Meng Chao, Li Weijian, Xie Zhonglin, Zhang Lu, Xu Lei, Gao Feng, Zhang Wending, Mei Ting, Zhao Jianlin
Opt Lett. 2021 Nov 15;46(22):5554-5557. doi: 10.1364/OL.443079.
Plasmonic tip nanofocusing has gained much attention owing to its wide application in the field of nanospectroscopy. Here, we present the Au nanosphere (AuNS)-assisted coupling ultrafast surface plasmon polaritons (SPP) background-free tip nanofocusing. The plasmonic tip was prepared by attaching an AuNS on the shaft of an Au conical tip fabricated by electrochemical etching. The AuNS was adopted as an antenna to couple the far-field excitation light to the propagating SPP along the shaft to the tip apex for achieving power compression. Importantly, we experimentally and theoretically demonstrate that such a plasmonic tip can realize background-free ultrafast SPP tip nanofocusing with radially polarized features in a wide spectral range based on the localized SPP resonance effect supported by AuNS. Furthermore, the intensity of the tip nanofocusing light field has strong polarization dependence under linearly polarized light excitation, providing a powerful platform for spatiotemporal light control on the nanoscale. Our technique realizes remote excitation of background-free tip nanofocusing with a structured light feature, and it holds promising potential for tip-enhanced nanospectroscopies, nonlinear nanophotonics, etc.
由于表面等离激元尖端纳米聚焦在纳米光谱领域的广泛应用，它已备受关注。在此，我们展示了金纳米球（AuNS）辅助耦合的超快表面等离激元极化激元（SPP）无背景尖端纳米聚焦。通过将金纳米球附着在经电化学蚀刻制造的金锥形尖端的轴上制备等离激元尖端。金纳米球被用作天线，将远场激发光沿轴耦合到传播的表面等离激元极化激元，直至尖端顶点以实现功率压缩。重要的是，我们通过实验和理论证明，基于金纳米球支持的局域表面等离激元共振效应，这种等离激元尖端能够在宽光谱范围内实现具有径向极化特征的无背景超快表面等离激元极化激元尖端纳米聚焦。此外，在线偏振光激发下，尖端纳米聚焦光场的强度具有很强的偏振依赖性，为纳米尺度上的时空光控制提供了一个强大的平台。我们的技术实现了具有结构化光特征的无背景尖端纳米聚焦的远程激发，并且在尖端增强纳米光谱学、非线性纳米光子学等方面具有广阔的应用前景。
