Lyvers David P, Moon Jeong-Mi, Kildishev Alexander V, Shalaev Vladimir M, Wei Alexander
Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA.
ACS Nano. 2008 Dec 23;2(12):2569-76. doi: 10.1021/nn8006477.
Hexagonal 2D arrays of Au nanorods support discrete plasmon resonance modes at visible and near-infrared wavelengths when coupled with light at normal incidence (k(z)). Reflectance spectra of nanorod arrays mounted on a thin Au baseplate reveal multiple resonant attenuations whose spectral positions vary with nanorod height and the dielectric medium. Simulations using 3D finite-element method calculations reveal harmonic sets of longitudinal standing waves in cavities between nanorods, reminiscent of acoustic waves generated by musical instruments. The nodes and antinodes of these quarter-wave plasmon modes are bounded, respectively, at the base and tips of the array. The number of harmonic resonances and their frequencies can be adjusted as a function of nanorod height, diameter-spacing ratio, and the refractive index of the host medium. Dispersion relations based on these standing-wave modes show strong retardation effects, attributed to the coupling of nanorods via transverse modes. Removal of the metal baseplate is predicted to result in resonant transmission through the Au nanorod arrays, at frequencies defined by half-wave modes within the open-ended cavities.
当与垂直入射光（k(z)）耦合时，金纳米棒的六边形二维阵列在可见光和近红外波长下支持离散的等离子体共振模式。安装在薄金基板上的纳米棒阵列的反射光谱显示出多个共振衰减，其光谱位置随纳米棒高度和介电介质而变化。使用三维有限元方法计算的模拟揭示了纳米棒之间腔体内纵向驻波的谐波集，让人联想到乐器产生的声波。这些四分之一波长等离子体模式的节点和波腹分别限制在阵列的底部和顶部。谐波共振的数量及其频率可以根据纳米棒的高度、直径间距比和主体介质的折射率进行调整。基于这些驻波模式的色散关系显示出强烈的延迟效应，这归因于纳米棒通过横向模式的耦合。预计去除金属基板会导致在开放腔体内由半波模式定义的频率下通过金纳米棒阵列的共振传输。
