Far-field midinfrared superresolution imaging and spectroscopy of single high aspect ratio gold nanowires
Far-field midinfrared superresolution imaging and spectroscopy of single high aspect ratio gold nanowires
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DOI：
10.1073/pnas.1916433117
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发表时间：
2020-02-04
影响因子：
11.1
通讯作者：
Kuno, Masaru
中科院分区：
文献类型：
--
作者：
Aleshire, Kyle;Pavlovetc, Ilia M.;Kuno, Masaru
对中红外区的单个纳米结构进行成像和记录光谱的方法有限。在这里，我们使用红外光热外差成像(IR-PHI)来探测单一的、高深宽比的Au纳米线(NWS)。在2,800到4,000厘米(-1)范围内记录的2.5-3.9微米长的原子核的光谱显示了由于原子核的法布里-珀罗模式引起的一系列共振。重要的是，IR-PHI图像显示的结构反映了NW吸收的空间分布，并允许将共振指定为m=3和m=4的法布里-珀罗模式。这种远场光学测量已被用于成像金属纳米结构中的等离子体共振的模式结构，并通过IR-PHI的超分辨率能力而成为可能。NW谱的线宽范围从35到75 meV，在一些情况下，显著低于由大块Au Drude衰减参数预测的极限值。这些线宽意味着较长的退相时间，并归因于NWS中辐射衰减和电阻加热效应的减少。与以前使用电子显微镜或近场光学扫描技术对NW法布里-珀罗模式进行成像研究相比，IR-PHI实验是在环境条件下进行的，从而能够详细研究环境如何影响中红外等离子体。
Limited approaches exist for imaging and recording spectra of individual nanostructures in the midinfrared region. Here we use infrared photothermal heterodyne imaging (IR-PHI) to interrogate single, high aspect ratio Au nanowires (NWs). Spectra recorded between 2,800 and 4,000 cm(-1) for 2.5-3.9-mu m-long NWs reveal a series of resonances due to the Fabry-Perot modes of the NWs. Crucially, IR-PHI images show structure that reflects the spatial distribution of the NW absorption, and allow the resonances to be assigned to the m = 3 and m = 4 Fabry-Perot modes. This farfield optical measurement has been used to image the mode structure of plasmon resonances in metal nanostructures, and is made possible by the superresolution capabilities of IR-PHI. The linewidths in the NW spectra range from 35 to 75 meV and, in several cases, are significantly below the limiting values predicted by the bulk Au Drude damping parameter. These linewidths imply long dephasing times, and are attributed to reduction in both radiation damping and resistive heating effects in the NWs. Compared to previous imaging studies of NW Fabry-Perot modes using electron microscopy or near-field optical scanning techniques, IR-PHI experiments are performed under ambient conditions, enabling detailed studies of how the environment affects mid-IR plasmons.