Angle-independent plasmonic substrates for multi-mode vibrational strong coupling with molecular thin films
Angle-independent plasmonic substrates for multi-mode vibrational strong coupling with molecular thin films
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DOI：
10.1063/5.0039195
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发表时间：
2021-03-14
影响因子：
4.4
通讯作者：
Sheldon, Matthew
中科院分区：
文献类型：
--
作者：
Brawley, Zachary T.;Storm, S. David;Sheldon, Matthew
最近已经探索了基于等离子体共振的分子到光学腔的振动强耦合，因为等离子体近场可以在亚衍射限制体积中提供强耦合。这种场局部化使耦合强度最大化，这对于改变分子的振动响应并由此操纵化学反应至关重要。在这里，我们展示了一个角度无关的等离子体纳米盘基板，克服了传统的法布里-珀罗光学腔的局限性，因为该设计可以与基板表面上的所有分子强烈耦合，而不管分子取向如何。我们表明，等离子体基片提供了强耦合与C=O的振动拉伸的沉积膜的PMMA。我们还表明，等离子体共振的大线宽允许同时强耦合到两个，正交水对称和不对称的振动模式在一水硫酸铜薄膜沉积在基板表面上。建立了三耦合振子模型，分析了等离子体共振与这两种水模的耦合强度。通过对纳米盘直径的精确控制，通过模式系统地调谐等离子体共振，其中来自两种模式的拉比分裂作为等离子体频率的函数而变化，并且对于一定范围的直径同时实现与两种模式的强耦合。这项工作可能有助于进一步研究操纵分子的基态化学景观，同时扰动多个振动模式，并增加耦合强度在子衍射极限体积。
Vibrational strong coupling of molecules to optical cavities based on plasmonic resonances has been explored recently because plasmonic near-fields can provide strong coupling in sub-diffraction limited volumes. Such field localization maximizes coupling strength, which is crucial for modifying the vibrational response of molecules and, thereby, manipulating chemical reactions. Here, we demonstrate an angle-independent plasmonic nanodisk substrate that overcomes limitations of traditional Fabry-Perot optical cavities because the design can strongly couple with all molecules on the surface of the substrate regardless of molecular orientation. We demonstrate that the plasmonic substrate provides strong coupling with the C=O vibrational stretch of deposited films of PMMA. We also show that the large linewidths of the plasmon resonance allow for simultaneous strong coupling to two, orthogonal water symmetric and asymmetric vibrational modes in a thin film of copper sulfate monohydrate deposited on the substrate surface. A three-coupled-oscillator model is developed to analyze the coupling strength of the plasmon resonance with these two water modes. With precise control over the nanodisk diameter, the plasmon resonance is tuned systematically through the modes, with the Rabi splitting from both modes varying as a function of the plasmon frequency and with strong coupling to both modes achieved simultaneously for a range of diameters. This work may aid further studies into manipulation of the ground-state chemical landscape of molecules by perturbing multiple vibrational modes simultaneously and increasing the coupling strength in sub-diffraction limited volumes.