Lu D Y, Cao X, Wang K J, He M D, Wang D, Li J, Zhang X M, Liu L, Luo J H, Li Z, Liu J Q, Xu L, Hu W D, Chen X
Opt Express. 2018 Dec 24;26(26):34956-34964. doi: 10.1364/OE.26.034956.
We demonstrate a flat optical lens based on plasmonic reflectarray metasurface, which consists of a planar array of hyperbolic-shaped aluminum (Al) nanoantenna separated from an Al ground plane by a SiO spacer. The gradual change in the width of the Al nanoantenna enables unique broadband (400-700 nm) to focus on the visible band because of its hyperbolic reflection-phase profile. The focal length of metalens is quickly decreased with the increase of wavelength in the short wavelength region (400-550 nm), compensating the chromatic aberration in traditional lenses. In long wavelength region (550-700 nm), the focal length has only a slight change, thereby minimizing chromatic aberration. Furthermore, the proposed metalens creates a small focal spot beyond diffraction limit, while maintaining high focusing efficiency. Our method of simple and anisotropic nanoantenna is used to realize wide phase tuning range offers a novel strategy to design braodband metalens, and our metalens has widespread applications in compact camera, telescope, and microscope.
我们展示了一种基于表面等离激元反射阵列超表面的平面光学透镜，它由双曲线形铝（Al）纳米天线的平面阵列组成，该阵列通过SiO间隔层与Al接地平面隔开。由于其双曲线反射相位分布，Al纳米天线宽度的逐渐变化使得能够在可见波段实现独特的宽带（400 - 700 nm）聚焦。在短波长区域（400 - 550 nm），金属透镜的焦距随着波长的增加而迅速减小，补偿了传统透镜中的色差。在长波长区域（550 - 700 nm），焦距只有轻微变化，从而使色差最小化。此外，所提出的金属透镜在超越衍射极限的情况下产生小的焦斑，同时保持高聚焦效率。我们采用简单且各向异性的纳米天线来实现宽相位调谐范围的方法为设计宽带金属透镜提供了一种新颖策略，并且我们的金属透镜在紧凑型相机、望远镜和显微镜中具有广泛应用。
