We work on the fundamentals of light-matter interactions in nanostructured materials, from the visible to the mid-infrared part of the spectrum. A particular focus lies on plasmonic and dielectric nanoantennas, coupling to low-dimensional materials, and the study of quantum phenomena.
We work on the fundamentals and applications of a new class of all-dielectric metasurfaces based on the physics of bound states in the continuum (BIC). Leveraging their ultrasharp resonances and strong nanophotonic enhancement, we explore tailored light-matter interactions with a special focus on new platforms for sensing and biospectroscopy.
Van der Waals materials and 2D materials comprise a versatile toolkit for our research. The weak Van der Waals forces between adjacent layers of the materials allow for a mechanical isolation of few to single-atom thick crystals, as well as the stacking of different materials and the combination of their properties.
In our group we utilize these mechanics to fabricate novell photonic structures e.g. for the investigation of light-matter coupling.
We investigate a range of processes in unexplored materials and nanostructures that happen on sub-nanosecond timescales. With an ultrafast pump-probe setup, we monitor the effects of a pump pulse on a medium by sending a second pulse with a variable time delay. This allows us to study phenomena from the nanosecond timescales of acoustic phonons in nanoantennas, over picosecond electronic decays down to instantaneous processes like sum frequency or harmonic generation. By tayloring novel nanostructure designs in combination with efficient materials, we aim to increase the yield in these processes, for future applications in ultrafast optical signal processing.
We work with scattering scanning optical near-field microscopy (s-SNOM), an imaging technique able to break the diffraction limit and observe objects with nanometer resolution, using mid-infrared light. By shining a laser onto the apex of a metallic AFM tip, the highly confined and spatially localized fields around the scanning probe allow for surface-sensitive spectroscopic analysis of a sample surface. We use this technique mainly for two research areas: the characterization of bound states in the continuum and biospectroscopy of living cells and other biological material such as lipids.
The former entails the imaging and spectroscopic analysis of periodic dielectric structures with very high quality factors and narrow, tunable resonances. The latter encompasses work on living cells such as Ecoli and lung cancer cells, as well as photoswitchable lipids, with an emphasis on the dynamic processes that can be observed in such a system. We are currently developing the first microfluidic flow cell for s-SNOM, with the intention to combine the (until now) distinct domains of near-field microscopy and biophysics.
Semiconducting nanoantennas consisting of silicon, germanium, or gallium phosphide enable us to enhance nonlinear optical processes by many orders of magnitude. Electric, magnetic and toroidal electromagnetic modes confine electromagnetic fields in a controlled manner. These properties are also very valuable for surface-enhanced spectroscopies without high optical losses.
On the other hand metallic nanostructures, called plasmonic nanoantennas, enable us to confine optical fields deep below the diffraction limit, over distances of only a few cubic nanometers. Molecules or quantum matter experiencing these enhanced fields show a vast increase in their interactions which photons. We exploit this for surface-enhanced optical spectroscopies.