Zu Shuai, Sun Quan, Cao En, Oshikiri Tomoya, Misawa Hiroaki
Research Institute for Electronic Science, Hokkaido University, Sapporo 001-0021, Japan.
Center for Emergent Functional Matter Science, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan.
Nano Lett. 2021 Jun 9;21(11):4780-4786. doi: 10.1021/acs.nanolett.1c01322. Epub 2021 May 28.
The spatiotemporal origin of plasmonic chiroptical responses in nanostructures remains unexplored and unclear. Here, two orthogonally oriented Au nanorods as a prototype were investigated, with a giant chiroptical response caused by antisymmetric and symmetric mode excitations for obliquely incident left-handed circular polarization (LCP) and right-handed circular polarization (RCP) light. Time-resolved photoemission electron microscopy (PEEM) was employed to measure the near-field spatial distributions, spectra, and spatiotemporal dynamics of plasmonic modes associated with the chiroptical responses at the nanofemto scale, verifying the characteristic near-field distributions at the resonant wavelengths of the two modes and a very large spectral dichroism for LCP and RCP. More importantly, eigenmode excitations and their contributions to the ultrafast plasmonic chiroptical response in the space-time domain were directly revealed, promoting a full understanding of the ultrafast chiral origin in complex nanostructures. These findings open a way to design chiroptical nanophotonic devices for spatiotemporal control of chiral light-matter interactions.
纳米结构中等离激元手性光学响应的时空起源仍未得到探索且尚不清楚。在此，以两个正交取向的金纳米棒作为原型进行了研究，对于斜入射的左旋圆偏振（LCP）光和右旋圆偏振（RCP）光，由反对称和对称模式激发引起了巨大的手性光学响应。采用时间分辨光发射电子显微镜（PEEM）来测量与纳米飞秒尺度下的手性光学响应相关的等离激元模式的近场空间分布、光谱及时空动力学，验证了两种模式共振波长处的特征近场分布以及LCP和RCP的非常大的光谱二向色性。更重要的是，直接揭示了本征模式激发及其在时空域中对超快等离激元手性光学响应的贡献，有助于全面理解复杂纳米结构中的超快手性起源。这些发现为设计用于时空控制手性光 - 物质相互作用的手性光学纳米光子器件开辟了一条道路。
