Our research aim is to control the optical properties of mesostructured assemblies by using rational design, self-assembly methods in combination with tailored plasmonic building blocks and optical characterization methods. Optical metasurfaces are artificially structured materials, which have a controlled heterogeneity on a length scale less than the wavelength of light. By using a rational design we can control the interaction of light with the nanostructured material, which leads to unprecedented functionalities. The tailored optical properties are of interest for a broad academic and industrial community for possible applications in the field of energy production (light harvesting, light concentrators), information technology (manipulation of light flow and storage, logic photonic circuits), stealth (optical cloaking, negative refractive index), and life sciences (physical and chemical sensing). There are well-established approaches for guiding the flow of light and tailoring its reflection using optical metasurfaces. However, this material class is limited by its elaborated top-down fabrication methods such as e-beam lithography or ion-beam milling (losses due to polycrystallinity, lack in resolution and scalability). Building up on those, we are using template-assisted self-assembly methods (bottom-up techniques) to obtain scalable mesostructured materials. Our research is dedicated to electromagnetic modeling, fabrication and characterization of novel functional system materials based on a unique combination of plasmonic and quantum emitter materials. We aim the creation of tailored system materials, by employing the interaction of different components, such as nanoparticles, nanostructures and functional polymers.


Freigeist Fellowship – A One-Way Road for Light

For the next generation of optical computing, a novel and cost efficient approach is needed. This future development requires both tailored control over nanometer-sized building blocks on large area and a fundamental understanding of the gain and loss mechanisms. In analogy to an electric diode, which conducts electron current in one direction, I will establish a one-way road for photons. Currently, practical demonstrations are scarce, and are limited in terms of how many devices may be fabricated in parallel. To realize fabrication on a larger scale, a synergy between optical metamaterials and colloidal self-assembly will be leveraged. This requires, on the one hand, applying concepts from optical metamaterials, which obtain their properties from their building blocks rather than from their constituent material; and, on the other hand, using pre-existing gain and loss building blocks, which form an organized structure on large area by reducing their free energy. The strategy is to use my experience in rational design, large area self-assembly of tailored building blocks and optical characterization in the unique research environment Dresden to fabricate cost-efficient, programmable and up-scalable photonic diodes. This state-of-the art and interdisciplinary study will combine elements from physics, chemistry and engineering to lead into a novel class of optical devices.

Wissenschaftsvermittlung und -kommunikation – Visualisierung des Nanokosmos

Eine „Einbahnstraße“ für Licht, d.h. eine optische Diode, ist das vorgeschlagene Grundbauelement für die nächste Generation von optischen Computern (Freigeist-Fellowship König). Wissenschaftliche Grundlagen, um solch eine optische Diode kosteneffizient und reproduzierbar herzustellen, sind kolloidale Konzepte sowie Symmetrieeigenschaften wie sie in der physikalischen Chemie und Physik betrachtet werden. Wichtig ist hierbei, dass die neue optische Eigenschaft durch die Strukturbildung (selbstassemblierten Verstärkungs- und Dämpfungsnanostrukturmaterialien) verursacht wird und nicht durch die Eigenschaften der einzelnen Komponenten. Solche komplexen optischen anisotropen Isolierungseffekte existieren nicht in natürlichen Materialien. Um den öffentlichen Diskurs an diesen Forschungen, ihren Ergebnissen und technischen Potenzialen zu beteiligen, ist eine Wissenschaftsvermittlung zwingend erforderlich.
• IPF Dresden: Tobias A.F. König, Dresden (Physikalische Chemie)
• TU Dresden: Manuela Niethammer (Didaktik der Chemie)
• Büro Schmalzriedt Karlsruhe: Sierk Schmalzriedt (Kommunikationsdesign)

Deutsche Forschungsgemeinschaft (DFG) – Research Grants

Coherent energy transfer in a self-assembled plasmonic lattice

In certain molecular aggregates, electronic excitations are coherently spread over the whole aggregate, as the individual transition dipole moments interact by dipole-dipole coupling. As this dipole-dipole coupling is a near-field effect, the interaction is limited to a small spatial region, and the participating quantum emitters cannot be addressed individually. We propose building a larger-scale analogue of a molecular aggregate to study coherent energy transfer. We will couple a small ensemble of quantum emitters with a spatially extended hybrid plasmonic lattice mode. The plasmonic features ensure localized hot spots with strong light-matter interaction, while the Bragg grating ensures a spatial size that allows optical addressing of the individual hot spots. Directed self-assembly of metallic nanoparticles with flat faces in regular arrays is necessary to obtain structures of high optical quality. However, directed self-assembly of these particles is challenging due to their dominant adhesion force, which tend to fix particles in place immediately upon contact with the target structure. Therefore, a precise surface modifications and controlled deposition of nanoparticles will be of critical importance during assembly of the plasmonic cavity lattice. Spatially resolved spectroscopy at the diffraction limit will allow us to map the wave function of the electronic excitation and its quantum correlations. In the end, the structure will act as a quantum simulator of the underlying molecular aggregate.
• Principle Investigators (PIs), Tobias A.F. König (IPF) and Markus Lippitz (Uni Bayreuth)

Plasmonic Organic Microcavity Laser

In this project, we aim to realize a novel concept for organic nanoparticle lasers. The goal is to understand the laser behavior of resonators combining plasmonic surface grating resonances with distributed Bragg reflectors. In preliminary work, we have shown that embedding metal nanoparticles and organic emitters in microcavities enables the realization of laser structures. Here, we aim to systematically investigate these novel structures. We aim to fabricate novel high definition noble metal nanoparticles with different sizes and shapes and realize periodic structures that exhibit surface lattice resonances. These will be combined with suitable organic materials and embedded in high Q Bragg reflector-based resonators to achieve excellent laser properties and, in particular, highly photostable emission systems. In analogy to a photon laser / distributed feedback laser (DFB), we aim to investigate the coherent energy transfer between surface grating resonance (open cavity design / optical feedback by Bragg scattering) and material gain. In addition, we want to investigate mechanically tunable surface grating resonances.
Principle Investigators (PIs), Tobias A.F. König, Andreas Fery (IPF) and Karl Leo (TU Dresden)

From Plasmonic Waveguides Towards Optical Modulators

In the first funding phase, we studied the energy propagation in plasmonic waveguides. Within these studies we obtained detailed understanding of the decay channels of lossy nanoparticle chains. In the interim phase, we will introduce gain materials (such as fluorophore, quantum dots, organic semiconductors) into the plasmonic waveguides. This will allow the compensation of losses, but as well introduces the option for optical modulations. Thus we will achieve the transition from waveguide material to optical modulator. We will perform simulations for rational design of plasmonic/semiconducting hybrid structures as well as experimentally characterize assemblies using (time resolved) optical spectroscopy.
• PI, Cluster of Excellence: Center for Advancing Electronics Dresden (cfaed), Biomolecular-Assembled Circuits (BAC) path.