Dr. Christin David leads a junior research group in theoretical nanophotonics with focus on the optical response of hybrid nanostructures at the Institute of Condensed Matter Theory and Optics. She is a principal investigator of the DFG Collaborative Research Center (CRC) 1375 NOA on Nonlinear Optics down to Atomic scales. Dr. David has been working as a postdoctoral DFG fellow at DTU Fotonik, Denmark, and a Marie-Curie fellow at IMDEA Nanociencia, Spain.
The Junior Research Group on Theoretical Nanophotonics investigates optical properties of nanostructured systems from the nanometer to the device scale. Low symmetries, amorphous nanoparticle distributions and naturally rough interfaces and their linear and nonlinear optical response are investigated as an integral part of complex multilayers. Hereby, we develop analytic and numeric frameworks with a focus on semi-classical theories introducing advanced material and interaction models while maintaining the low computational cost of classical electrodynamics. Our research aims at an integrated, multiscale approach to photonic devices with hybrid, functionalized interfaces. Addressing these challenges will yield improved analytic and numerical schemes able to maintain the reliable and rapid methods of computational nanophotonics while extending its scope towards multiphysics aspects.
Nanostructured devices for spectroscopy, microscopy, photovoltaics and catalysis are investigated within classical electromagnetics, including properties of
Soft plasmonics in ionic fluids
Semi-classical charge interactions
Nonlinear and non-classical properties of amorphous multilayered heterostructures are investigated within the CRC 1375 NOA together with experimental groups at the Institute of Applied Physics in Jena.
Dr. David is actively involved in teaching theoretical physics courses and mathematical and computational methods for bachelor students and student teachers in physics, chemistry and photonics. Her specialized lectures for master and doctoral students concentrate on the theory and application of nanostructures in large scale optical devices.
Dr. David’s research team uses different methods from computational photonics to describe large scale optical devices with nanoscale features. The group has a strong expertise in linear and nonlinear response of metallic particles using numerical modelling based on semi-classical theories, Boundary Element Method (BEM) for arbitrarily shaped particles, Mie Theory for clusters of spherical particles and Fourier Modal Method (FMM) for complex layered structures.
Recents Research Results
Thin-walled nanotubes for Raman spectroscopy [1, 2]: Together with TU Dresden we investigate hollow nanotubes for Raman sensing. Our in-house FMM codes where extended to include analytical Fourier transforms of unit cells made from multilayered circular structures. We studied various geometrical parameters and modified the permittivity of the system to account for additional free electrons resulting from the electrochemical anodization process similar to low-level doping. Emphasis was put on describing the local field enhancement as a function of geometry, such as wall thickness and nanotube height, but also as a function of electron doping. Analytic expressions were found following Bragg’s law with effective geometrical parameters extracted from the FMM.
Nonclassical electron-electron interactions : We studied strong optical coupling of metal nanoparticles with dielectric substrates accounting for nonclassical interactions. Light-induced, mesoscopic electron dynamics significantly increase absorption and scattering cross sections for nanoparticles <20 nm. We observe a splitting of local optical modes spanning several tenths of nanometers. This is a signature of semi-classical, strong optical coupling via the dynamic Stark effect, known as Autler-Townes splitting. The photocurrent generated in this description is increased by up to 2%, which agrees better with recent experiments at WUST, Poland, then compared to identical classical setups with up to 6%.
Soft Plasmonics : Spatial interaction effects between charge carriers in ionic systems play a sizable role beyond a classical Maxwellian description. We developed a nonlocal, two-fluid, hydrodynamic theory of charges and studied ionic plasmon effects. Ionic spatial dispersion arises from both positive and negative charge dynamics with an impact in the far infrared. Despite highly classical parameters, nonlocal quenching of up to 90% is observed for particle sizes spanning orders of magnitude. Notably, the ionic system is widely tunable via ion concentration, mass and charge, in contrast to solid metal nanoparticles. A nonlocal soft plasmonic theory for ions is relevant for biological and chemical systems.