Optical Properties of Metallic Waveguide Structures at the Nanoscale

粒子等离子体激元和表面等离子体激元分别是金属粒子或金属表面上电荷分布和电磁场的集体激发。最近在金属的微米和纳米结构方面的进展允许对等离子体特性进行前所未有的定制，特别是它们与光相互作用的方式。这为使用结构化金属作为纳米级光子学和电子器件的常见构建块提供了机会。金属中的电荷激发对外部光场的响应是非局域的。从技术上讲，这是由于电荷激发运动方程中的梯度项，最终是由于电荷守恒。虽然在体系统中，这种非定域性通常可以忽略不计，但它在金属纳米结构中确实变得重要，因为它们的空间尺寸往往是几十纳米的量级，最小的特征通常小于10 nm，因此引入了新的长度尺度，小于光波长，为了正确描述这种系统的动力学特性，必须考虑金属中的电荷分布以及电磁场。此外，由于纳米结构系统中电荷的积累，在强光场中的非线性响应效应变得增强。本计画的目标是利用数值技术，发展一个一致的金属奈米结构非局部与非线性反应效应的微观描述。等离子体激元动力学的经典和量子力学模型将被耦合到麦克斯韦方程组，这是使用有限差分时域方案处理。

Particle plasmons and surface plasmon polaritons are collective excitations of charge distributions and the electromagnetic field in metal particles or at metallic surfaces, respectively. The recent progress in micro- and nano-structuring of metals allows an unprecedented tailoring of the plasmon properties, in particular the way they interact with light. This opens an opportunity to use structured metals as common building blocks of photonics and electronics devices at the nanoscale. The response of the charge excitations in a metal to an external light field is nonlocal. This results technically from gradient terms in the equations of motion of the charge excitations and is ultimately due to the conservation of charge. While in bulk systems this nonlocality is, in general, negligible, it does become important in metallic nano-structures, because their spatial dimensions tend to be of the order of a several tens of nanometers with smallest features often smaller than 10 nm and, thus, introduce new length scales, smaller than the light wavelength, on which the charge distributions in the metal as well as the electromagnetic fields must be considered in order to obtain a correct description of the dynamics in such systems. Furthermore, nonlinear response effects in strong optical fields become enhanced due to charge accumulation in the nanostructured systems. The goal of this project is to develop a consistent microscopic description of nonlocal and nonlinear response effects in metallic nano-structures using numerical techniques. Classical and quantum mechanical models of plasmon dynamics will be coupled to Maxwell's equations, which are treated using the finite-difference time-domain scheme.