Electro-optically addressed fast dynamic gratings with near-surface photo-orientation in nematic liquid crystals
Year: 2026
Type: preprint
Abstract: Fast electro-optical switching controlled by light in nematic LC-based cells are considered. Using a two-wave mixing technique involving diffraction and selfdiffraction of light beams on induced phase dynamic grating, we observe fast flashes of light with generation of many diffracted orders at the output. Such flashes can be attributed to the absorption current due to the appearance of photoinduced unstable charge on the surface of the LC cell substrates. The strongest high-intensity flashes are indicated in half-twist cell of pure nematic LC, as well as in hybrid LC (HLC) cells containing an Au nano-island film on one of the substrates. The particularity of HLCs is that they exhibit an optically addressed response when the external voltage is turnedoff to the cell. The surface-induced photorefractive effect arising from the breaking of electroneutrality upon illuminating by a spatially inhomogeneous laser beam, in our case a periodic light interference pattern, underlies the explanation of this fast switching. Both the switching time and the diffraction efficiency depend on the surface morphology, where it specifies the mechanisms of photoinducing nonequilibrium charge. Our theoretical modeling based on the zero-flow approximation of the Ericksen-Leslie model describing the kinetics of the reorientation angle for the LC-director, supporting the formation of short-lived dynamic gratings, which agrees well with the experimental results. So is the dependence of the switching time on the system parameters, in particular, on the period of the light interference pattern.
Source: HAL
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7204018935