high diffraction efficiency for incident circularly polarized light. The nematic liquid crystal mixture E7 is used as anisotropic material, and the thickness of the layer is controlled by spacers. The beam combiner can bring two parallel laser beams closer to each other while remaining parallel. This work shows the potential to realize components based on flat optical LC devices.

Design and Fabrication of Volume Holographic Gratings with Large Angular Bandwidth and High Diffraction Efficiency

2021 ◽  
Vol 41 (2) ◽  
pp. 0205001
Author(s):  
鲁婷婷 Lu Tingting ◽  
冯奇斌 Feng Qibin ◽  
王梓 Wang Zi ◽  
吕国强 Lü Guoqiang
Keyword(s):  
Diffraction Efficiency ◽  
Holographic Gratings ◽  
High Diffraction Efficiency ◽  
High Diffraction

scholarly journals Recording of high efficiency volume Bragg gratings in a photopolymer using diffraction from very weak pre-recorded gratings

2016 ◽  
Vol 2 (1) ◽  
Author(s):  
Dennis Bade ◽  
Izabela Naydenova ◽  
Vincent Toal ◽  
Suzanne Martin
Keyword(s):  
Data Storage ◽  
Diffraction Efficiency ◽  
High Efficiency ◽  
Strong Dependence ◽  
Optical Systems ◽  
Second Step ◽  
Holographic Gratings ◽  
Single Beam ◽  
High Diffraction Efficiency ◽  
High Diffraction

AbstractA two-step method of writing high diffraction efficiency holographic gratings in photopolymer using just one writing beam during the second step is discussed. The technique is based on the use of weak gratings (<1%) recorded during a first step which during the second step are illuminated with a single beam to form strong highly efficient holographic gratings. The weak grating provides a second interfering beam by diffracting a small portion of the illuminating light. Although effects such as beam pumping and twowave mixing arewell known in dynamic re-writable recording media such as photorefractives, the ability to write with one beam, or ‘pump’ gratings is not usually observed in photopolymer materials. Other methods of recording with a single beam have been reported, especially for data storage, but they use compact optical systems, polarization effects or lenticular devices to produce the required second beam. In this method, the second beam is produced within the photopolymer medium. Earlierwork by the authors reported increases in efficiency of weak photopolymer gratings illuminated by a single exposure beam, and more recently evidence was presented that diffraction at the weak pre-recorded grating was responsible for this effect. Here we demonstrate a strong dependence of the diffraction efficiency on grating thickness and show that the method allows the writing of high diffraction efficiency gratings in adverse conditions using a single beam. The possibility of angular multiplexing is also demonstrated. The technique may find application in writing information using pre-recorded weak holographic gratings and, potentially, in other data storage applications. In this paper it is shown that multiple new gratings can be writtenwhich are angularly separated and distinct from the pre-written grating and it is also possible to choose one grating from among a number of pre-written gratings and selectively amplify it without amplifying the others.

High-diffraction-efficiency holographic gratings in C_60-doped nematics

2009 ◽  
Vol 48 (33) ◽  
pp. 6506 ◽  
Author(s):  
Yong Zhang ◽  
Fengfeng Yao ◽  
Yanbo Pei ◽  
Xiudong Sun
Keyword(s):  
Diffraction Efficiency ◽  
Holographic Gratings ◽  
High Diffraction Efficiency ◽  
High Diffraction

Formation of positive and negative anisotropic holographic gratings depending on recording energy in photoreactive liquid crystalline copolymer films

2012 ◽  
Vol 107 (3) ◽  
pp. 741-748
Author(s):  
A. Emoto ◽  
A. Tashima ◽  
M. Kondo ◽  
M. Okada ◽  
S. Matsui ◽  
...  
Keyword(s):  
Liquid Crystalline ◽  
Holographic Gratings ◽  
Copolymer Films

Polarization holographic gratings with high diffraction efficiency recorded in azopolymer PAZO

2018 ◽  
Vol 50 (5) ◽  
Author(s):  
L. Nedelchev ◽  
D. Ivanov ◽  
N. Berberova ◽  
V. Strijkova ◽  
D. Nazarova
Keyword(s):  
Diffraction Efficiency ◽  
Holographic Gratings ◽  
High Diffraction Efficiency ◽  
High Diffraction

scholarly journals Study of Azo Dye-n TPEB Mixtures in the Nematic and Smectic B Phases by Means of Polarized Light Absorption

1998 ◽  
Vol 53 (10-11) ◽  
pp. 813-818
Author(s):  
Danuta Bauman ◽  
Ewa Chrzumnicka ◽  
Roman Dąbrowskia
Keyword(s):  
Phase Transition ◽  
Light Absorption ◽  
Azo Dye ◽  
Order Parameter ◽  
Nematic Phase ◽  
Liquid Crystalline ◽  
Polarized Light ◽  
Structural Form ◽  
Phase Transition Temperatures ◽  
Clearing Temperature

Abstract The influence of the dichroic azo dye on the phase transition temperatures of the mesogenic homolo-gous series of 1-[4-n-alkyl-biphenyl]-2-[4-isothio-cyanatophenyl] ethane (nTPEB) for n = 2 -10 has been examined. For the dye-nTPEB mixtures the polarized absorption spectra as a function of tem-perature have been recorded. From these spectra the order parameter of the dye dissolved in the liquid crystalline hosts in the whole region of the nematic phase has been determined. The order parameter has revealed the odd-even alternation, similarly as the clearing temperature. In the smectic B phase the mosaic texture has been observed and conclusions concerning structural form of this phase have been drawn.

Oriental behaviour of some homologues of 4-n-pentyl-phenylthio-4′-n-alkoxybenzoate doped with dichroic dye

2008 ◽  
Vol 16 (3) ◽  
Author(s):  
D. Bauman ◽  
A. Zięba ◽  
E. Mykowska
Keyword(s):  
Liquid Crystal ◽  
Order Parameter ◽  
Liquid Crystalline ◽  
Orientational Order ◽  
Polarized Light ◽  
Emission Spectra ◽  
Smectic C ◽  
Fluorescence Measurements ◽  
Dichroic Dye ◽  
Linearly Polarized

AbstractThe long-range orientational order of three members of 4-n-pentylphenylthio-4′-n-alkoxybenzoate $$ (\bar nS5) $$ series doped with a dichroic dye was studied by means of electronic absorption and fluorescence measurements. The order parameters <P2> and <P4> as well as the orientational distribution function were determined on the basis of absorption and emission spectra of linearly polarized light recorded as a function of temperature in the nematic, smectic A, and smectic C phases. An influence of the dye molecular structure on the orientational order of the dye/liquid crystal mixture was observed. Moreover, the dependence of the order parameter values on the length of the alkoxy chain in liquid crystal molecules was found. It was shown that the order parameter <P4>, obtained from fluorescence measurements, can be helpful in recognizing the second-order or weakly first-order transitions between various liquid crystalline phases.

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