Disclosing dark mode of femtosecond plasmon with photoemission electron microscopy
Disclosing dark mode of femtosecond plasmon with photoemission electron microscopy
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DOI：
10.1088/1361-6463/aa83a0
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发表时间：
2017-09
期刊：
影响因子：
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通讯作者：
B. Ji;Qian Wang;Xiao-wei Song;H. Tao;Yinping Dou;Xun Gao;Z. Hao;Jingquan Lin
中科院分区：
文献类型：
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作者：
B. Ji;Qian Wang;Xiao-wei Song;H. Tao;Yinping Dou;Xun Gao;Z. Hao;Jingquan Lin
金属纳米环的等离子体暗模式在传感和表面增强拉曼光谱（SERS）等领域具有广阔的应用前景。迄今为止，对纳米环中等离子体暗模式的研究大多是远场光谱或近场模拟。本文利用光电发射电子显微镜（PEEM）对单个金纳米环上飞秒暗模等离子体的近场分布进行了非侵入成像。实验结果表明，在飞秒光的不同偏振方向和波长下，PEEM图像中的强电子发射分布与时域有限差分模拟计算的四重等离子体模式的模式在定性上一致。同时，发现观测到的PEEM图像与模拟的光电子发射图之间存在热点分布的差异，这可能是由于纳米材料费米能级附近的能带结构和飞秒激光脉冲的时间分布等因素造成的。等离子体暗模式的实空间近场成像提供了对近场的基本理解，并为进一步推进暗模式在传感和SERS等领域的应用铺平了道路。
The plasmonics dark mode of metal nanorings has potential in the field of e.g. sensing and surface-enhanced Raman spectroscopy (SERS). Most of the investigations on the plasmonics dark mode in a nanoring have been on far-field spectroscopy or near field simulations so far. In this paper, the near-field distribution of the femtosecond dark mode plasmon on an individual gold nanoring is mapped non-invasively using photoemission electron microscopy (PEEM). The experimental results show that strong electron emission distributions in the PEEM images under different polarization directions and wavelengths of femtosecond light are in qualitative agreement with the pattern of quadruple plasmon mode calculated using finite-difference time-domain simulation. In the meantime, it is found that there is a discrepancy in hot spot distribution between the observed PEEM image and the simulated photoelectron emission pattern, which is attributed to some possible factors, such as band structure near the Fermi level of the nanoring material and the temporal profile of femtosecond laser pulse. Real-space near-field imaging of the plasmonics dark mode provides a fundamental understanding of the near field and paves the way for further advancing the applications of dark mode in the field of e.g. sensing and SERS.