A simple method to make a switchable liquid crystal (LC) Fresnel lens with high diffraction efficiency and a low driving voltage was proposed based on the photo-induced surface modification of the vertical alignment layer. UV illumination alters the pretilt angle of alignment layers, a Fresnel zone-distribution hybrid alignment in the homeotropic LC cell can be straightforwardly achieved through UV exposure, yielding a concentric structure of the Fresnel phase LC lens. A remarkable diffraction efficiency of ~31.4%, close to the measured diffraction efficiency of the used Fresnel-zone-plate mask of 32%, was detected using a linearly polarized incident beam.

A switchable liquid crystal (LC) Fresnel lens was demonstrated by the UV-modified alignment layer for producing an alternation of hybrid-aligned and vertically-aligned LC zones. A polarizationindependent Fresnel lens can be obtained by circular rubbing, and a high diffraction efficiency of ~23% is reached with a low driving voltage of 1.2 V.

The nanoparticles-induced vertical alignment (NIVA) of the nematic liquid crystals (LC) was proposed to make a tunable liquid-crystal flat microlens with hybrid-aligned nematic (HAN) mode, which was fabricated using micro drop technology. The minute amount of nanoparticle solution was dropped on the selective area, which was surrounded by homogeneous alignment layer. Due to vertical alignment induced by the nanoparticles, the liquid-crystal concave microlens with concentric non-uniform distribution of the refractive index was then formed in the planar LC cell. The divergence effect of this flat lens was observed and its focal length can be electrically controlled at applied voltages.