Broadband dielectric metalens for polarization manipulating and superoscillation focusing of visible light
Broadband dielectric metalens for polarization manipulating and superoscillation focusing of visible light
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用于可见光偏振操纵和超振荡聚焦的宽带介电超透镜
DOI：
10.1021/acsphotonics.9b01356
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发表时间：
2019
期刊：
影响因子：
7
通讯作者：
Weiguo Chu
中科院分区：
文献类型：
--
作者：
Zhixiang Wu;Fengliang Dong;Shuo Zhang;Shaokui Yan;Gaofeng Liang;Zhihai Zhang;Zhongquan Wen;Gang Chen;Luru Dai;Weiguo Chu
超振荡光学器件在过去的几年中得到了广泛的研究。由于其独特的聚焦特性，聚焦柱面偏振波在超分辨成像和粒子操纵等方面的应用具有很大的吸引力。然而，已报道的用于柱面偏振光聚焦的超振荡透镜存在与精确的同轴对准有关的困难，这可能导致超振荡特征的严重扭曲。此外，传统的偏振转换器在可见光波段只有几十纳米的窄带宽，这限制了柱面偏振波的宽带聚焦。在这项工作中，提出了一种非晶硅介电准原子，在可见光范围内具有独立的偏振转换和二元相位调制功能。基于所提出的金属原子，提出了一种数值孔径(NA)为0.93的超振荡介质金属透镜，并对其进行了优化，以实现方位偏振光的宽带产生和超振荡聚焦。该方法首先将线偏振波转换为方位偏振波，然后聚焦成一个超振荡的方位偏振空心点。实验结果表明，在518.1-683.5 nm的波长范围内形成了内径为0.355λ-0.490λ的空斑。这种简单的方法为超分辨率应用提供了另一种产生具有超振荡特征的矢量波的途径。
Superoscillatory optical devices have been widely investigated in the past several years. Due to their unique focusing properties, the ones that focus cylindrically polarized waves are attractive for such applications as super-resolution imaging and particle manipulation. However, the superoscillatory lenses reported for the focusing of cylindrically polarized light suffer from difficulties related to precise coaxial alignment, which might lead to the substantial distortions of the superoscillatory features. Moreover, conventional polarization converters only have a narrow bandwidth of several tens of nanometers in the visible spectrum, which limits the broadband focusing of cylindrically polarized waves. In this work, an amorphous silicon dielectric meta-atom is proposed with the integrated functions of independent polarization conversion and binary phase modulation in the visible spectrum range. Based on the proposed meta-atom, a superoscillatory dielectric metalens with a high numerical aperture (NA) of 0.93 is proposed and optimized for the broadband generating and superoscillation focusing of azimuthally polarized lights. The linearly polarized wave was first converted into azimuthally polarized ones, and then focused into a superoscillation hollow spot of azimuthal polarization (AP). The experimental results demonstrate the formation of hollow spots with inner sizes of 0.355λ–0.490λ in the wavelength range of 518.1–683.5 nm. This simple approach paves an alternative pathway of generating vector waves with superoscillation features for super-resolution applications.