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2026

Electronically Controlled Continuous-Phase Liquid Crystal Fresnel Zone Plate

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A team led by Stephen M. Morris and Zhiyu Xu at the University of Oxford has presented a design, fabrication, and characterization method for continuous-phase Fresnel zone plates (FZPs) embedded in polymerizable nematic liquid crystals (LCs) between glass substrates, using two-photon polymerization–based direct laser writing. Unlike conventional binary LC diffractive elements, the authors’ devices exhibit a smooth, continuous three-dimensional phase profile. They demonstrate two devices with envelope phase profiles of 2π and 4π radians, respectively. Polarized light microscopy and digital holographic microscopy confirm that the polymerized regions faithfully follow the expected spatially varying phase distribution. Far-field measurements reveal that the 2π-radian FZP produces a strongly focused spot at 0 Vpp and ceases to focus at higher voltages. In contrast, the 4π-radian FZP exhibits zoom-like behavior, switching between two focal lengths: 24 mm at 0 Vpp and 48 mm at an intermediate voltage of 2.1 Vpp; at even higher voltages, focusing completely disappears. Compared with binary Fresnel zone plates of the same size and focal length, the continuous-phase design nearly doubles the focusing efficiency and enables switchable, compact, zoom-capable, and energy-efficient optical components. This approach opens new opportunities for advanced applications such as augmented and virtual reality, adaptive optics, and other next-generation photonic systems.

The research findings were published on April 17, 2026, in Light: Science & Applications under the title “Electrically switchable continuous phase liquid crystal Fresnel zone plate.”