Confinement of light to nanoscale dimensions provides the unique opportunity to increase light-matter interaction for various application, such as chemical sensing, super-resolution imaging, or miniaturized photonic circuitry. In the infrared spectral range, this can be achieved by employing lattice vibrations in polar dielectric crystals – optical phonons – to form phonon-polaritons, which allow tight spatial confinement due to their large momenta.
The Lattice Dynamics group develops new infrared nanophotonic concepts and experimental methods to probe the properties of phonon polaritons confined to surfaces, in heterostructures, and in nanostructures. Specifically, we use Otto-type prism coupling, second harmonic and sum-frequency generation spectroscopy, as well as sum-frequency generation microscopy, providing a comprehensive understanding of the polaritonics systems. Enabling these experiments, the group employs the widely tunable FHI free-electron laser (FEL) as a uniquely powerful infrared light source. These experimental capabilities are complemented by theoretical spectroscopy toolbox, that not only allows theoretical description of the experimental results but also enables predictive studies of yet unexplored polariton physics in new materials and nanostructures.