Multipolar Nanocube Plasmon Mode-Mixing in Finite Substrates
Multipolar Nanocube Plasmon Mode-Mixing in Finite Substrates
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DOI：
10.1021/acs.jpclett.7b03271
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发表时间：
2018-02-01
影响因子：
5.7
通讯作者：
Masiello, David J.
中科院分区：
文献类型：
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作者：
Cherqui, Charles;Li, Guoliang;Masiello, David J.
轻松控制等离子体纳米结构的辐射和非辐射特性对于生物、化学、光学、信息和能源科学的广泛应用具有实际意义。例如，不仅能够轻松调节等离激元光谱，而且能够轻松调节与光和/或热的耦合程度、品质因数和光学模式体积，这将有助于纳米光子器件和分子传感器的性能和功能，这些器件和分子传感器依赖于等离激元元件来限制和操纵纳米级的光。虽然存在许多调整这些特性的途径，但识别新方法（尤其是当它们易于实验应用时）是一项重要任务。在这里，我们证明了基板厚度和介电成分对等离激元杂交以及依赖于这种杂交的下游特性的显着且未被充分认识的影响。我们发现，即使是薄至 10 nm 的基板也可以非同寻常地混合自由空间等离子体模式，为黑暗的模式赋予明亮的特性（反之亦然），从而改变等离子体状态密度以及系统的近场和远场光学特性。电子能量损失光谱（EELS）实验、数值模拟和分析模型相结合，用于阐明单个银纳米立方体的偶极子、四极子和八极角局域等离子体共振的有限基底诱导混合中的这种行为。
Facile control of the radiative and nonradiative properties of plasmonic nanostructures is of practical importance to a wide range of applications in the biological, chemical, optical, information, and energy sciences. For example, the ability to easily tune not only the plasmon spectrum but also the degree of coupling to light and/or heat, quality factor, and optical mode volume would aid the performance and function of nanophotonic devices and molecular sensors that rely upon plasmonic elements to confine and manipulate light at nanoscopic dimensions. While many routes exist to tune these properties, identifying new approaches-especially when they are simple to apply experimentally-is an important task. Here, we demonstrate the significant and underappreciated effects that substrate thickness and dielectric composition can have upon plasmon hybridization as well as downstream properties that depend upon this hybridization. We find that even substrates as thin as similar to 10 nm can nontrivially mix free-space plasmon modes, imparting bright character to those that are dark (and vice versa) and, thereby, modifying the plasmonic density of states as well as the systems near- and far-field optical properties. A combination of electron energy-loss spectroscopy (EELS) experiment, numerical simulation, and analytical modeling is used to elucidate this behavior in the finite substrate-induced mixing of dipole, quadrupole, and octupole corner-localized plasmon resonances of individual silver nanocubes.