09.04.24 – Diego Porras Torre, Madrid, Spain

16.04.24 – Lotar Kurti & Maziyar Kazemi, Freiburg

23.04.24 – Marvin Schmoll, Freiburg

30.04.24 – Cristian Manzoni, IFN-CNR, Milano, Italy

07.05.24 – Jackson Ang’ong’a, Tübingen

14.05.24 – Chiara Lindner, Freiburg

28.05.24 – Franck Lepine, Lyon, France

04.06.24 – Jeremy Rouxel, Argonne National Laboratory

18.06.24 – Wentao Chen & Ferdinand Bergmeier, Freiburg

02.07.24 – Maxim Gelin, Hangzhou Dianzi University, China

09.07.24 – Paris Tzallas, Heraklion, Greece

28.05.24 – Franck Lepine, CNRS, Institut Lumière Matière, Lyon, France

Dynamics in complex (bio-)molecules induced by XUV Attosecond pulse excitation

Attosecond technology and High harmonic generation (HHG)-based light sources have had a major impact in photo-science as they combine the possibility to deliver high energy photons (VUV-XUV-soft X-ray), usually accessible at large scale facilities, with short pulse duration that allows to perform experiments with high time resolution (down to attosecond). Over the past years, we have developed experiments where HHG sources allowed us to track the ultrafast dynamics induced in complex molecules following an XUV excitation. In excited polycyclic aromatic hydrocarbons and diamontoid, we observed how the deposited energy is spread in strongly correlated electronic and vibrational degrees of freedom on femtosecond timescale. Here, we present recent experiments in which we study quantum electron scattering of the photoionized electron in large 2D and 3D molecules. We show that information on the spatial distribution of the hole is imprinted in the measured attosecond delay. Such experiments are also performed in biomolecules. While current attosecond experiments are essentially dedicated to „small“ neutral model molecules, we have recently pioneered the development of combined HHG and analytical chemistry technologies to perform time-resolved experiments in complex molecular ions as large as a protein using HHG light sources, providing information on the first steps following the interaction between ionizing radiation and biomolecules. These experiments demonstrate the possibility to perform experiments in complex biopolymers with attosecond precision and therefore pave the way to multiple time scales understanding of ionization induced processes in complex biomolecules.

Chair: Giuseppe Sansone

14.05.24 – Chiara Lindner, IPM Fraunhofer, Freiburg

Fourier-Transform Infrared Spectroscopy with Visible Light

Infrared spectroscopy is a widely used method for studying and identifying chemical compounds, as molecules absorb light at frequencies characteristic for their structure. A limiting factor, however, are infrared detectors, which are often slower, more expensive, and noisier than detectors for the visible spectral range.

In my research, I work on concepts for high-resolution infrared spectroscopy using visible light detection – based on quantum interference effects of correlated photons. Nonlinear interferometers based on spontaneous parametric down-conversion (SPDC) allow to measure the infrared transmission of a sample by only detecting visible light.

Transforming such a quantum optical experiment into a practical spectrometer poses challenges. In my research, I have found that the spectral information can be read-out in a manner similar to classical Fourier-transform spectroscopy. Based on this concept we were able to demonstrate broadband infrared spectroscopy with high spectral resolution. While technological advancements are a key step towards applications, this concept also illustrates the fundamental relations between indistinguishability, coherence, and spectral composition.

My talk will discuss measurements with correlated photons based on induced coherence and showcase the potential of the Fourier-transform approach and the developments towards improved infrared sensing.

Chair: Giuseppe Sansone

07.05.24 – Jackson Ang’ong’a, University of Tuebingen

A Cryogenic Strontium Quantum Processor

Current quantum computing platforms require hundreds of thousands to millions of physical qubits to perform practical computations. However, scaling up is technically challenging due to the difficulty in reliably addressing a large number of qubits. In our project, we plan to implement a quantum processor using well-isolated nuclear spin states of fermionic strontium-87 atoms trapped in optical tweezers arrays.

To achieve a large number of stable and well-controlled nuclear qubits, we will prepare these atoms in a 4K cryogenic chamber. This will enable long trap lifetimes, reduced decoherence from black-body radiation, and the use of superconducting coils to define stable nuclear qubits. I will discuss the progress made towards this goal and outline future objectives beyond the realization of the cryogenic strontium quantum processor.

Chair: Andreas Buchleitner

30.04.24 – Cristian Manzoni, IFN-CNR, Milano, Italy

A High-throughput multimodal wide-field Fourier-transform Raman microscope

Raman microscopy is a powerful analytical technique for materials and life sciences that enables mapping the spatial distribution of the chemical composition of a sample. State-of-the-art Raman microscopes, based on point-scanning frequency-domain detection, have long (∼1 s) pixel dwell times, making it challenging to acquire images of a significant area (e.g., 100 × 100 μm).

In this talk we will present an innovative compact wide-field Raman microscope based on a time-domain Fourier-transform approach, entirely developed at CNR and Politecnico di Milano (Italy). The novel system enables parallel acquisition of the Raman spectra on all pixels of a 2D detector. To this aim, we developed a common-path birefringent interferometer, which provides exceptional delay stability and reproducibility, and can rapidly acquire Raman maps (∼30 min for a 250 000 pixel image) with high spatial (<1 μm) and spectral (∼23 cm−1 ) resolutions.

We will explore how time-domain detection offers the unique advantage of disentangling fluorescence and Raman signals, which can both be measured separately. We validate the system by Raman imaging plastic microbeads and demonstrate its multimodal operation by capturing fluorescence and Raman maps of a multilayer-WSe2 sample (See Fig. 1), providing complementary information on the strain and number of layers of the material.

Figure 1: Florescence and Raman image of WSe2. (a) False-color RGB image obtained from the fluorescence map. Three circles indicate three selected regions of interest (ROIs) on 1-layer (1L, green and red) and 2-layer (2L, blue) WSe2. (b) Fluorescence spectra of selected ROIs in (a). (c) Peak map of the A1g Raman mode. Two circles indicate one ROI on 1L (red) and one ROI on 2L (blue). (d) Raman spectra of selected ROIs in (c). The inset shows a zoom of the peak.

Chair: Lukas Bruder

23.04.24 – Marvin Schmoll, Freiburg

Two-color high order harmonic generation

High order harmonic generation (HHG) using infrared driving fields has become a staple of experimental physics as it enables the creation of trains of attosecond pulses in the extreme ultraviolet (XUV) spectral region. Incorporating a weak second harmonic into the generation process has shown promise in enhancing harmonic yield and extending available frequencies, which is why this configuration is increasingly being explored. This talk presents the process of two-color HHG studied at two different setups both utilizing a Yb:KGW laser as light source.
In the first setup, a Mach-Zehnder-like interferometric arrangement, enhanced by Spatial Light Modulators (SLMs) in each arm, was employed. An active phase stabilization system running at 20 Hz was developed using the SLMs, achieving a delay stability of 0.2 rad. This stability proved enough to verify the dependence of harmonic yield on the relative phase between fundamental and second harmonic.
The second setup was built in collinear geometry presenting excellent passive delay stability. With its help, the yield oscillations could be studied further and a dependence of their phase on the harmonic order was uncovered. This beamline also includes a collinear delay line for XUV-pump IR-probe photoelectron spectroscopy in atomic and molecular targets at 50 kHz repetition rate. Said beamline was used for first test measurements in Argon. Clear delay dependent oscillations with the period of the IR field could be observed, opening the possibility for studies in more complicated targets.

Chair: Barbara Merzuk (AG Sansone)

16.04.24 – Lotar Kurti & Maziyar Kazemi, Freiburg

Time: 4:30 pm // Place: Lecture Hall 2

Lotar Kurti

A study of juniper berries from different areas of Albania by Infrared Spectroscopy

Oil extracted from different types of Juniper berries were studied using a Fourier-Transform Infrared Spectrometer (FTIR, NICOLET 6700). To obtain the juniper oil we have used the Clevenger method. The FTIR spectra show several characteristic absorptions, for example at about 2900 cm-1 as well as at 1460 cm-1 and 1380 cm-1, which will be discussed. It was found that while the oil composition is quite the same in juniper Communis (black) and juniper Oxycedrus (red), the concentration of the main compounds in red juniper is 20 times smaller than in the black one.

Chair: Bernd von Issendorff

Maziyar Kazemi

Synthesis and investigation of electrochemical properties of nanostructured BiVO4-WO3 thin films.

In recent years, because of global warming caused by CO2 emission, many approaches have been developed to replace fossil fuels. Photoelectrochemical (PEC) hydrogen production through water splitting, as invented by Fujishima in 1972, is one of the most promising methods. Since then, numerous materials, such as ZnO, TiO2, CdS, Fe2O3, have been investigated as photocatalyst candidates for hydrogen production. Among these compounds, Bi-based materials have attracted a lot of attention recently due to their small band gap. We have developed a new technique with the potential to prepare BiVO4 thin films with high stability, excellent uniformity, and adhesion on a large scale in an economical manner. Namely we have introduced a hot-spin coating technique (HSC) and optimized its parameters systematically. 

Chair: Bernd von Issendorff

09.04.24 – Diego Porras Torre, Institute of Theoretical Physics, CSIC, Madrid, Spain

Time: 4:30 pm // Place: Lecture Hall 2

Trapped ion quantum simulators

Trapped ion chains are ideal quantum systems to engineer effective particle-particle interactions and prepare complex quantum states. I will show how to use basic tools from atomic physics to induce spin-phonon couplings that induce quantum magnetic phases. I will also show the analogy between vibrational modes in trapped ions and photonic modes in waveguides. By using this analogy one can induce exciting quantum phenomena in the motion of ions, including topological and amplification effects.

Chair: Tobias Schaetz