Imaging of surface plasmon polariton fields excited at a nanometer-scale slit
Imaging of surface plasmon polariton fields excited at a nanometer-scale slit
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DOI：
10.1103/physrevb.84.245442
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发表时间：
2011-12
影响因子：
3.7
通讯作者：
L.-X. Zhang;A. Kubo;Leiming Wang;H. Petek;T. Seideman
中科院分区：
文献类型：
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作者：
L.-X. Zhang;A. Kubo;Leiming Wang;H. Petek;T. Seideman
非线性双光子光电发射电子显微镜用于对由倾斜入射激光脉冲 (~10 fs) 在银薄膜中制造的单缝处激发的表面等离子体激元 (SPP) 波包进行成像。我们对由外部激励脉冲和 SPP 波包场相干叠加形成的前向传播偏振光栅进行成像。通过系统地改变耦合狭缝宽度从亚波长到多波长尺度，我们观察到光栅强度的调制增加，这在现象学上可以通过对从入射波到SPP波的前向耦合效率的不同贡献来解释。实验的全波矢量时域有限差分 (FDTD) 模拟与实验观察结果非常吻合，并解释了其起源。特别是，FDTD 模拟说明了在倾斜入射的超快激光脉冲的激发下，偏振光栅的详细空间变化作为狭缝几何形状的函数。
Nonlinear two-photon photoemission electron microscopy is used to image surface plasmon polariton (SPP) wave packets excited by an obliquely incident laser pulse (~10 fs) at a single slit fabricated in a thin silver film. We image the forward propagating polarization grating formed by the coherent superposition of the external excitation pulse and the SPP wave packet fields. By systematically varying the coupling slit width from sub- to multiple-wavelength scale, we observe a modulated increase of the grating intensity, which is phenomenologically accounted for by distinct contributions to the forward coupling efficiency from the incident to the SPP waves. Full-wave, vectorial finite-difference time-domain (FDTD) simulation of the experiments is in good agreement with the experimental observations and explains their origin. In particular, the FDTD simulation illustrates detailed spatial variation of the polarization grating as a function of the geometry of the slit under excitation by ultrafast laser pulses at an oblique incidence.