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Intense Extreme Ultraviolet Pulses for Attosecond Pump-Probe Experiments

Plach, Marius LU (2025)
Abstract
Attosecond science enables the study of ultrafast dynamics on atomic scales, providing fundamental insights into light–matter interaction. This thesis work aims to advance the development and application of an attosecond light source capable of delivering extreme ultraviolet (XUV) pulses with exceptionally high intensity.

High-order harmonic generation (HHG) is a nonlinear process where a strong laser—typically in the infrared (IR) spectral region—is focused into a gas target, producing attosecond pulses in the XUV spectral region. These pulses are commonly used in pump-probe experiments, where a pump pulse excites the system and a probe pulse interrogates the induced dynamics, allowing for time-resolved measurements of ultrafast... (More)
Attosecond science enables the study of ultrafast dynamics on atomic scales, providing fundamental insights into light–matter interaction. This thesis work aims to advance the development and application of an attosecond light source capable of delivering extreme ultraviolet (XUV) pulses with exceptionally high intensity.

High-order harmonic generation (HHG) is a nonlinear process where a strong laser—typically in the infrared (IR) spectral region—is focused into a gas target, producing attosecond pulses in the XUV spectral region. These pulses are commonly used in pump-probe experiments, where a pump pulse excites the system and a probe pulse interrogates the induced dynamics, allowing for time-resolved measurements of ultrafast processes.

XUV–IR pump-probe schemes investigate electron dynamics via interactions that involve a single XUV and several infrared photons. However, infrared-driven processes can add complexity to the interpretation of the induced dynamics. In contrast, XUV–XUV pump-probe schemes provide a more direct approach, in which single-photon-induced dynamics are probed by a single second photon. Reaching the regime in which two XUV photons are absorbed requires high intensities, but the inherently low conversion efficiency of HHG poses a major challenge. To overcome this limitation, generation conditions, phase-matching conditions, and the wavefront characteristics of the driving field must be optimized.

This thesis demonstrates advancements in generating intense attosecond XUV pulses by optimizing the HHG process. Additionally, it explores how generation conditions affect the harmonic focus position and waist, influencing the ability to refocus the XUV pulses to a high-intensity spot. Beyond source optimization, applications of intense attosecond pulses in XUV–XUV and XUV–IR pump-probe experiments are investigated, enabling studies of electron dynamics upon photoionization. These experiments provide new insights into photoionization and ultrafast charge migration, enhancing our understanding of attosecond dynamics.

By refining attosecond pulse generation, this thesis contributes to the next generation of high-intensity ultrafast light sources, opening new possibilities for time-resolved studies in atomic and molecular physics. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Prof. Witte, Stefan, Delft University of Technology, The Netherlands.
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Attosecond Science, Ultrafast Science, High-Order Harmonic Generation, XUV Pulses, Photoionization Dynamics, Intense XUV Beamline
pages
205 pages
publisher
Department of Physics, Lund University
defense location
Lecture Hall Rydbergsalen, Department of Physics, Professorsgatan 1, Faculty of Engineering LTH, Lund University, Lund.
defense date
2025-03-28 13:15:00
ISBN
978-91-8104-396-9
978-91-8104-397-6
language
English
LU publication?
yes
id
4c6ee29d-0401-459c-8a77-408c9fb3ec65
date added to LUP
2025-03-03 17:51:49
date last changed
2025-04-04 14:58:09
@phdthesis{4c6ee29d-0401-459c-8a77-408c9fb3ec65,
  abstract     = {{Attosecond science enables the study of ultrafast dynamics on atomic scales, providing fundamental insights into light–matter interaction. This thesis work aims to advance the development and application of an attosecond light source capable of delivering extreme ultraviolet (XUV) pulses with exceptionally high intensity.<br/><br/>High-order harmonic generation (HHG) is a nonlinear process where a strong laser—typically in the infrared (IR) spectral region—is focused into a gas target, producing attosecond pulses in the XUV spectral region. These pulses are commonly used in pump-probe experiments, where a pump pulse excites the system and a probe pulse interrogates the induced dynamics, allowing for time-resolved measurements of ultrafast processes.<br/><br/>XUV–IR pump-probe schemes investigate electron dynamics via interactions that involve a single XUV and several infrared photons. However, infrared-driven processes can add complexity to the interpretation of the induced dynamics. In contrast, XUV–XUV pump-probe schemes provide a more direct approach, in which single-photon-induced dynamics are probed by a single second photon. Reaching the regime in which two XUV photons are absorbed requires high intensities, but the inherently low conversion efficiency of HHG poses a major challenge. To overcome this limitation, generation conditions, phase-matching conditions, and the wavefront characteristics of the driving field must be optimized.<br/><br/>This thesis demonstrates advancements in generating intense attosecond XUV pulses by optimizing the HHG process. Additionally, it explores how generation conditions affect the harmonic focus position and waist, influencing the ability to refocus the XUV pulses to a high-intensity spot. Beyond source optimization, applications of intense attosecond pulses in XUV–XUV and XUV–IR pump-probe experiments are investigated, enabling studies of electron dynamics upon photoionization. These experiments provide new insights into photoionization and ultrafast charge migration, enhancing our understanding of attosecond dynamics.<br/><br/>By refining attosecond pulse generation, this thesis contributes to the next generation of high-intensity ultrafast light sources, opening new possibilities for time-resolved studies in atomic and molecular physics.}},
  author       = {{Plach, Marius}},
  isbn         = {{978-91-8104-396-9}},
  keywords     = {{Attosecond Science; Ultrafast Science; High-Order Harmonic Generation; XUV Pulses; Photoionization Dynamics; Intense XUV Beamline}},
  language     = {{eng}},
  month        = {{03}},
  publisher    = {{Department of Physics, Lund University}},
  school       = {{Lund University}},
  title        = {{Intense Extreme Ultraviolet Pulses for Attosecond Pump-Probe Experiments}},
  url          = {{https://lup.lub.lu.se/search/files/209638599/Thesis_Marius_Plach_LUCRIS_B.pdf}},
  year         = {{2025}},
}