Light- and electro- induced Fredericks transition in liquid crystal cells with photosensitive chalcogenide glasses surfaces As2S3

Abstract

In this paper we represent light- and electro- induced Fredericks transition in liquid crystal cells with 5 CB on thin photosensitive chalcogenide glassy films As2S3 as command surfaces. Easy axis reorientation in a cell with nematic liquid crystals under the low intensity illumination with non-polarized beam (0.7…2mWt; 473nm) and decreasing of the Fredericks transition in dc field were observed. We suggest that easy axis reorientation with the optical illumination in the presence of a dc electric field is due to a light-induced desorption process on the photosensitive surface As2S3. We believe that the decreasing of the Fredericks transition voltage is caused by light-induced free charges in chalcogenide layer that discharge electrical double layer on the LC - chalcogenide interface. As a consequence, the energy of interaction between the liquid crystal molecules and the constant electric field near the surface overcome the anchoring energy, and, as a result, the reorientation of the director of LC in polar plane takes place in this case. From this point of view the utilization of the effects of light-induced anisotropy in inorganic materials, in particular, in chalcogenide glasses for photoalignment of LCs looks very promising.