Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology , Rolla, Missouri 65409, United States.
Nano Lett. 2018 Jan 10;18(1):520-527. doi: 10.1021/acs.nanolett.7b04515. Epub 2017 Dec 8.
We propose a universal design scheme for a new type of chiral metamaterials based on plasmonic slanted nanoapertures simply milled in a single metal layer. Strong optical chirality is introduced by tilting nanoapertures with almost arbitrary shape along a certain direction to break all the mirror symmetries. As a typical example, chiral metamaterial based on slanted split-ring apertures is demonstrated with giant circular dichroism in transmission (CDT) over 78% at 760 nm. We reveal that the high CDT originates from the circularly dichroic mode coupling process in the slanted nanoapertures induced by spin-dependent field overlap conditions. Furthermore, tunable CDT is presented through the in-plane rotation of nanoapertures to form chiral images with controllable image contrast. Besides, chiral metamaterials with slanted nanoapertures of two other shapes including L-shaped aperture and rectangular aperture are also presented with large circular dichroism. We envision that our demonstrated chiral metamaterials enable promising platforms for a variety of applications in nonlinear optics, chiral imaging and sensing, spectroscopy, and polarization manipulation.
我们提出了一种基于等离子体倾斜纳米孔的新型手性超材料的通用设计方案，该方案只需在单个金属层中简单地铣削倾斜纳米孔。通过将具有几乎任意形状的纳米孔沿某个方向倾斜，可以打破所有的镜像对称，从而引入强光学手性。作为一个典型的例子，基于倾斜的分裂环孔的手性超材料在 760nm 处具有超过 78%的巨大透射圆二色性（CDT）。我们揭示了高 CDT 源自倾斜纳米孔中由自旋相关场重叠条件引起的圆二色模耦合过程。此外，通过纳米孔的面内旋转，可以实现可调谐的 CDT，从而形成具有可控图像对比度的手性图像。此外，还提出了具有 L 形孔和矩形孔两种其他形状的倾斜纳米孔的手性超材料，它们也具有较大的圆二色性。我们设想，我们所展示的手性超材料为非线性光学、手性成像和传感、光谱学以及偏振操控等各种应用提供了有前景的平台。
