Nanocomposites and nanomaterials 

Dielectric properties of hybrid liquid crystal cells with SiO2 and TiO2 nanoporous films
Telbiz G.1, Bugaychuk S.2, Tarakhan L.2, Glushchenko A.3, 
1 Physico-inorganic Chemistry Department, Institute of Physical Chemistry of the NAS of Ukraine. Prospect Nauki,31, Kyiv-03029, Ukraine. E-mail: gtelbiz@yahoo.com
2 Physics of Crystals Department, Institute of Physics of the NAS of Ukraine. Prospect Nauki, 46, Kyiv-03039, Ukraine.
3Physics  Department, University of Colorado at Colorado Springs, Colorado Springs, Colorado 80918, USA

Recently liquid crystals (LC) are considering as perspective materials for manipulation of waves in millimeter diapason, including filtering, frequency-phase coding and multiplexing of THz signals [1]. That is very demanded for applications in communication systems as allows one to realize the real tools for mobile communication in this diapason. The dielectric properties of LC depend strongly not only on the type of used LC and their impurities, but also on the quality of the surfaces on the substrates of the cells. But in our latest researches we show that nonlinear properties in LC cells will be improved if to use a non-smoothing surface [2]. An inhomogeneous surface promotes to generation of noncontrolable defects of the molecular orientations on this surface that makes to easier expansion of the molecular reorientation to the bulk of the LC cells under action of acting waves (e.g. laser beams). To study such properties we have prepared hybrid LC cells, which include a substrate with inhomogeneous surface, namely SiO2 or TiO2 mesoscopic films [2]. The mesoscopic films themselves  demonstrate variety of optical and luminescent properties [3], making them perspective for applications in the dynamic holography and laser generation in the optical diapason. In the present work we investigate the manipulation of the dielectric properties in such hybrid LC cells with the excitation by signals on the THz frequencies. 

 1.	Economou E., Lovejoy J., Harward I., Nobles J.E., Kula P., Herman J., Glushchenko A., Celinski Z.  Physics Review Applied.-2017.-12.-P.1-31.
 2.	Bugaychuk S., Iljin A., Telbiz G., Zhulai D., Leonenko E., Romanovska L., Gridyakina A., Bordyuh A.,Kravchuk M., Polishchuk A.  Molecular Liquids -2018.- to be published. 
 3.	A. Kazakevičius, D. Peckus, L. Valkunas,  E.Leonenko, G.Telbiz and V. Gulbinas   Journal of Phys. Chem. C, 119 (2015) 19126−19133.