Gap-Plasmon-Enhanced Nanofocusing Near-Field Microscopy
Gap-Plasmon-Enhanced Nanofocusing Near-Field Microscopy
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DOI：
10.1021/acsphotonics.5b00438
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发表时间：
2016-02-01
期刊：
影响因子：
7
通讯作者：
Lienau, Christoph
中科院分区：
文献类型：
--
作者：
Becker, Simon F.;Esmann, Martin;Lienau, Christoph
报道了在纳米聚焦扫描近场光学显微镜中观察到的纳米尺度带隙区域的相干光散射。当接近一个纳米聚焦的金锥体到一层薄的半透明金膜的表面并在透射中进行检测时，我们发现在k空间中选择的近场信号的散射强度在最后5 nm处急剧增加。通过与有限元模拟的详细比较，证实了这是一个高度受限的带隙等离子体的特征。模拟结果表明，通过基本的探头样品距离控制方案，约束是可调的，甚至可以调整到远低于锥形尖端半径的水平。这种受控的GaP等离子体激元的实验实现及其在扫描探针显微镜中的特征提取为在单纳米尺度及以下的宽带光谱铺平了道路，例如在瞬时吸收或二维光谱中使用多波长的并行检测。
We report the observation of coherent light scattering from nanometer-sized gap regions in a nanofocusing scanning near-field optical microscope. When approaching a nanofocusing gold taper to the surface of a thin semitransparent gold film and detecting in transmission, we find a steep increase in scattering intensity over the last 5 nm in a near-field signal selected in k-space. This is confirmed as a signature of highly confined gap plasmons by detailed comparisons to finite element method simulations. The simulations reveal that the confinement is adjustable via the underlying probe sample distance control scheme even to levels well below the taper apex radius. This controlled experimental realization of gap plasmons and the extraction of their signature in a scanning probe microscope pave the way toward broadband spectroscopy at and below single-nanometer length scales, using parallel detection at multiple wavelengths, for instance, in transient absorption or two-dimensional spectroscopy.