Quantum nanophotonics toolbox

Nano optics is concerned with the properties of light at the nanometer scale. Because of Abbes diffraction limit it is impossible to squeeze light in free space into volumes that are considerably smaller than the light wavelength (this is a few hundred nanometers). Within the realm of nano optics one couples light to metallic and dielectric nanoparticles, to excite them and to overcome the diffraction limit thereby localizing light in extreme sub-wavelength dimensions. Possible applications range from (bio)sensors over photovoltaics to optical data processing. The goal of this project is to incorporate quantum mechanical effects into the description of nano optics. We will develop a simulation toolbox, which will bridge between nano and quantum optics and constitutes a flexible platform for future investigation. The software to be developed in this project will be made freely available. On the one hand, we will develop routes towards the description of nano optics at the photon level, thus bridging between nano and quantum optics. Conceptually this step comes along with a number of difficulties, most importantly material losses (such as ohmic losses) inside the nanoparticles which hinder a direct quantization of the light fields. At the beginning of this project, we will investigate a number of possible approaches, which have been proposed in the recent literature and which are based on resonance mode expansions and effective models. At present the most suited approach is still unclear. On the other hand, we will investigate quantum mechanical effects in the description of the nanoparticles, namely in the form of modified boundary conditions at the material surfaces. The approach to be pursued is relatively old, the concept of the so-called Feibelman parameters has been developed in the 1970ies, but the approach has been generalized only recently to nanoparticles. In collaboration with a research team in San Sebastian, who obtain such Feibelman parameters from parameter-free quantum simulations for simple systems, we will use these parameters and incorporate them into simulations for realistic nanoparticles.