Journal
FRONTIERS IN MATERIALS
Volume 8, Issue -, Pages -Publisher
FRONTIERS MEDIA SA
DOI: 10.3389/fmats.2021.806725
Keywords
metasurface; chirality; ultra-thin; polarization conversion; transmission; high efficiency; microwave; optical superoscillation
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Funding
- National Natural Science Foundation of China [62171165, 61771172]
- Open Project of Guangxi Key Laboratory of Wireless Wideband Communication and Signal Processing
- Natural Science Foundation of Heilongjiang Province [YQ2020F002]
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This paper proposes an ultra-thin metasurface-based superoscillatory lens that can generate a sub-diffraction optical needle with a long focal depth. The lens has the advantages of simple fabrication, high efficiency, and low-profile design.
The metasurface-based superoscillatory lens has been demonstrated to be effective in finely tailoring the wavefront of light to generate focal spots beyond the diffraction limit in the far-field that is capable of improving the resolution of the imaging system. In this paper, an ultra-thin (0.055 lambda(0)) metasurface-based superoscillatory lens (SOL) that can generate a sub-diffraction optical needle with a long focal depth is proposed, which is constructed by ultra-thin chiral unit cells containing two metal split-ring resonators (SRR) with a 90 degrees twisted angle difference cladded on both sides of a 1.5 mm-thick dielectric substrate, with a high linear cross-polarized transmission coefficient around 0.9 and full phase control capability at 11 GHz. Full-wave simulation shows that SOL generates a sub-diffraction optical needle within 10.5-11.5 GHz. At the center frequency, the focal depth is 281 mm (10.3 lambda(0)) within 105-386 mm, the full width at half maximum (FWHM) is 18.5 mm (0.68 lambda(0)), about 0.7 times the diffraction limit, generally consistent with the theoretical result. The proposed ultra-thin chiral metasurface-based SOL holds great potential in integrating into practical imaging applications for its simple fabrication, high efficiency, and low-profile advantages.
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