Liquid-crystal Fresnel zone plate: Fabricated by microrubbing

A novel liquid-crystal (LC) Fresnel zone plate (FZP) is fabricated only by the LC molecular alignment process without the need for surface relief structures and patterned electrodes. It is theoretically described that the Fresnel-lens-like phase profile is achieved under optimum LC molecular orientation conditions and the polarization state of incident light, that is, the retardation of the LC cell is (n + 1/2)lambda (n is an integer) and the incident light is circularly polarized. The optical properties of the fabricated LC FZP are experimentally investigated. Good focusing properties are confirmed (the full width at half maximum of the spot is approximately 8% larger than that of the diffraction limit) and the light intensity of the focusing spot is found to be controllable by adjusting applied voltage.