Gryb Dmytro, Wendisch Fedja J, Aigner Andreas, Gölz Thorsten, Tittl Andreas, de S Menezes Leonardo, Maier Stefan A
Chair in Hybrid Nanosystems, Nano Institute Munich, Department of Physics, Ludwig-Maximilians-Universität München, 80539 Munich, Germany.
Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, PE, Brazil.
Nano Lett. 2023 Oct 11;23(19):8891-8897. doi: 10.1021/acs.nanolett.3c02168. Epub 2023 Sep 19.
Two-dimensional chiral metasurfaces seem to contradict Lord Kelvin's geometric definition of chirality since they can be made to coincide by performing rotational operations. Nevertheless, most planar chiral metasurface designs often use complex meta-atom shapes to create flat versions of three-dimensional helices, although the visual appearance does not improve their chiroptical response but complicates their optimization and fabrication due to the resulting large parameter space. Here we present one of the geometrically simplest two-dimensional chiral metasurface platforms consisting of achiral dielectric rods arranged in a square lattice. Chirality is created by rotating the individual meta-atoms, making their arrangement chiral and leading to chiroptical responses that are stronger or comparable to more complex designs. We show that resonances depending on the arrangement are robust against geometric variations and behave similarly in experiments and simulations. Finally, we explain the origin of chirality and behavior of our platform by simple considerations of the geometric asymmetry and gap size.
二维手性超表面似乎与开尔文勋爵对手性的几何定义相矛盾，因为通过执行旋转操作可以使它们重合。然而，大多数平面手性超表面设计通常使用复杂的超原子形状来创建三维螺旋的平面版本，尽管视觉外观并不能改善它们的旋光响应，反而由于产生的大参数空间而使它们的优化和制造变得复杂。在这里，我们展示了一种几何上最简单的二维手性超表面平台，它由排列在正方形晶格中的非手性介电棒组成。通过旋转单个超原子来产生手性，使它们的排列具有手性，并导致比更复杂设计更强或相当的旋光响应。我们表明，取决于排列的共振对几何变化具有鲁棒性，并且在实验和模拟中的表现相似。最后，我们通过对几何不对称性和间隙大小的简单考虑来解释我们平台的手性起源和行为。
