We experimentally study the effect of rotational disorder at the unit-cell level on the optical response of chiral bilayer plasmonic metasurfaces consisting of asymmetric dimers of gold nanoantennas. The structures are fabricated based on a two-step electron-beam lithography process in combination with a precision alignment procedure. For a comprehensive characterization of the chiral optical response of the fabricated bilayer metasurfaces, we combine two different measurement strategies, namely, direct measurement of the circular transmission using circularly polarized incident light and measurement of the Jones matrix using interferometric spectroscopy with linearly polarized incident light. This allows us both to do a comprehensive analysis of the polarization dependent properties and to retrieve the effective polarization eigenstates of the metasurface in the ordered and disordered regime directly from experimental data. Our results demonstrate that rotational disorder provides a route toward chiral plasmonic metasurfaces with orthogonal, purely circular eigenstates, leading to circular dichroism and optical activity without linear birefringence. Our experimental findings are additionally complemented and verified by numerical simulations for the ordered case.

中文翻译：

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双层等离子超颖表面中的无序使能纯手性。

我们实验研究了在单位细胞水平上旋转紊乱对由金纳米天线的不对称二聚体组成的手性双层等离子体超表面的光学响应的​​影响。该结构是基于两步电子束光刻工艺与精密对准程序相结合而制成的。为了全面表征所制造的双层超表面的手性光学响应，我们结合了两种不同的测量策略，即使用圆偏振入射光直接测量圆形透射率和使用线偏振入射光通过干涉光谱法测量琼斯矩阵。这使我们既可以对偏振相关的属性进行全面分析，又可以直接从实验数据中检索有序和无序状态下的超颖表面的有效偏振本征态。我们的结果表明，旋转紊乱提供了一条通向具有正交，纯圆形本征态的手性等离子体超表面的途径，从而导致了圆二色性和光学活性，而没有线性双折射。我们的实验结果通过有序案例的数值模拟得到了补充和验证。导致圆二色性和光学活性，而没有线性双折射。我们的实验结果通过有序案例的数值模拟得到了补充和验证。导致圆二色性和光学活性，而没有线性双折射。我们的实验结果通过有序案例的数值模拟得到了补充和验证。