Patrick Friebel

Max Planck Institute for Nuclear Physics

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Laura Cattaneo

Max Planck Institute for Nuclear Physics

Marta L. Murillo-Sánchez

Max Planck Institute for Nuclear Physics

C. Vozzi

Istituto di Fotonica e Nanotecnologie

Luise Becker

Philipps University of Marburg

Daria Ruth Galimberti

Radboud University Nijmegen

Andrea Annunziata

Istituto di Fotonica e Nanotecnologie

Davide Faccialá

Istituto di Fotonica e Nanotecnologie

Thomas Ding

Max Planck Institute for Nuclear Physics

S. Stagira

Politecnico di Milano

Alexander Magunia

Max Planck Institute for Nuclear Physics

Cooperative Institutions

Max Planck Institute for Nuclear Physics

Politecnico di Milano

Istituto di Fotonica e Nanotecnologie

National Research Council

Center for Biomolecular Nanotechnologies

Heidelberg University

Mylan (Switzerland)

Istituto Nazionale di Documentazione Innovazione e Ricerca Educativa

Radboud University Nijmegen

Istituto Nazionale per la Fisica della Materia

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Line-shape broadening of an autoionizing state in helium at high XUV intensity

New Journal of Physics (2021)

Lennart Aufleger Patrick Friebel Patrick Rupprecht Alexander Magunia Thomas Ding

Abstract We study the interaction of intense extreme ultraviolet (XUV) light with the 2s2p doubly excited state in helium. In addition to previously understood energy-level and phase shifts, high XUV intensities may lead to other absorption-line-shape distortions. Here, we report on experimental transient-absorption spectroscopy results on the 2s2p line-width modification in helium in intense stochastic XUV fields. A few-level-model simulation is realized to investigate the origins of this effect. We find that the line-shape broadening is connected to the strong coupling of the ground state to the 2s2p doubly excited state which is embedded in the ionization continuum. As the broadening takes place for intensities lower than for other strong-coupling processes, e.g. observed asymmetry changes of the absorption profile, this signature can be identified already in an intermediate intensity regime. These findings are in general relevant for resonant inner-shell transitions in nonlinear experiments with XUV and x-ray photon energies at high intensity.

Extreme ultraviolet

Line (geometry)

10.1088/1367-2630/ac3b2e

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Pulse length effects on autoionizing states under the influence of intense SASE XUV fields

Journal of Physics B Atomic Molecular and Optical Physics (2020)

Lennart Aufleger Patrick Friebel Patrick Rupprecht Alexander Magunia Thomas Ding

Abstract The Fano absorption line shape of an autoionizing state encodes information on its internal atomic structure and dynamics. When driven near-resonantly with intense extreme ultraviolet (XUV) electric fields, the absorption profile can be deliberately modified, including observable changes of both the line-shape asymmetry and strength of the resonance, revealing information on the underlying dynamics of the system in response to such external driving. We report on the influence of the XUV pulse parameters at high intensity that can be achieved with a free-electron laser (FEL) with statistically broadened spectra based on self-amplified spontaneous emission (SASE). More specifically, the impact of the FEL pulse duration is studied for the example of the doubly excited 2s2p resonance in helium, where line-shape modifications have been measured with XUV transient absorption spectroscopy in Fraunhofer-type transmission geometry. A computational few-level-model provides insight into the impact of different average pulse durations of the stochastic FEL pulses. These findings are supported by measurements performed at the Free-Electron Laser in Hamburg (FLASH) and provide further insight into XUV strong-coupling dynamics of resonant transitions driven by intense high-frequency FEL sources.

Extreme ultraviolet

Pulse duration

Line (geometry)

10.1088/1361-6455/abbe2d

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Liquid crystal-based temperature-controlled recirculating flat jet system

Review of Scientific Instruments (2024)

Marta L. Murillo-Sánchez Natalia Copete-Plazas Elias Bürkle Patrick Friebel Laura Cattaneo

In this paper, the design and implementation of a temperature-controlled recirculating flat jet system for liquid crystals (LCs)-based experiments are presented. In these experiments, the target liquid is usually exposed to medium to high laser fluences, possibly resonant with specific excitation, thus resulting in a change of local temperature and sudden degradation. To overcome this problem, each laser pulse must interact with a new volume of liquid, preferably with flat surfaces, while avoiding the use of substrates. A well-established solution consists of impinging two identical laminar jets that force the liquid into a radial expansion perpendicular to the plane formed by the jets, resulting in a consecutive chain of flat sheets bound by thick rims. In this context, LCs pose several challenges considering their viscosity, non-Newtonian behavior, and mesophase nature. Here, a precise control of temperature, thus mesophase, and pressure is demonstrated enabling the use of LCs in an impinging jet system. In particular, the system presented here delivers stable fluid chains of different sizes and thicknesses. The viscosity and non-Newtonian behavior of the LCs have a significant impact on the thickness of the chains as a function of the nozzle inner diameter, impinging angle, and radial distance from the impinging point. The flow rate, on the other hand, primarily affects the width and length of the liquid sheet.

10.1063/5.0210575

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Unveiling Low THz Dynamics of Liquid Crystals: Identification of Intermolecular Interaction among Intramolecular Modes

The Journal of Physical Chemistry B (2024)

Patrick Friebel Daria Ruth Galimberti Matteo Savoini Laura Cattaneo

Liquid crystals have found a wide area of application over the last few decades, proving to be excellent materials for tunable optics from visible to near-infrared frequencies. Currently, much effort is devoted to demonstrating their applicability at THz frequencies (1-10 THz), where tremendous advances of broadband and intense sources have been achieved. Yet, a detailed understanding of THz-triggered dynamics in liquid crystals is incomplete. Here, we perform broadband THz time domain spectroscopy on 4-cyano-4'-alkyl-biphenyl (

Trimer

10.1021/acs.jpcb.3c07947

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THz spectroscopy of thermotropic liquid crystals

Patrick Friebel Daria Ruth Galimberti Riccardo Piccoli Laura Cattaneo

We use few-cycle THz pulses to perform time-domain spectroscopy measurements of 8CB Liquid Crystal (LC). The measured absorption spectra for uniformly AC-aligned samples clearly indicate activity in the THz region: a set of strong bands above 4 THz followed by a broad plateau below are observed. DFT gas-phase calculations have been performed to assign the vibrational bands and to support the understanding of the observed features.

Thermotropic crystal

Crystal (programming language)

10.1117/12.2646581

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Liquid crystal wave plate operating close to 18 THz

Optics Letters (2024)

Fabio Novelli Patrick Friebel Marta L. Murillo-Sánchez J. Michael Klopf Laura Cattaneo

Controlling the properties of mid- and far-infrared radiation can provide a means to transiently alter the properties of materials for novel applications. However, a limited number of optical elements are available to control its polarization state. Here we show that a 15-µm thick liquid crystal cell containing 8CB (4-octyl-4'-cyanobiphenyl) in the ordered, smectic A phase can be used as a phase retarder or wave plate. This was tested using the bright, short-pulsed (∼1 ps) radiation centered at 16.5 µm (18.15 THz) that is emitted by a free electron laser at high repetition rate (13 MHz). These results demonstrate a possible tool for the exploration of the mid- and far-infrared range and could be used to develop novel metamaterials or extend multidimensional spectroscopy to this portion of the electromagnetic spectrum.

Waveplate

10.1364/ol.519177

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High-order Harmonic Generation in Thermotropic Liquid Crystals

arXiv (Cornell University) (2023)

Andrea Annunziata Luise Becker Marta L. Murillo-Sánchez Patrick Friebel S. Stagira

Thermotropic liquid crystals are versatile optical materials that exhibit a state of matter intermediate between liquids and solids. Their properties can change significantly with temperature, pressure, or other external factors, leading to different phases. The transport properties within these materials in different phases are still largely unexplored and their understanding would enable exciting prospects for innovative technological advancements. High-order harmonic spectroscopy proved to be a powerful spectroscopic tool for investigating the electronic and nuclear dynamics in matter. Here we report the first experimental observation of high-order harmonic generation in thermotropic liquid crystals in two different phase states, nematic and isotropic. We found the harmonic emission in the nematic phase to be strongly dependent on the relative orientation of the driving field polarization with respect to the liquid crystal alignment. Specifically, the harmonic yield has a maximum when the molecules are aligned perpendicularly to the polarization of the incoming radiation. Our results establish the first step for applying high-order harmonic spectroscopy as a tool for resolving ultrafast electron dynamics in liquid crystals with unprecedented temporal and spatial resolution.

Thermotropic crystal

10.48550/arxiv.2311.10211

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Unveiling low THz Dynamics of Liquid Crystals: Identification of Intermolecular Interaction among Intramolecular Modes

arXiv (Cornell University) (2023)

Patrick Friebel Daria Ruth Galimberti Matteo Savoini Laura Cattaneo

Liquid crystal based technologies have found considerably diversified uses and areas of application over the last few decades, proving to be excellent materials for tunable optical elements from visible to near-infrared frequencies. Currently, much effort is devoted to demonstrating their applicability in the far-infrared or THz spectral frequency (1 - 10 THz), where tremendous advances have been achieved in terms of broadband and intense sources. Yet a detailed understanding of the dynamics triggered by THz light in liquid crystals is far from complete. In this work, we perform broadband THz Time Domain Spectroscopy on the low-frequency modes of 4-cyano-4'-alkylbiphenyl (nCB) and 5-phenylcyclohexanes (PCH5) across different mesophases. DFT calculations on isolated molecules capture the majority of the measured response above 3 THz. In particular, the pronounced modes around 4.5 and 5.5 THz mainly originate from in-plane and out-of-plane bending of the cyano group. In contrast, the broad response below 3 THz, linked to modes of the alkyl chain, disagrees with the single molecule calculation. Here, we identify a clear intermolecular character of the response, supported by dimer and trimer calculations.

Trimer

10.48550/arxiv.2310.15567

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Liquid Crystals Meet Strong-Field Physics: First Attempts of HHG in Soft Matter

Luise Becker Andrea Annunziata Patrick Friebel Davide Faccialá C. Vozzi

We present preliminary results of HHG spectroscopy in 8CB smectic A liquid crystal under different geometries and temperature, using a single colour pumping scheme in the mid-IR wavelength with subsequent detection in the NIR-visible range.

Soft matter

10.1109/cleo/europe-eqec57999.2023.10232400

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High-order harmonic generation in liquid crystals

APL Photonics (2024)

Andrea Annunziata Luise Becker Marta L. Murillo-Sánchez Patrick Friebel S. Stagira

Thermotropic liquid crystals are versatile optical materials that exhibit a state of matter intermediate between liquids and solids. Their properties can change significantly with temperature, pressure, or other external factors, leading to different phases. The transport properties within these materials in different phases are still largely unexplored, and their understanding would enable exciting prospects for innovative technological advancements. High-order harmonic spectroscopy proved to be a powerful spectroscopic tool for investigating the electronic and nuclear dynamics in matter. Here, we report the first experimental observation of high-order harmonic generation in thermotropic liquid crystals in two different phase states, nematic and isotropic. We found the harmonic emission in the nematic phase to be strongly dependent on the relative orientation of the driving field polarization with respect to the liquid crystal alignment. Specifically, the harmonic yield has a maximum when the molecules are aligned perpendicularly to the polarization of the incoming radiation. Our results establish the first step for applying high-order harmonic spectroscopy as a tool for resolving ultrafast electron dynamics in liquid crystals with unprecedented temporal and spatial resolution.

Thermotropic crystal

10.1063/5.0191184

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Citations (1)