Cherqui Charles, Li Guoliang, Busche Jacob A, Quillin Steven C, Camden Jon P, Masiello David J
Department of Chemistry, University of Washington , Seattle, Washington 98195, United States.
Center for Electron Microscopy, Institute for New Energy Materials & Low-Carbon Technologies, School of Materials Science and Engineering, Tianjin University of Technology , Tianjin 300384, China.
J Phys Chem Lett. 2018 Feb 1;9(3):504-512. doi: 10.1021/acs.jpclett.7b03271. Epub 2018 Jan 16.
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 ∼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 system's 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.
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、信息和能源科学等广泛应用具有实际重要性。例如，不仅能够轻松调节等离子体光谱，还能调节与光和/或热的耦合程度、品质因数和光学模式体积，这将有助于依赖等离子体元件在纳米尺度上限制和操纵光的纳米光子器件和分子传感器的性能和功能。虽然存在许多调节这些特性的途径，但识别新方法——尤其是当它们易于通过实验应用时——是一项重要任务。在这里，我们展示了衬底厚度和介电成分对等离子体杂交以及依赖于这种杂交的下游特性可能产生的重大且未被充分认识的影响。我们发现，即使是薄至约10 nm的衬底也能显著混合自由空间等离子体模式，使暗模式具有明亮特性（反之亦然），从而改变等离子体态密度以及系统的近场和远场光学特性。结合电子能量损失谱（EELS）实验、数值模拟和分析模型，以阐明单个银纳米立方体的偶极、四极和八极角局域等离子体共振在有限衬底诱导混合中的这种行为。
