Tuesday 4:30 pm (Freiburg) / 7:30 am (Vancouver)
(except for 14.10. and 21.10. On those days: 30 minutes later)
14.10.25 – Adrian Kirchner, TU Graz
04.11.25 – Grigorios Boulogiannis, Fraunhofer ISE Freiburg & Alexander Döring, University of Stuttgart
11.11.25 – Philipp Lunt, University of Heidelberg
25.11.25 – Info event for PhD students
02.12.25 – David Busto, Lund University, Sweden
09.12.25 – Workshop on „Choosing Career Paths after PhD“
16.12.25 – Patrick Rupprecht, Lawrence Berkeley National Laboratory, USA
13.01.26 – Federico Belli, Heriot-Watt University, UK
20.01.26 – Julia Gessner, University of Heidelberg
27.01.26 – Alexander Horn, Hochschule Mittweida, University of Applied Sciences
03.02.26 Johan Mauritsson, Lund University, Sweden
03.02.26 Johan Mauritsson, Lund University, Sweden
From attosecond science to migraine studies with fMRI via opera
In this presentation I will demonstrate how basic research, when presented as popular science, can lead to new insights and new research directions. The Nobel prize in physics 2023 was awarded to Pierre Agostini, Ferenc Krausz and Anne L’Huillier: “for experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter”. The attosecond pulses are generated through high-order harmonic generation with light. Already in the Nobel press release the analogy with music was made. Harmonics from light is unusual, but harmonics (and overtones) on sound is familiar to most. During the last two years we have used opera to introduce attosecond physics to a broad audience. We have also use magnetic resonance imaging to image a singing opera singer. This in turn connects to a study to see if flickering light may induce migraine. The current transition to LED lighting may cause migraine in a large fraction of the population if not handled correctly.
Chair: Giuseppe Sansone
27.01.26 – Alexander Horn, Hochschule Mittweida, University of Applied Sciences
Modification dynamics of metallic and semiconductor surfaces induced by ultrafast laser radiation
Using time-resolved optical metrology in combination with process modeling we try to get an understanding of laser ablation of matter using ultrafast laser radiation. In this presentation an overview on our investigations on the ablation of thin gold films using ultrafast laser radiation are presented. Applying time resolved interferometry and reflectometry complementary with hydrodynamics (TTM-HD) and molecular dynamics (TTM-MD) modeling, we are able to describe the ablation process more consistently. An outlook on first experimental results irradiating bulk silicon complete this presentation.
Chair: Jale Schneider
20.01.26 – Julia Gessner, University of Heidelberg
Tracing charge carrier and spin dynamics in solids from attosecond to picosecond time scales
The development of next-generation, energy-efficient, and environmentally friendly technologies depends critically on the discovery of new functional materials and a deep understanding of their fundamental properties. For optoelectronic and spintronic applications, optimizing material performance requires detailed optical characterization and insight into the complex interaction between light and matter. In particular, resolving ultrafast processes is essential for improving device efficiency and guiding future material design.
In the first part of this talk, we will explore charge carrier and spin dynamics in the attosecond time regime, focusing on the coherent response of a metallic film illuminated by a few-cycle, strong optical electric field. We will show how this thin ferromagnetic film can transiently exhibit a negative refractive index and superluminal pulse propagation, and how sub-cycle demagnetization dynamics emerge via optical inter-site spin transfer (OISTR).
In the second part, we will turn to the transient electronic and magnetic properties of hybrid metal halide perovskites, a promising class of materials for optoelectronic and spintronic devices. Using a novel ultrafast holographic microscope, we will investigate the femtosecond-to-picosecond time window in which coherence is lost and scattering processes begin to dominate material behaviour. We will examine charge carrier and spin diffusion and elucidate the connection between material morphology and optically induced electronic and magnetic inhomogeneities.
Chair: Lukas Bruder
13.01.26 – Federico Belli, Heriot-Watt University, Edinburgh, UK
Gas-filled hollow-core fibers: a wonderland for nonlinear optics
Hollow-core fibers, when filled with gases, become a dream playground for nonlinear optics, offering an exceptional level of control over dispersion, nonlinearity, and light–matter interaction. By driving these waveguides with ultrashort laser pulses, it is possible to shape light in ways that are difficult to achieve in conventional systems, including the generation of sub-cycle infrared pulses and few-cycle tunable ultraviolet pulses across the 100–400 nm spectral range.
In this talk, I will present this nonlinear optics “wonderland,” introducing the two main hollow-core fiber platforms, capillaries and anti-resonant fibers, and discussing how their guiding and dispersion properties influence nonlinear light generation. I will focus on two key processes, soliton dynamics and four-wave mixing, and show how they can be used to build widely tunable light sources tailored to different ad hoc spectroscopic needs.
I will conclude by highlighting ongoing work in the LUPO group and briefly outlining our current collaborative scientific and industrial efforts.
Selected publications
Optica 2 (4), 292-300 (2015)
Nature Photonics 13 (8), 547-554 (2019)
Optics Letters 44 (22), 5509-5512 (2019)
Nature Communications 13, 3536 (2022)
Chair: Lukas Bruder
16.12.25 – Patrick Rupprecht, Lawrence Berkeley National Laboratory, USA
Attosecond four-wave-mixing spectroscopy
Merging multidimensional spectroscopy with attosecond science is a powerful approach to disentangle complex quantum dynamics on fastest time scales. Four-wave-mixing (FWM) spectroscopy, where a weak attosecond extreme ultraviolet (XUV) pulse is mixed with two intense femtosecond infrared/visible pulses, constitutes a table-top implementation thereof. In this talk, I will discuss recent FWM work conducted in Berkeley concerning the measurement of ultrafast quantum state lifetimes in helium [1] and xenon [2] directly in the time domain. Furthermore, I will outline future directions of attosecond FWM, specifically tracing electronic coherences in photochemistry [3] and all-optical logic switching of XUV light [4]. This highlights the potential of table-top FWM for attosecond coherent control and ultrafast quantum technology.
[1] Rupprecht, Puskar, et al. Phys. Rev. Res. 6, 043100 (2024).
[2] Puskar, Rupprecht, et al. J. Chem. Phys. 163, 184302 (2025).
[3] Rupprecht, Montorsi, et al. Phys. Rev. Lett. 135, 233201 (2025).
[4] Rupprecht, et al. arXiv:2510.00699 (2025).
Chair: Giuseppe Sansone
02.12.25 – David Busto, Lund University, Sweden
Ultrafast quantum photoelectronics
The interaction of high energy light with matter leads to the emission of electrons in a process known as photoionization. This process underpins numerous measurement techniques in atomic and molecular physics, and material science to study the structure and properties of matter.
Despite the inherently quantum nature of the photoionization process, existing photoelectron-based measurement techniques mostly rely on measuring the classical momentum of the emitted electrons, overlooking fundamental quantum aspects of the photoionization process. The emergence of a new research field at the interface of attosecond physics and quantum information offers the opportunity to revisit the photoionization process to develop photoelectron-based quantum metrology. In this this talk I will first present advances in photoelectron quantum state tomography before discussing recent experiments illustrating how ultrafast photoionization could serve as a novel platform for testing quantum mechanics.
Chair: Benjamin Steiner
11.11.25 – Philipp Lunt, University of Heidelberg
Quantum Hall states with rotating atoms – a voyage into the vortex
The fractional quantum Hall effect exhibits topologically ordered phases of matter resulting from the interplay of strong magnetic fields and interactions – many of which are famously described by Laughlin’s celebrated wavefunction. Ultracold neutral atoms in synthetic magnetic fields offer a promising platform to explore the microscopic origins of these states, thanks to their unparalleld control over interactions, as well as the manipulation and detection of individual particles.
Here, we showcase the realization of a Laughlin state with two rapidly rotating spinful fermions in an optical tweezer [1,2]. Utilizing our single-atom and spin-resolved imaging technique, we reveal its defining signature: suppression of inter-particle interactions due to a vortex distribution in the particles’ relative motion. Building upon this work, we extend our system to larger particle numbers, realizing a two-component integer quantum Hall (IQH) state comprised of three fermions in each spin state. This brings us in reach of studying the emergence of quantum phase transitions between IQH states of weakly interacting fermions and FQH states of interacting bosons, enabled via a Feshbach resonance to tune the inter-particles interactions [3].
[1] P. Lunt et al. Phys. Rev. Lett. 133, 25340 (2024)
[2] P. Lunt et al. Phys. Rev. A 110, 063315 (2024)
[3] G. Möller et al. PRL 99, 190409 (2007)
Chair: Andreas Buchleitner
04.11.25 – Grigorios Boulogiannis, Fraunhofer ISE Freiburg & Alexander Döring, University of Stuttgart
Grigorios Boulogiannis:
Advancing Laser Processing Technology In Photovoltaics; Investigating the Linear and Nonlinear Optical Properties of Materials used in Photovoltaic Application
Laser processing plays a pivotal role in advancing materials used in the photovoltaic (PV) industry, aiming to improve efficiency, durability, and cost-effectiveness of solar technologies. Materials such as glasses, silicon carbide, and perovskites are of particular importance due to their optical, electrical, and structural properties. Ultrafast laser techniques enable precise modification of these materials through linear and nonlinear light–matter interactions, allowing for tailored surface and bulk functionalities. However, to fully harness the potential of such laser-based processes, a fundamental understanding of the linear and nonlinear optical absorption mechanisms governing these materials is essential. Gaining deeper insight into these interactions has the potential to facilitate the optimization of laser processing strategies and contribute to the development of next-generation photovoltaic devices.
Chair: Jale Schneider & Giuseppe Sansone
Alexander Döring:
Correlation measurements and simulations of light emitted by hot vapor microcells
This thesis is part of ongoing work to create a single-photon source based on thermal rubidium vapor in a thin microcell. The fundamental idea behind this concept consists in confining the excitation volume to a region smaller than the Rydberg blockade of an excited atom. The commonly used way to characterize non-classical light fields, such as a single photon source, is to measure the statistics of the photon flux via correlation measurements. Under specific circumstances, experimental noise and jitter can distort the measured correlations.
For a detailed examination of these effects, a numerical tool that can produce time stamps of a photon stream obeying an arbitrary given g(2) correlation function is developed, and its capabilities and limitations are discussed. Furthermore, a fundamental simulation framework for the four-wave mixing (FWM) experiment is set up, therefore allowing the
direct measurement of the influence on the g(2) correlation function of applying arbitrary effects on the photon stream.
Since current correlation measurements in the examined pulsed FWM scheme show no evidence of anti-bunching, this thesis investigates possible root causes via simulation and spectroscopic studies.
With the aforementioned tools, the influence of timing and width of the correlation window chosen for each pulse is simulated. It is shown that while they can strongly distort results when measuring on steep pulse flanks in a jitter-prone setup, correlation windows spanning large parts of the pulse around its maximum intensity precisely lead to the expected statistics.
The spectroscopic analysis is centered around fluorescence measurements studying the population of the involved 40S and 32S Rydberg states which is essential for the Rydberg blockade enabling the single-photon source concept. Severe broadening of the 40S state likely stemming from cell wall interaction is shown and spectrally narrow and time evolving features are characterized for the 32S state. The bulk of measured fluorescence stems from a three-photon Raman-type transition and, while a Rydberg blockade effect is found, no signal can conclusively be attributed to a populated Rydberg state.Chair: Tobias Schätz
14.10.25 – Adrian Kirchner, TU Graz
Adrian Kirchner:
Generating short pulses at MHz repetition rates: Tabletop coherent radiation sources from the UV to the NIR
Chair: Lukas Bruder
