Polarization-independent and electrically tunable liquid-crystal fresnel lenses based on photoalignment in dye-doped liquid crystals

This work demonstrates polarization-independent and electrically tunable liquid-crystal (LC) Fresnel lenses based on photoalignment in dye-doped liquid crystals (DDLCs). The LC alignments in the adjacent odd and even zones of the LC Fresnel lens are orthogonally hybrid alignments. Those are generated by surface treatment of homeotropic and homogeneous alignment layers, and the dyeadsorption layer onto the UV-cured surface-relief Fresnel zone plate. The maximum focusing efficiency (̃34.14%) of the fabricated LC Fresnel lens by applying a suitable AC voltage is close to the maximal theoretical focusing efficiency of a binary phase LC Fresnel lens (̃40.5%). Additionally, the focusing efficiency is polarization-independent and electrically tunable.