Kabakova I V, de Hoogh A, van der Wel R E C, Wulf M, le Feber B, Kuipers L
FOM Institute AMOLF, Science park 104, 1098 XG Amsterdam, The Netherlands.
Blackett Laboratory, Imperial College London, London SW7 2AZ, United Kingdom.
Sci Rep. 2016 Mar 7;6:22665. doi: 10.1038/srep22665.
Near-field imaging is a powerful tool to investigate the complex structure of light at the nanoscale. Recent advances in near-field imaging have indicated the possibility for the complete reconstruction of both electric and magnetic components of the evanescent field. Here we study the electro-magnetic field structure of surface plasmon polariton waves propagating along subwavelength gold nanowires by performing phase- and polarization-resolved near-field microscopy in collection mode. By applying the optical reciprocity theorem, we describe the signal collected by the probe as an overlap integral of the nanowire's evanescent field and the probe's response function. As a result, we find that the probe's sensitivity to the magnetic field is approximately equal to its sensitivity to the electric field. Through rigorous modeling of the nanowire mode as well as the aperture probe response function, we obtain a good agreement between experimentally measured signals and a numerical model. Our findings provide a better understanding of aperture-based near-field imaging of the nanoscopic plasmonic and photonic structures and are helpful for the interpretation of future near-field experiments.
近场成像是研究纳米尺度下光的复杂结构的有力工具。近场成像的最新进展表明了完全重建倏逝场的电场和磁场分量的可能性。在此，我们通过在收集模式下进行相位和偏振分辨近场显微镜，研究沿亚波长金纳米线传播的表面等离激元极化激元波的电磁场结构。通过应用光学互易定理，我们将探针收集的信号描述为纳米线倏逝场与探针响应函数的重叠积分。结果，我们发现探针对磁场的灵敏度近似等于其对电场的灵敏度。通过对纳米线模式以及孔径探针响应函数进行严格建模，我们在实验测量信号与数值模型之间获得了良好的一致性。我们的发现有助于更好地理解基于孔径的纳米级等离子体和光子结构的近场成像，并有助于解释未来的近场实验。
