A5 – Nonlinear and nonlocal optical response in complex nanostructured multilayers

This project investigates the nonlinear optical response stemming from nanosized features in complex, multilayered structures. Light-matter coupling at the ultimate nanometer scale can strongly influence the optical properties of a large structure through interaction with lattice modes and retardation. Some of the remaining challenges that computational nanophotonics faces today are

• structures with low symmetries, such as amorphous composites and random particle distributions,
• the description of realistic interfaces accounting for surface roughness,
• the efficient introduction of quantum effects into classical electrodynamics methods, and
• nonlinear properties of complex systems, which are not sufficiently investigated.

The particle size and layer thickness in the systems under investigation are of a few nanometers only. Therefore, we need to extend standard models with short-ranged electron-electron interaction effects, in particular, in metal components. The ability to reliably describe interaction effects and the corresponding near-field response on multiple scales, ranging from an accurate quantum limit at nanostructured interfaces to the device scale, is essential for the design and optimization of technologies exploiting complex materials and composites with functionalized surfaces. Addressing these challenges is the central aim of this project.

We aim at developing theoretical models and numerical methods to describe the nonlinear optical response of ultrathin multilayered structures and amorphous composites from particles embedded in a host material. Furthermore, we plan to account for additional surface scattering at realistic interfaces from surface roughness. In order to realistically describe these rough surfaces on the atomic scale, we will utilze molecular dynamics calculalions. Simulations are performed in strong collaboration with the experimental efforts in CRC projects B3 and B4. Project A5 will yield analytic and numeric schemes able to maintain the reliable and rapid methods of computational nanophotonics while extending their scope towards multiphysics and multiscale aspects.