Metasurfaces offer a unique platform to realize flat lenses, reducing the size and complexity of imaging systems and thus enabling new imaging modalities. In this paper, we designed a bilayer helicity-dependent continuous varifocal dielectric metalens in the near-infrared range. The first layer consists of silicon nanopillars and functions as a half-wave plate, providing the helicity-dependent metasurface by combining propagation phase and geometric phase. The second layer consists of phase-change material Sb2S3 nanopillars and provides tunable propagation phases. Upon excitation with the circularly polarized waves possessing different helicities, the metalens can generate helicity-dependent longitudinal focal spots. Under the excitation of linear polarized light, the helicity-dependent dual foci are generated. The focal lengths in this metalens can be continuously tuned by the crystallization fraction of Sb2S3. The zoom range is achieved from 32.5 µm to 37.2 µm for right circularly polarized waves and from 50.5 µm to 60.9 µm for left circularly polarized waves. The simulated focusing efficiencies are above 75% and 87% for the circularly and linearly polarized waves, respectively. The proposed metalens has potential applications in miniaturized devices, including compact optical communication systems, imaging, and medical devices.
Bibliografisk noteFunding Information:
Funding. National Natural Science Foundation of China (11604167, 61875099); Natural Science Foundation of Zhe-jiang Province (LGJ18F050001, LY18F050005, LY19A040004); Natural Science Foundation of Ningbo (2018A610093, 202003N4007); Villum Fonden (00022988, 37372); The K. C. Wong Magna Fund at Ningbo University.
National Natural Science Foundation of China (11604167, 61875099); Natural Science Foundation of Zhejiang Province (LGJ18F050001, LY18F050005, LY19A040004); Natural Science Foundation of Ningbo (2018A610093, 202003N4007); Villum Fonden (00022988, 37372); The K. C. Wong Magna Fund at Ningbo University.
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