Attosecond pulse shaping at a seeded free-electron laser : : towards attosecond time-resolved experiments at the free-electron lasers

Abstract: Quantum mechanics governs the structure and dynamics of the microcosm. The advent of lasers led to the development of new tools to investigate quantum mechanics’ fundamental aspects using light-matter interactions. In particular, pulsed lasers made it possible to probe dynamics occurring in the microcosm, which opened up opportunities for measurement and control of the processes. Depending on the elements involved, dynamics takes place at a specific time scale. For instance, the vibration of atoms in molecules happens on a time scale ranging from a few tens to hundreds of femtoseconds, while the electron dynamics on the atomic scale occurs on a time scale of a few to hundreds of attoseconds. According to quantum mechanics, the time scale of a dynamical process depends on the energy difference of
the states involved. The investigation of electron dynamics in its natural time and length scales requires pulses of attosecond (as) duration with central wavelengths in the spectral range spanning from extreme ultraviolet (XUV) to X-rays.
Presently, the electron dynamics are investigated using the attosecond pulses generated via high harmonic generation (HHG). The attosecond pulses generated by the HHG process suffer from the intrinsically low conversion efficiency of the process and the absence of methods to independently control the amplitude and phase of the harmonics generated. The lack of such a method corresponds to difficulty in manipulating the pulse structure as per requirement. On the contrary, free-electron lasers (FELs) can generate XUV/X-ray pulses with unprecedented intensities and a few femtosecond duration, which limits the temporal resolution offered by these facilities for the time-resolved investigations.
The results presented in this work opens up the opportunities to perform attosecond time-resolved experiments at the FELs. Phase-locked harmonics from the seeded FEL FERMI are employed to generate the XUV attosecond pulse trains (APTs) with intensities much higher than that are routinely achieved by the HHG process. A novel two-color photoionization method named Correlation based reconstruction of attosecond pulses (CoBRA), inspired by the reconstruction of attosecond bursts by interference of two-photon transitions (RABBITT) technique, is developed and presented to characterize the generated APTs. The scheme of generating radiation at FEL FERMI permits independent control of the harmonics’ phases and amplitudes, allowing for a complex attosecond waveform shaping of the generated APTs. The results confirming the generation, characterization, and complex waveform shaping are discussed in the thesis together with a detailed analysis of the underlying theoretical model based on strong-field approximation, which is widely used in the attosecond community. The thesis also sheds light on few experiments foreseen to be conducted at FEL FERMI with attosecond temporal resolution

Angaben zum Objekt

• Standort: Deutsche Nationalbibliothek Frankfurt am Main
• Umfang: Online-Ressource
• Sprache: Englisch
• Anmerkungen: Universität Freiburg, Dissertation, 2021

Klassifikation und Themen

• Schlagwort: Pulse ; Free electron lasers ; Time

Beteiligte, Orts- und Zeitangaben

• Ereignis: Veröffentlichung
• (wo): Freiburg
• (wer): Universität
• (wann): 2021
• Urheber: Maroju, Praveen Kumar
• Beteiligte Personen und Organisationen: Sansone, Giuseppe ; Albert-Ludwigs-Universität Freiburg. Fakultät für Mathematik und Physik ; Attosekunden- und Starkfeldphysik

Weitere Informationen

• DOI: 10.6094/UNIFR/220018
• URN: urn:nbn:de:bsz:25-freidok-2200189
• Rechteinformation: Kein Open Access; Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Letzte Aktualisierung: 25.03.2025, 13:55 MEZ