Nanocomposites and nanomaterials

Modeling of surface-induced photorefractive mechanism in nematic liquid crystal cells
Mystetskyi V.A., Bugaychuk S.A.
Department of Physics of Crystals, Institute of Physics of the NAS of Ukraine. Prospect Nauki, 46, Kyiv-03039, Ukraine. 
E-mail: misteckiyviktor@ukr.net

Modern photonics of nanomaterials is aimed at the development of new elements of optoelectronics, which are characterized by a high response rate   under the influence of electric or light fields. Holographic methods of transmission, processing and conversion of optical images, which are used in various fields, including communication technologies, space research, study of biological objects, medicine, are rapidly developing. The main element of such systems are spatial light modulators (SLM), which are created on the basis of liquid crystals (LCs).  The main mechanism is the reorientation of LCs molecules, but the response time of molecules to the electrical signal is quite large - usually more than 100 ms. It is important to create LC systems with ultra-fast response time.
We have proposed and studied composite LC cells containing nano-island gold films [1]. We have developed a mathematical model of the surface-induced photorefractive effect (SIPE) in the composite cells for the case of a two-wave mixing. The model includes a number of processes that operate simultaneously in the ITO-LC interface under the action of spatially modulated light and applied voltage. The dynamics of non-equilibrium charge formation in the interface is considered, as a result of which the spatial-periodic distribution of the electric field is formed. The dynamic Erickson-Leslie model of spatial reorientation of the LC director [2] is used under the action of the created nonequilibrium electric field at the interface, which leads to spatial modulation of the refractive index, i.e. the recording of a dynamic grating. Computer experiments were performed on the basis of the Comsol package. The work has great prospects for practical application because it shows the direction of technology for creating dynamic electro-optical elements based on liquid crystas with ultra-fast switching time (less than 10 μs).

1.	 Bugaychuk S, Viduta L., Gridyakina A., Bordyuh H., Styopkin V., L. Tarakhan, V. Nechytaylo, Faster nonlinear optical response in liquid crystal cells containing gold nano-island films // Appl.Nanosci. -2020.-10:-P. 4965.
2.	Blinov L.M. Structure and Properties of Liquid Crystals. -2011.- Springer.