Highly efficient liquid crystal based diffraction grating induced by polarization holograms at the aligning surfaces

Low-scattering and highly efficient orientational gratings are obtained, exploiting polarizationholography to modulate the in-plane anchoring axis at both surfaces of a planar nematic cell.Polarization-sensitive azo-dye-doped polyimide films are used as aligning layers. For proper valuesof cell thickness and spatial periodicity of the gratings, the director configuration in the nematic bulkis a perfect replica of the polarization gratings recorded on the aligning layers. High first-orderdiffraction efficiency, up to 98%, is observed in thin grating regime. External ac voltage allows toadjust the efficiency over the whole range for arbitrary cell thickness.