We develop a new approach for creating photonic metasurfaces based on nematic liquid crystal material. The periodical modulation of the LC director field is imposed by nanoscale change of the alignment properties of polyimide thin layer by means of focused ion beam treatment. The resulted spatially periodic modulation with a period determined by that of the pattern at the substrate provides distinct photonic properties of LC layer. A part of transmitted light is redistributed into a few first diffraction orders. The diffraction is switchable by electric field with millisecond switching times.
Two electrooptical effects in a system consisting of subwavelength aluminum gratings and a nematic liquid crystal (LC)
layer are discussed. The aluminum gratings produced by a focused ion beam lithography act as interdigitated electrodes,
which allows application of an electric field to a very thin fraction of LC layer contacting the grating. The first of the
electrooptical effects is associated with an enhanced TE-polarized light transmission of the gratings and the surface
induced twist deformation in the bulk of the LC layer, whereas the second one is caused by an influence of the
electrically driven LC surface layer on the plasmonic resonance and the related dip of the TM-polarized grating
transmission. Besides the different polarizations, the two effects have dramatically different response times. In the case
of the plasmonic effect, the measured response time is found to be of 20 - 30 microseconds that is three orders of
magnitude faster compared to the switching based on the surface induced twist effect.