Diffusion model of photoaligning in azo-dye layers

Abstract

The model of the rotational diffusion of the azo-dye molecules under the action of polarized uv light was used to explain the formation of the photoinduced order in azo-dye layers. We consider both the approximations of negligible and strong molecular interaction during the process of the reorientation under the field of a polarized light. We constructed an experimental setup, based on a photoelastic modulator, that allows accurate in situ measurements of the phase retardation ␦ of thin film as a function of the exposure time t exp and exposure power W ͑W/cm 2 ͒. A good agreement with experiment was observed. Fitting the experimental curves ␦͑t exp ͒ for different power values W, we can estimate the coefficient of rotational diffusion D, azo-dye order parameter S͑t exp ͒, and other parameters of the rotational diffusion model.

Effect of Azo Dyes Molecules Dimerization on Properties of LC – Dye Systems Under Laser Irradiation

“…К наиболее перспективным методам полу-чения ориентированных ЖК относится их ориен-тирование в системах ЖК-краситель с помощью светового или лазерного излучения [2][3][4][5][6][7][8][9][10][11][12][13]. Этот эффект называется фотоориентацией.…”

Generating, Separating and Polarizing Terahertz Vortex Beams via Liquid Crystals with Gradient-Rotation Directors

“…Here, a polarization-sensitive medium sulfonic azo dye SD1 (Dai-Nippon Ink and Chemicals, Tokyo, Japan) is used as the photoalignment agent. SD1 molecules tend to reorient their absorption oscillators perpendicular to the polarization direction when illuminated by a linearly polarized UV and then consequently guide the LC orientations [39].…”

Reorientation Dynamics of Chromophores in Photosensitive Polymers by Means of Coarse‐Grained Modeling

“…The reorientation of the trans isomers is driven by the conservative reorientation force derived from the empiric potential introduced in Refs. [23] and [24].T he justification for both the liability of such an approach in general, andf or the form of this potential in particularisp rovided in Section 6.…”

“…On the coarse-grainedl evel, there exists stochastic Monte Carlo approaches to the isomerization transitionf or the description of polarization gratings as well as surfacer elief gratings. [16,17] Therefore, in our previous analytical [18][19][20] and computer simulation studies, [21,22] we simplified ad escription of the light-induced anisotropy by applying an effective orientation potential to the trans isomerst hat reorients the chromophores perpendicular to the vector E.T his potentialh ave been introduced independently by Chigrinove ta l. [23] and by Saphiannikovae t al. [24] The influence of the cis isomers was assumed to be negligible under visible-light irradiation, owing to their smallf raction (less than 10 %).…”