Plasmonic nanofocusing spectral interferometry
Plasmonic nanofocusing spectral interferometry
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DOI：
10.1515/nanoph-2019-0397
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发表时间：
2020-02
期刊：
影响因子：
7.5
通讯作者：
M. Esmann;A. Chimeh;Anke Korte;J. Zhong;S. Stephan;J. Witt;G. Wittstock;N. Talebi;C. Lienau
中科院分区：
文献类型：
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作者：
M. Esmann;A. Chimeh;Anke Korte;J. Zhong;S. Stephan;J. Witt;G. Wittstock;N. Talebi;C. Lienau
摘要我们描述并展示了一种新的实验方法来测量宽带，幅度和相位分辨散射光谱的单个纳米粒子与10 nm的空间分辨率。表面等离子体激元（SPP）的纳米聚焦传播沿着轴的锥形金锥被用来创建一个空间隔离，光谱宽的纳米级光源在其最顶点。这些入射的SPP和SPP之间的干扰，从顶点反向传播导致形成一个固有的相位稳定的干涉图，我们检测到在远场部分散射SPP小康的锥形轴上的一个小突起。我们表明，这些干涉图允许重建的振幅和相位的局部光学近场周围的单个纳米粒子光耦合到锥形顶点。我们提取局部光散射光谱的颗粒和量化线加宽和光谱位移引起的尖端样品耦合。我们的实验结果支持相应的时域有限差分和耦合偶极模拟，并表明，在弱尖样品耦合的限制，测量直接探测等离子体系统的光学状态的投影局部密度。高度稳定的内联干涉仪与通过纳米聚焦的固有光学背景抑制的组合使其成为耦合混合纳米系统的光谱和时间光学响应的局部分辨研究的有前途的工具。
Abstract We describe and demonstrate a novel experimental approach to measure broadband, amplitude- and phase-resolved scattering spectra of single nanoparticles with 10-nm spatial resolution. Nanofocusing of surface plasmon polaritons (SPPs) propagating along the shaft of a conical gold taper is used to create a spatially isolated, spectrally broad nanoscale light source at its very apex. The interference between these incident SPPs and SPPs that are backpropagating from the apex leads to the formation of an inherently phase-stable interferogram, which we detect in the far field by partially scattering SPPs off a small protrusion on the taper shaft. We show that these interferograms allow the reconstruction of both the amplitude and phase of the local optical near fields around individual nanoparticles optically coupled to the taper apex. We extract local light scattering spectra of particles and quantify line broadenings and spectral shifts induced by tip-sample coupling. Our experimental findings are supported by corresponding finite-difference time-domain and coupled dipole simulations and show that, in the limit of weak tip-sample coupling, the measurements directly probe the projected local density of optical states of the plasmonic system. The combination of a highly stable inline interferometer with the inherent optical background suppression through nanofocusing makes it a promising tool for the locally resolved study of the spectral and temporal optical response of coupled hybrid nanosystems.