Browsing by Author "Kadan, V. M."

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Open Access
High-quality alignment of nematic liquid crystals using periodic nanostructures created by nonlinear laser lithography
(Elsevier B.V., 2018) Pavlov, I. A.; Rybak, A. S.; Dobrovolskiy, A. M.; Kadan, V. M.; Blonskiy, I. V.; Kazantseva, Z. I.; Gvozdovskyy, I. A.
It is well known that today two main and well studied methods for alignment of liquid crystals has been used, namely: rubbing and photoalignment technologies, that lead to the change of anisotropic properties of aligning layers and long-range interaction of the liquid crystal molecules in a mesophase. In this manuscript, we use the nonlinear laser lithography technique, which was recently presented as a fast, relatively low-cost method for a large area micro and nanogrooves fabrication based on laser-induced periodic surface structuring, as a new perspective method of the alignment of nematic liquid crystals. 920 nm periodic grooves were formed on a Ti layer processed by means of the nonlinear laser lithography and studied as an aligning layer. Aligning properties of the periodic structures of Ti layers were examined by using a combined twist LC cell. In addition, the layer of the nanostructured Ti was coated with an oxidianiline-polyimide film with annealing of the polymer film followed without any further processing. The dependence of the twist angle of LC cells on a scanning speed and power of laser beam during processing of the Ti layer was studied. The azimuthal anchoring energy of Ti layers with a periodic nanostructure was calculated. The maximum azimuthal anchoring energy for the nanostructured Ti layer was about 4.6 × 10−6 J/m2, which is comparable to the photoalignment technology. It was found that after the deposition of a polyimide film on the periodic nanostructured Ti layer, the gain effect of the azimuthal anchoring energy to ~1 × 10−4 J/m2 is observed. Also, AFM study of aligning surfaces was carried out.
Open Access
Ultrashort light pulses in transparent solids: propagation peculiarities and practical applications
(National Academy of Sciences of Ukraine, 2019-08) Blonskyi, I. V.; Kadan, V. M.; Pavlova, S. V.; Pavlov, Ihor A.; Shpotyuk, O. I.; Khasanov, O. K.
The peculiarities of the femtosecond filamentation in Kerr media has been studied using a set of time-resoling experimental techniques. These include the temporal self-compression of a laser pulse in the filamentation mode, repulsive and attractive interactions of filaments, and influence of the birefringence on the filamentation. The propagation of femtosecond laser pulses at the 1550-nm wavelength in c-Si is studied for the first time using methods of time-resolved transmission microscopy. The nonlinear widening of the pulse spectrum due to the Kerr- and plasma-caused self-phase modulation is recorded.