The field of nanophotonics concerns the study and manipulation of visible and near-IR light on length scales comparable to or smaller than its wavelength. In our group, we focus on metallic (plasmonic) nanoparticles. In particular, we study the absorption and emission of quantum emitters coupled to collective plasmonic resonances. We are interested in the strong coupling regime in which Plasmon-Exciton-Polaritons (PEPs), i.e., hybrid light-matter quasi-particles, emerge from the coupling of optical modes supported by resonant metallic nanoparticles (surface plasmon polaritons) and excitons in materials. We use arrays of metallic nanoparticles to tailor the coupling strength between surface plasmon polaritons and excitons and in this way control the characteristics of PEPs.
THz radiation are electromagnetic waves with frequencies in the range between microwaves and mid-IR. Resonant structures at THz frequencies formed by semiconductors or metals are important to control the propagation and enhancement of THz radiation. These structures respond very differently to incident radiation depending on their orientation and shape. In this way, the far- and near-field of incident radiation can be strongly modified by resonant structures, leading to enhanced or reduced extinction and to large local electromagnetic fields. We study these interactions both in the far- and in the near-field using THz time-domain spectroscopy and microscopy. Our goal is to tailor THz fields with subwavelength precision and to use these fields for THz spectroscopy. Optical pump-THz probe spectroscopic techniques enables the contact-free determination of the photoconductivity of materials. Therefore, we use these techniques to investigate materials relevant to energy applications.