Abstract
Liquid crystals are excellent candidates for tunable optical elements due to their large birefringence and continuous tunability by external fields. A dual-frequency liquid crystal lens integrated with Pancharatnam–Berry phase was fabricated via a dynamic photo-patterning technique. The proposed lens exhibited distinctive polarization-dependent characteristics and ultra-high efficiency rates of up to 95%. Via merely alternating the frequency of the applied electric field, the switching time between unfocused and focused states was measured in submilliseconds. This work supplies a new strategy for fast-response, high-efficiency and helicity-dependent lens with merits of easy fabrication and low power consumption.
Highlights
Nowadays, liquid crystals (LCs) have experienced rapid development due to their pronounced optical anisotropy and continuous external field tunability and have become prospective candidates for tunable diffractive optical elements
dual-frequency LCs (DFLCs) polarization lensproposed via a dynamic photo-patterning technique. and
Be realized The by alternating the between incident focused/defocused states and focused/unfocused states can be realized by alternating the incident polarization and the frequency of certain applied electric field, respectively
Summary
Liquid crystals (LCs) have experienced rapid development due to their pronounced optical anisotropy and continuous external field tunability and have become prospective candidates for tunable diffractive optical elements. Several practical LC techniques, such as zone-patterned structures [4], hole or hybrid-patterned electrodes [5,6,7,8,9], and inhomogeneous polymer networks [10], have been proposed for lens fabrication. The applications of these electrically-tunable LC lenses are determined by two key parameters, switching time and optical efficiency. By introducing orthogonal azimuthal angle control of LCs, realized by a photoalignment technique, Fresnel lenses, with their diffraction efficiencies improved to 40.5%, are presented [14]. If one can supply a Crystals 2019, 9, 111; doi:10.3390/cryst9020111 www.mdpi.com/journal/crystals
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