High-order harmonic generation with few-cycle pulses for ultrafast electron spectroscopy
Ouahioune, Nedjma LU
(2026)
In Lund Reports on Atomic Physics, LRAP (2026)
- Abstract
- In this thesis, a high-repetition-rate attosecond light source based on high-order harmonic generation in gases was used to perform time-resolved electron spectroscopy in atoms and solids. The source was driven by few-cycle near-infrared laser pulses with a controllable carrier-to-envelope phase, enabling the generation of sequences of two to four attosecond pulses in the extreme ultraviolet range within only a few laser half-cycles. Part of the work was devoted to characterizing these short attosecond pulse trains using laser-assisted photoionization. The results reveal that both microscopic and macroscopic aspects of the generation process influence the number and relative intensity of the pulses contributing at different photon... (More)
- In this thesis, a high-repetition-rate attosecond light source based on high-order harmonic generation in gases was used to perform time-resolved electron spectroscopy in atoms and solids. The source was driven by few-cycle near-infrared laser pulses with a controllable carrier-to-envelope phase, enabling the generation of sequences of two to four attosecond pulses in the extreme ultraviolet range within only a few laser half-cycles. Part of the work was devoted to characterizing these short attosecond pulse trains using laser-assisted photoionization. The results reveal that both microscopic and macroscopic aspects of the generation process influence the number and relative intensity of the pulses contributing at different photon energies. Temporal confinement of the emission was observed and attributed to subcycle phase-matching dynamics. The duration of the attosecond pulse trains was further reduced through precise control of the time-dependent polarization of the driving laser field. Subcycle polarization gating, where linear polarization is confined near the peak of the pulse envelope, strongly reduced the attosecond pulse duration. This was experimentally evidenced by the presence of continuous spectra highly sensitive to the laser carrier-to-envelope phase.
Another part of this thesis studied the impact of effects arising from the ultrashort nature of the light fields on laser-assisted photoionization of helium, where interference between electron wavepackets plays a central role. Four new types of quantum interference involving one-photon ionization pathways through absorption of the attosecond pulses and two-photon ionization pathways involving the absorption or emission of an additional laser photon were observed and theoretically explained. A second study investigated interference effects involving highly excited states of helium, highlighting the influence of the spectral amplitude and phase of the laser field. A retrieval method was developed to extract information about the excited states and the light fields.
Finally, measurements of ultrafast electron dynamics in semiconductors were performed. Carrier relaxation dynamics in cubic tin(II) sulfide were investigated under various photoexcitation conditions using attosecond transient absorption spectroscopy. Several relaxation pathways could be disentangled, including the onset of many-body interactions between carriers, which were found to accelerate cooling and recombination processes from a threshold photoinduced carrier density. Using time-resolved photoemission electron microscopy, the potential for spatial localization of photoelectron emission from indium phosphide nanowires driven by the few-cycle laser pulses was also experimentally and theoretically investigated. The photoelectron kinetic-energy distributions were found to be compatible with sub-femtosecond emission durations. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/a5a80fb3-4113-46ba-988f-0dd14622f700
- author
- Ouahioune, Nedjma
LU
- supervisor
- opponent
-
- Dr. Lepine, Franck, CNRS-ILM Lyon, France.
- organization
- publishing date
- 2026-06-04
- type
- Thesis
- publication status
- published
- subject
- keywords
- High-order harmonic generation, Attosecond, Photoionization
- in
- Lund Reports on Atomic Physics, LRAP (2026)
- pages
- 201 pages
- publisher
- Department of Physics, Lund University
- defense location
- Lecture Hall Rydbergsalen, Department of Physics, Professorsgatan 1, Faculty of Engineering LTH, Lund University, Lund. The dissertation will be live streamed, but part of the premises is to be excluded from the live stream. Zoom: https://lu-se.zoom.us/j/63671564906?pwd=LaTI39PH8qdYeF3om2UdjF12tzBm9k.1
- defense date
- 2026-09-04 13:00:00
- ISSN
- 0281-2762
- 0281-2762
- ISBN
- 978-91-8104-985-5
- 978-91-8104-984-8
- language
- English
- LU publication?
- yes
- id
- a5a80fb3-4113-46ba-988f-0dd14622f700
- date added to LUP
- 2026-06-04 13:54:02
- date last changed
- 2026-06-09 13:10:54
@phdthesis{a5a80fb3-4113-46ba-988f-0dd14622f700,
abstract = {{In this thesis, a high-repetition-rate attosecond light source based on high-order harmonic generation in gases was used to perform time-resolved electron spectroscopy in atoms and solids. The source was driven by few-cycle near-infrared laser pulses with a controllable carrier-to-envelope phase, enabling the generation of sequences of two to four attosecond pulses in the extreme ultraviolet range within only a few laser half-cycles. Part of the work was devoted to characterizing these short attosecond pulse trains using laser-assisted photoionization. The results reveal that both microscopic and macroscopic aspects of the generation process influence the number and relative intensity of the pulses contributing at different photon energies. Temporal confinement of the emission was observed and attributed to subcycle phase-matching dynamics. The duration of the attosecond pulse trains was further reduced through precise control of the time-dependent polarization of the driving laser field. Subcycle polarization gating, where linear polarization is confined near the peak of the pulse envelope, strongly reduced the attosecond pulse duration. This was experimentally evidenced by the presence of continuous spectra highly sensitive to the laser carrier-to-envelope phase.<br/><br/>Another part of this thesis studied the impact of effects arising from the ultrashort nature of the light fields on laser-assisted photoionization of helium, where interference between electron wavepackets plays a central role. Four new types of quantum interference involving one-photon ionization pathways through absorption of the attosecond pulses and two-photon ionization pathways involving the absorption or emission of an additional laser photon were observed and theoretically explained. A second study investigated interference effects involving highly excited states of helium, highlighting the influence of the spectral amplitude and phase of the laser field. A retrieval method was developed to extract information about the excited states and the light fields. <br/><br/>Finally, measurements of ultrafast electron dynamics in semiconductors were performed. Carrier relaxation dynamics in cubic tin(II) sulfide were investigated under various photoexcitation conditions using attosecond transient absorption spectroscopy. Several relaxation pathways could be disentangled, including the onset of many-body interactions between carriers, which were found to accelerate cooling and recombination processes from a threshold photoinduced carrier density. Using time-resolved photoemission electron microscopy, the potential for spatial localization of photoelectron emission from indium phosphide nanowires driven by the few-cycle laser pulses was also experimentally and theoretically investigated. The photoelectron kinetic-energy distributions were found to be compatible with sub-femtosecond emission durations.}},
author = {{Ouahioune, Nedjma}},
isbn = {{978-91-8104-985-5}},
issn = {{0281-2762}},
keywords = {{High-order harmonic generation; Attosecond; Photoionization}},
language = {{eng}},
month = {{06}},
publisher = {{Department of Physics, Lund University}},
school = {{Lund University}},
series = {{Lund Reports on Atomic Physics, LRAP (2026)}},
title = {{High-order harmonic generation with few-cycle pulses for ultrafast electron spectroscopy}},
url = {{https://lup.lub.lu.se/search/files/252093680/e-nailing_ex_Nedjma.pdf}},
year = {{2026}},
}