Anna Kulter
Extreme ultraviolet (EUV) radiation is a key tool in ultrafast science, yet suitable optical components remain limited due to strong material absorption. Conventional EUV optics are largely based on reflective geometries, which limit achievable focal lengths and often introduce aberrations.
For my thesis, I designed and investigated a range of transmissive optical elements for EUV radiation, including gratings, lenses, focusing gratings, and polarizers. These devices are realized as metaoptics which are implemented as an array of holes with varying diameters in a thin silicon membrane, based on the vacuum-guiding principle. We hope that such transmissive EUV metaoptics will provide a route towards aberration- reduced optical systems and facilitate attosecond experiments with spatial resolution.
Eva Kogler
Computational materials design accelerates superconductivity research by guiding experiments, exploring broad chemical and structural spaces at low cost, and enabling controlled studies of thermodynamic conditions, such as pressure and composition, that are difficult to realize in the laboratory. Building on advances in first-principles methods and computing power, this presentation outlines a three-step workflow for conventional, phonon-mediated superconductors: (i) crystal structure prediction to identify thermodynamically stable candidate phases, (ii) calculation of normal-state properties (electronic structure, phonons, and electron-phonon coupling), and (iii) quantification of superconductivity via Migdal-Eliashberg theory or further approximations. In this talk, I will introduce the workflow and present selected results on crystal structure prediction, the role of anharmonic phonon contributions, and the prediction of the critical temperature and related observables.
Sandipan Borthakur
Young stars constantly accrete material from their protoplanetary disks. This accretion can alter the chemical composition of the stellar photosphere, which can be measured through high-resolution stellar spectroscopy. The stellar composition, therefore, serves as a tracer of the composition of the accreting material, which comes from the inner regions of the disk. Because the inner disk is the site of rocky planet formation, understanding its composition and evolution is crucial for planet formation theories. Direct measurements of inner disk compositions, however, remain observationally challenging. In this talk, I will present the observational and theoretical work I conducted during my PhD, which uses stellar photospheric abundances to constrain the composition of inner protoplanetary disks, and discuss what accretion signatures reveal about the chemical evolution of the inner protoplanetary disk.
Florian Küstner
Semiconductors provide the platform for light energy harvesting, light detecting and light emitting devices. Typically, charge separation in such devices is achieved through a pn-junction, however, metal-semiconductor junctions, so called Schottky junctions, show very similar properties and might be advantageous for some applications. As the lack of organic ligands results in their efficient photoelectric response, perovskite-capped PbS quantum dots are a promising semiconductor candidate for such devices. Spin coating of a solution of such quantum dots allows to create very thin and compact semiconductor layers on conducting electrodes. Photocurrent measurements with a photo-conductive atomic force microscope tip on the resulting ultrathin double Schottky junctions reveal the photocurrent dependency on the applied light intensity and the applied bias voltage. On the one hand, the precise knowledge of the photocurrent dependency on the local light intensity allows for two-dimensional intensity mapping of light with sub-optical resolution. On the other hand, bias sweeps on nano-structured gold substrates allow to distinguish between contributions from photo-excited charges in the quantum dot layer and hot charges in the gold electrode. By comparison with calculations, the latter can be attributed primarily to d-band holes, which are generated from plasmon decay through direct interband transitions in gold.
Sunny Laddha
Magnetic fields are one of the most fundamental quantities in various space disciplines, such as space weather studies, space plasma physics and planetology. The fluxgate magnetometer – a classical measurement device – requires periodic in-flight calibration of the offsets, which drift with time and due to temperature variations. In some scientific missions, the calibration reference is provided by optically pumped magnetometers. A recent example, fully developed and built in Graz, is the “Coupled Dark State Magnetometer” (CDSM), which uses a quantum-interference effect in rubidium atoms to derive the magnetic field strength from fundamental atomic properties. This talk will present ongoing developments of an optical vector magnetometer, which is based on the compensation of the ambient magnetic field to derive the vector components, using the Hanle effect in rubidium atoms as a sensitive and stable zero-field marker. Laboratory models outperforming state-of-the-art fluxgate magnetometers in sensitivity and stability will be shown, as well as a roadmap for a combined, self-calibrating CDSM and Hanle magnetometer.
Jakob Bancalari: Attosecond Beamline for the Investigation of Charge Carrier Dynamics in Solids
Patricia Magdalena Brugger: Fs time-resolved observation of charge- and energy transfer in structured organic semiconductors
Elias Henögl: Hydrogen Adsorption Storage in Porous Solid Materials
David Kneidinger: Large-Scale Organized Storms (MCSs) under Climate Change over Europe
Niko Koch: Analysis and Classification of Non-Exhaust Particles Emissions by Combining Microscopy, Spectroscopy and Machine Learning
Wolfgang Lakata: Design and characterization of a high signal-to-noise ratio 40 kHz multiplex SFG-VS spectrometer
Xaver Landerl: Ab-Initio modelling of molecules of surfaces
Dominik Spath: IsoME: Streamlining High Precision Eliashberg Calculations
Nadine Trummer: Machine Learning for Space Debris Characterization
Florian Unterkofler: Modelling heat transport in complex materials using machine-learning approaches
Valentin Weis: STREAM: STorylines of Danube stREAMflow – Assessing future streamflow for different atmospheric circulation responses to greenhouse gas forcing
Alexander Sagar Grossek
We built a modular cross-polarized pump-probe beam line, including high harmonic generation (HHG) which enables a sub-femtosecond pulse to be used as the pump, and a part of the driving IR femtosecond pulse used as the probe. The IR pulse is carrier-envelope-phase (CEP) stabilized which determines the pulse shape. The high-harmonic sub-femtosecond pulse is used to gate the IR pulse in a gaseous medium. The electron wave-packet generated by ionization via the HHG has the same sub-femtosecond temporal properties. This electron wave is streaked by the IR pulse. Recording the streaking current across a range of delays with pump and probe beams gives a CEP dependent visualization of the driving IR pulse feld oscillations. Furthermore, we attempt to excite coherent superpositions of Rydberg eigenstates in gaseous media and seek to measure beating oscillations of these superpositions through subsequent ionization by the probe beam in an identical measurement methodology to the streaking technique mentioned above. Additionally, we inspect the process of spectral broadening in gas-flled hollow-core-fber via self-phase-modulation and pulse compression for intermediate laser pulse repetition rates in the low 100 kHz region.
Moritz Theissing
Recrystallization, together with recovery and grain growth, plays a crucial role in controlling the microstructure and resulting properties of wrought aluminum alloys. As these processes occur rapidly and are infuenced by numerous internal and external factors, their investigation remains challenging.
The aim of this study was to evaluate diferent characterization techniques for investigating recrystallization in aluminum alloys. Cold-rolled AA8079 foil stock was examined using two approaches: ex situ annealing combined with EBSD and hardness measurements, and in situ annealing combined with EBSD. The results show that both approaches lead to similar recrystallization behavior and comparable fnal microstructures. In situ experiments allow recovery, recrystallization, and grain growth to be observed within a single experiment, but provide limited statistical signifcance. Ex situ methods, in contrast, ofer large, high-resolution datasets, though they require multiple samples subjected to diferent heat-treatment conditions, which is a drawback.
These fndings were then applied to the study of recrystallization in other aluminum alloys. The infuence of dispersoids on recrystallization and grain growth was investigated in two AlMgZnCu crossover alloys, with dispersoids present in only one alloy. While dispersoids strongly suppress grain growth, they have little efect on recrystallization or nucleation. Finally, the recrystallization behavior of an ultrafne-grained AA6061 alloy was examined using in situ EBSD and compared with in situ TEM.
Felix Hitzelhammer
Modern quantum photonic technologies demand numerical methods capable of accurately simulating light-matter interactions at the microscopic level. In general, this requires a fully quantum description of both the electromagnetic field and the material degrees of freedom. However, such simulations rapidly become computationally intractable due to the exponential scaling of the Hilbert space. Conversely, classical electromagnetic solvers are computationally efficient but fail to capture intrinsically quantum features such as photon statistics and nonclassical correlations.
To bridge this gap, we present a stochastic framework that incorporates quantum constraints arising from operator non-commutativity into classical electromagnetic simulations. Using stochastic differential equations, we imprint the dynamics of an optically driven two-level system onto spatiotemporal classical fields that can be coupled directly to time-domain Maxwell solvers. This approach enables the calculation of photon correlations from classical electromagnetic fields.