Multimodal Tip-Enhanced Nonlinear Optical Nanoimaging of Plasmonic Silver Nanocubes.
Multimodal Tip-Enhanced Nonlinear Optical Nanoimaging of Plasmonic Silver Nanocubes.
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DOI：
10.1021/acs.jpclett.1c03196
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发表时间：
2021-09
期刊：
影响因子：
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通讯作者：
Chih-Feng Wang;P. El-Khoury
中科院分区：
文献类型：
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作者：
Chih-Feng Wang;P. El-Khoury
在等离子体尖端-样品纳米结处的光场局部化已经使得能够通过尖端增强线性光学光谱进行高空间分辨率化学分析，包括拉曼散射和光致发光。在这里，我们说明了非线性光学过程，包括参量四波混频（4 WM），二次谐波/和频产生（SHG和SFG），和双光子光致发光（TPPL），可以增强在等离子体结和空间光谱解决同时与几nm的空间分辨率在环境条件下。通过我们的光谱nanoimages的详细分析，我们发现，当地的非线性信号的效率是由尖样品结共振，在几个纳米的长度尺度上变化。即，通过TPPL跟踪以不同非线性信号为中心或周围的等离子体共振，并且发现它们选择性地增强具有紧密匹配的光学共振的非线性信号。
Optical field localization at plasmonic tip-sample nanojunctions has enabled high-spatial-resolution chemical analysis through tip-enhanced linear optical spectroscopies, including Raman scattering and photoluminescence. Here, we illustrate that nonlinear optical processes, including parametric four-wave mixing (4WM), second-harmonic/sum-frequency generation (SHG and SFG), and two-photon photoluminescence (TPPL), can be enhanced at plasmonic junctions and spatiospectrally resolved simultaneously with few-nm spatial resolution under ambient conditions. Through a detailed analysis of our spectral nanoimages, we find that the efficiencies of the local nonlinear signals are determined by sharp tip-sample junction resonances that vary over the few-nanometer length scale. Namely, plasmon resonances centered at or around the different nonlinear signals are tracked through TPPL, and they are found to selectively enhance nonlinear signals with closely matched optical resonances.