Chiral systems (consisting of materials and incident radiation) respond differently to left- and right-handed circularly polarized light macroscopically. As a consequence, only chiral materials show intrinsic macroscopic optical activity, and only chiral systems generate circularly polarized light from linearly polarized incident light. In the nanoscopic regime, in contrast to this general rule for macroscopic cases, it is theoretically expected that achiral (nonchiral) systems can locally generate circularly polarized fields. Here, we report experimental evidence for that situation in achiral systems consisting of gold nanostructures and linearly polarized incident light. The local circularly polarized fields were visualized by near-field polarimetry imaging, and the spatial features of the observed circularly polarized fields were qualitatively reproduced by a simple dipole model. The present results may provide a novel technique to produce controllable circularly polarized optical fields in nanospaces.

中文翻译：

---

线性偏振光激发的非手性金属纳米结构附近光场的成像手征性

手性系统（由材料和入射辐射组成）在宏观上对左旋和右旋圆偏振光有不同的响应。结果，仅手性材料表现出固有的宏观光学活性，并且仅手性系统从线性偏振入射光产生圆偏振光。在纳米范围内，与宏观情况下的一般规则相反，从理论上讲，非手性（非手性）系统可以局部产生圆极化场。在这里，我们报告了由金纳米结构和线性偏振入射光组成的非手性系统中这种情况的实验证据。通过近场旋光成像可以观察到局部圆偏振场，通过简单的偶极子模型定性地再现了观测到的圆极化场的空间特征。本发明的结果可以提供一种在纳米空间中产生可控的圆偏振光场的新颖技术。