Dynamics of Surface Plasmon Polaritons in Metal Nanowires

Metal nanostructures have found extensive use in a variety of applications in chemistry, including as substrates for molecular sensing and surface enhanced spectroscopy and as nanoscale heaters for photothermal therapy. These applications depend on the strong absorption and field enhancements associated with localized surface plasmon resonance (LSPR). This has led to a number of studies of how the LSPR line width, which measures energy losses for the coherent electron motion, depends on the size and shape of different types of metal nanoparticles, and the environment around the particle. Extended metal nanostructures, such as nanowires and nanoplates, display propagating surface plasmon modes, termed surface plasmon polaritons (SPPs), in addition to LSPRs. These modes are important for applications where metal nanostructures are used as waveguides. However, less is known about the damping of the propagating SPPs compared to the LSPRs. The energy losses for the propagating SPP modes can be investigated by measuring propagation lengths. The goal of this Feature Article is to review recent experiments that have provided quantitative information about the propagation lengths of SPPs in metal nanostructures, and to provide a physical understanding of the important factors in SPP damping.

金属纳米结构在化学的多种应用中得到了广泛使用，包括作为分子传感和表面增强光谱的基底，以及作为光热疗法的纳米级加热器。这些应用依赖于与局域表面等离子体共振（LSPR）相关的强吸收和场增强。这导致了许多关于LSPR线宽（其衡量相干电子运动的能量损失）如何取决于不同类型金属纳米粒子的尺寸和形状以及粒子周围环境的研究。延伸的金属纳米结构，如纳米线和纳米片，除了LSPR之外，还显示出传播的表面等离子体模式，称为表面等离子体激元（SPP）。这些模式对于将金属纳米结构用作波导的应用很重要。然而，与LSPR相比，人们对传播的SPP的阻尼了解较少。传播的SPP模式的能量损失可以通过测量传播长度来研究。这篇专题文章的目的是回顾最近提供了有关金属纳米结构中SPP传播长度的定量信息的实验，并对SPP阻尼的重要因素提供物理理解。