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arXiv · 1709.00573

Silicon nitride metalenses for unpolarized high-NA visible imaging

Zhi-Bin Fan·Zeng-Kai Shao·Ming-Yuan Xie·Xiao-Ning Pang·Wen-Sheng Ruan·Fu-Li Zhao·Yu-Jie Chen·Si-Yuan Yu·Jian-Wen Dong
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Abstract

As one of nanoscale planar structures, metasurface has shown excellent superiorities on manipulating light intensity, phase and/or polarization with specially designed nanoposts pattern. It allows to miniature a bulky optical lens into the chip-size metalens with wavelength-order thickness, playing an unprecedented role in visible imaging systems (e.g. ultrawide-angle lens and telephoto). However, a CMOS-compatible metalens has yet to be achieved in the visible region due to the limitation on material properties such as transmission and compatibility. Here, we experimentally demonstrate a divergent metalens based on silicon nitride platform with large numerical aperture (NA~0.98) and high transmission (~0.8) for unpolarized visible light, fabricated by a 695-nm-thick hexagonal silicon nitride array with a minimum space of 42 nm between adjacent nanoposts. Nearly diffraction-limit virtual focus spots are achieved within the visible region. Such metalens enables to shrink objects into a micro-scale size field of view as small as a single-mode fiber core. Furthermore, a macroscopic metalens with 1-cm-diameter is also realized including over half billion nanoposts, showing a potential application of wide viewing-angle functionality. Thanks to the high-transmission and CMOS-compatibility of silicon nitride, our findings may open a new door for the miniaturization of optical lenses in the fields of optical fibers, microendoscopes, smart phones, aerial cameras, beam shaping, and other integrated on-chip devices.

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Zhi-Bin Fan, Zeng-Kai Shao, Ming-Yuan Xie, Xiao-Ning Pang, Wen-Sheng Ruan, Fu-Li Zhao, Yu-Jie Chen, Si-Yuan Yu, Jian-Wen Dong. 2017-09-02. Silicon nitride metalenses for unpolarized high-NA visible imaging. https://doi.org/10.1103/physrevapplied.10.014005

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