Ultrafast spatially-inhomogeneous optical nonlinearities of metal nanostructures analyzed by ab-initio based Maxwell-Bloch equations

金属和混合纳米结构使人们能够在超短时间和纳米长度尺度上控制和设计电磁场。这些令人着迷的可能性是由于相关物质的基本激发和光场之间的相互作用而产生的。光-物质与纳米结构的相互作用取决于它们的形状，特别是在许多情况下，取决于所涉及的表面和界面的电子结构。例如，在靠近金属表面、边缘和角落的地方，由于自由运动电子的存在，磁场往往会得到强烈的增强。我们计划开发一种方法，能够在微观基础上描述金属和混合纳米结构的线性和非线性光电性质。我们将从从头算密度泛函理论出发，计算电子能带结构和波函数。这些结果将被用来建立材料动力学的Bloch型方程，该方程将与麦克斯韦方程进行数值自洽求解。我们的实空间运动方程方法对纳米尺度上的超快效应提供了详细的微观描述。所获得的理解将用于分析实验和开发新的设计概念。此外，我们的方法将被应用于光-物质动力学的相干控制技术，例如脉冲整形。

Metallic and hybrid nanostructures allow one to control and design electromagnetic fields on ultrashort time and nanometer length scales. These fascinating possibilities arise due to an interplay between the elementary excitations of the involved materials and the light field. The light-matter interaction with nanostructures depends on their shape and in many cases, in particular, on the electronic structure of the involved surfaces and interfaces. For example, close to metal surfaces, edges, and corners fields are often strongly enhanced due to the presence of freely moving electrons. We plan to develop an approach that is capable of describing the linear and nonlinear optoelectronic properties of metal and hybrid nanostructures on a microscopic basis. The starting point will be computations of the electronic band structure and wave functions via ab-initio density functional theory. These results will be used to set up Bloch-type equations for the material dynamics which will be solved numerically self-consistently with Maxwell’s equations. Our realspace equation of motion approach provides a detailed microscopic description of ultrafast effects on the nano scale. The gained understanding will be used to analyze experiments and for the development of novel design concepts. Furthermore, our approach will be applied to coherent control techniques of the light-matter dynamics by, e.g., pulse shaping.