Hidden photoalignment of liquid crystals in the isotropic phase

Ouskova, E.; Fedorenko, D.; Reznikov, Yuriy; Shiyanovskii, Sergij V.; Su, Linli; West, John L.; Kuksenok, O. V.; Francescangeli, O.; Simoni, F.

doi:10.1103/physreve.63.021701

Cited by 70 publications

(56 citation statements)

References 11 publications

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“…In fact the efficiency of adsorption or desorption is strongly dependent on incident light polarization. 4,5 In particular in our experimental arrangement, the pump light was polarised parallel to the initial cell orientation, which favours light absorption by MR molecules followed by desorption from the irradiated surface and subsequent adsorption from the bulk. On the contrary, if the incident light is polarised orthogonal to the initial easy axis, as in Fig.…”

Section: à áKmentioning

confidence: 99%

“…These include enhancement of nonlinear optical response, 1,2 light-induced phototransformations, 2 photo-alignment techniques, [3][4][5][6] optical memory effects, 7,8 and optical processing methods. 9 A system widely studied is the mixture of the nematic pentyl-cyanobiphenil and the azo-dye Methyl Red (5CB þ MR) in weight concentration typically between 0.1 and 1%.…”

Section: Introductionmentioning

confidence: 99%

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Light-controlled electric Freedericksz threshold in dye doped liquid crystals

Lucchetti

Catàni

Simoni

2014

Journal of Applied Physics

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We report the results of measurements of the threshold of Freedericksz transition in a nematic liquid crystal doped by Methyl-red. We show that in case of dc field the threshold voltage can decrease or increase depending on the light dose, due to the light-induced desorption and adsorption of charge complexes from and on the irradiated surface, that has been recently demonstrated. This effect has the potential to be exploited in optical devices such as liquid crystal microlenses and spatial light modulators.

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Section: à áKmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Light-controlled electric Freedericksz threshold in dye doped liquid crystals

Lucchetti

Catàni

Simoni

2014

Journal of Applied Physics

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“…The authors also suggested that the absorption dichroism of LC molecules caused the anisotropic desorption of these molecules from the surface, making the adsorbed layer anisotropic with the long molecular axis perpendicular to the direction of polarization. Ouskova et al [40,41] showed that photoalignment of LCs in an MR-doped LC system depends strongly on the intensity of the pumping beam. They attributed the photoalignment effect to two mechanisms-adsorption and desorption, which dominate in strong-and weak-intensity regimes, respectively.…”

Section: Bulk-mediated Photo-isomerization and Adsorption Effectsmentioning

confidence: 99%

Photo-Alignment Technology

Lin

2014

Topics in Applied Physics

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LCDs are used in many everyday devices, including mobile phones, notebook computers and wide screen televisions. A typical LCD is composed of two glass substrates between which is a gap that is filled with LC. The arrangement of the LC is controlled by the boundary condition of an alignment film. A long-range orientational interaction causes the preferable alignment of a LC by the surface boundary to extend into the LC bulk. The alignment layer is typically rubbed with a special cloth to induce a unidirectional alignment of the LC. In the first devices based on twisted LCs, these LCs were aligned only by rubbing transparent electrodes. The rubbing technique became much more reliable when the glass substrate was covered with a rubbed polymer layer. The rubbing of polymers is a very simple technique and it is now extensively utilized in both small scientific laboratories and large LCD factories.Despite the extensive use of rubbing in LCD manufacturing, it has some serious shortcomings that arise from the contact involved in rubbing. These critically affect the production of the most recent generation of LCDs and miniature LC photonic devices. First, rotational rubbing for the polymer surface causes the accumulation of static charges and the formation of fine dust particles. The accumulation of static electricity may destroy the transistors or diodes in the LCD. The second shortcoming is the effect of decreasing in manufacturing yield. Rubbing for large and high-resolution active matrix LCDs (AMLCDs) involve additional difficulties that are associated with the precise control of the rubbing characteristics. Other problems are the difficulty of producing local structures with the required LC director alignment in the selected areas of the device. Finally, this method cannot be used to align LCs in closed volumes.For all of the above reasons, new alignment solutions and approaches are sought. There are some alternative methods of rubbing include laser writing, micro-rubbing, ion beam irradiation and photoalignment. Of these methods, the

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“…When the dye contains the azo-group, the photoinduced reversible conformational transformations are very promising for reversible optical memories or photochemical switching operations. There are also many studies which investigate the phenomena occurring in such systems [8][9][10][11][12][13]. Most of these studies are focused on molecular reorientation produced by electrical or optical fields.…”

Section: Introductionmentioning

confidence: 99%