arXiv subjects

A. Rybak

Publications and source records attributed to A. Rybak.

3 recordsLinked to original sources

arXiv2020

Azimuthal and polar anchoring energies of aligning layers structured by nonlinear laser lithography

In spite of the fact that there are different techniques in the creation of the high-quality liquid crystals (LCs) alignment by means of various surfaces, the azimuthal and polar anchoring energies as well as the pre-tilt angle are important parameters to all of them. Here, the modified by a certain manner aligning layers, previously formed by nonlinear laser lithography (NLL), having high-quality nano-periodic grooves on Ti surfaces, recently proposed for LC alignment was studied. The change of the scanning speed of NLL in the process of nano-structured Ti surfaces and their further modification by means of ITO-coating, and deposition of polyimide film has enabled different aligning layers, whose main characteristics, namely azimuthal and polar anchoring energies, were measured. For the modified aligning layers, the dependencies of the twist and pre-tilt angles for LC cells filled by nematic E7 (Δε > 0) and MLC-6609 (Δε < 0) were obtained. Also the contact angle for droplets of isotropic liquid (glycerol), and nematic LCs was measured for the various values of the scanning speed during the laser processing.

physics.app-ph↗

arXiv2017

The alignment of nematic liquid crystal by the Ti layer processed by nonlinear laser lithography

It is well known that the alignment of liquid crystals can be realized by rubbing or photoalignment technologies. Recently nonlinear laser lithography was introduced as a fast, relatively low-cost method for large area nano-grating fabrication based on laser-induced periodic surface structuring. In this letter for the first time the usage of the nonlinear laser lithography as a perspective method of the alignment of nematics was presented. By nonlinear laser lithography, microgrooves with about 1 μm period were formed on Ti layer. The microstructured Ti layer was coated with oxidianiline-polyimide film with annealing of the polymer followed without any further processing. Aligning properties of microstructured Ti layers were examined with combined twist LC cell. The dependencies of the twist angle of LC cells and azimuthal anchoring energy of layers on scanning speed and power of laser beam during processing of the Ti layer were the focus of our studies as well. The maximum azimuthal anchoring energy, obtained for pure microstructured Ti layer, is comparable with photoalignment technology. It was found that the deposition of polyimide film on microstructured Ti layer leads to the gain effect of the azimuthal anchoring energy. Also, AFM study of aligning surfaces was carried out.

cond-mat.soft↗

arXiv2017

Transient dynamics of nonlinear magneto-optical rotation

We analyze nonlinear magneto-optical rotation (NMOR) in rubidium vapor subjected to continuously-scanned magnetic field. By varying magnetic-field sweep rate, a transition from traditionally-observed dispersive-like NMOR signals (low sweep rate) to oscillating signals (higher sweep rates) is demonstrated. The transient oscillatory behavior is studied versus light and magnetic-field parameters, revealing a strong dependence of the signals on magnetic-sweep rate and light intensity. The experimental results are supported with density-matrix calculations, which enable quantitative analysis of the effect. Fitting of the signals simulated versus different parameters with a theoretically-motivated curve reveals presence of oscillatory and static components in the signals. The components depend differently on the system parameters, which suggests their distinct nature. The investigations provide insight into dynamics of ground-state coherence generation and enable application of NMOR in detection of transient spin couplings.

physics.atom-ph↗