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11.
Pulse duration of seeded free-electron lasers
Paola Finetti, Hauke Höppner, Enrico Allaria, Carlo Callegari, Flavio Capotondi, Paolo Cinquegrana, Marcello Coreno, Riccardo Cucini, Miltcho Bojanov Danailov, Alexander Demidovich, Giovanni De Ninno, Primož Rebernik Ribič, 2017, original scientific article

Found in: ključnih besedah
Summary of found: ...free-electron lasers, harmonic generation, pulse duration...
Keywords: free-electron lasers, harmonic generation, pulse duration
Published: 14.01.2020; Views: 1918; Downloads: 6
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12.
Echo-enabled harmonic generation lasing of the FERMI FEL in the soft X-ray spectral region
Primož Rebernik Ribič, 2019, published scientific conference contribution (invited lecture)

Found in: ključnih besedah
Keywords: free-electron lasers, harmonic generation, seeding
Published: 15.01.2020; Views: 1648; Downloads: 8
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13.
14.
Energy spread impact on HGHG and EEHG FEL pulse energy
Simone Spampinati, Enrico Allaria, Luca Giannessi, Primož Rebernik Ribič, 2019, published scientific conference contribution

Found in: ključnih besedah
Summary of found: ...free-electron lasers, harmonic generation...
Keywords: free-electron lasers, harmonic generation
Published: 15.01.2020; Views: 1929; Downloads: 63
URL Fulltext (0,00 KB)
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15.
Status and perspectives of the FERMI FEL facility (2019)
Luca Giannessi, Enrico Allaria, Laura Badano, S. Bassanese, Filippo Bencivenga, Carlo Callegari, Flavio Capotondi, Davide Castronovo, F. Cilento, Paolo Cinquegrana, Giovanni De Ninno, Primož Rebernik Ribič, 2019, published scientific conference contribution

Found in: ključnih besedah
Summary of found: ...free-electron lasers, harmonic generation...
Keywords: free-electron lasers, harmonic generation
Published: 15.01.2020; Views: 1884; Downloads: 66
URL Fulltext (0,00 KB)
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16.
Ultrafast Element-Specific Demagnetization in Alloys
Jurij Urbančič, doctoral dissertation

Abstract: The study of magnetism has long been an active area of interest for the scientific research, while also providing vast technological applications such as information storage. It was first observed in the middle of the 90s that irradiating a ferromagnetic material with an intense femtosecond laser pulse can result in a loss of magnetization occurring below one picosecond. Since then, the study of magnetism on these femtosecond timescales has been a field of growing interest, addressing the question of how fast can the magnetization modification occurs and what presents the fundamental limit of this speed. For the understanding of these experimental observations, a number of different models were proposed, although the responsible microscopic mechanisms are still under discussion. According to one group of models, the change in magnetic moment is due to the spin-flip mechanism occurring during scattering events between electrons and (quasi-)particles. An example of this is the so-called Microscopic Three-Temperature Model (M3TM). A different approach is employed by the Superdiffusive Spin Current Model, where the loss of magnetization is attributed to a flow of chargeless spin particles taking place after the laser excitation. With the purpose to explore the magnetic characteristic of materials, a range of investigation methods has been developed. One of them relies on the exploitation of the Magneto-Optical Kerr Effect (MOKE) and an incorporation of femtosecond laser pulses in pump-probe configuration. In this way, part of the beam from the same laser system is used to optically excite the system (the pump), while another part takes a snapshot of it (the probe), thus allowing us to investigate the magnetization dynamics with a femtosecond temporal resolution. In the experimental part of the thesis, we apply this MOKE technique to explore the demagnetization dynamics of a ferromagnetic alloy consisting of iron and nickel, also called Permalloy. It is observed that the magnetization is suppressed (quenched) in the first few hundred femtoseconds. Part of the experiments were performed using visible light with different fluences of the pump. The most notable observation is that this alloy exhibits different demagnetization dynamics at lower and higher fluence. What we see is a transition from one-step (demagnetization followed by a recovery on a much longer timescale) to a two-step (demagnetization followed by another slower demagnetization step) magnetization process occurring with the increment of pump fluence. This behavior is predicted and reproduced by the M3TM, which is applied for a comparison between experiments and theory.
Found in: ključnih besedah
Summary of found: ...High Harmonic Generation, Magnetism, Ultrafast, Materials...
Keywords: High Harmonic Generation, Magnetism, Ultrafast, Materials
Published: 08.05.2020; Views: 1969; Downloads: 0
.pdf Fulltext (12,06 MB)

17.
Towards ultrafast X-ray condensed matter physics with MHz repetition rate HHG sources
Jurij Urbančič, 2015, published scientific conference contribution abstract

Abstract: In recent years, an increasing number of ultrafast material science experiments are based on the use of table-top high-harmonic generation (HHG) lightsources [1,2]. Despite the huge success of these first experiments, a major drawback has been the limited repetition rate of these lightsources, in particular with respect to all types of photoemission experiments. Here, we combine newly developed high-repetition rate HHG sources [3,4] with state-of-the-art element-specific magneto-optical Kerr experiments. The chances and prospects for future ultrafast materials science experiments with these lightsources will be discussed.
Found in: ključnih besedah
Summary of found: ...are based on the use of table-top high- harmonic generation (HHG) lightsources [1,2]. Despite the huge...
Keywords: High Harmonic Generation, X-Rays, Condensed Matter
Published: 22.05.2020; Views: 1824; Downloads: 0

18.
The role of non-equilibrium dynamics in photo-induced phase transitions of correlated materials
Jurij Urbančič, 2015, published scientific conference contribution abstract

Abstract: We use femtosecond extreme-ultraviolet time- and angle-resolved photoelectron spectroscopy to study the ultrafast photo-induced suppression of the charge-density wave (CDW) in 1T-TiSe2. In the following non-equilibrium electron dynamics after femtosecond laser excitation, we see that hot-carrier multiplication is the primary driver for the ultrafast CDW suppression. As soon as the optically excited carriers have relaxed to a quasi-equilibrium hot Fermi-distribution electron gas, the CDW suppression stops. Theoretical calculations of the hot-carrier scattering processes and the screening properties further link the carrier multiplication to the observed CDW gap dynamics.
Found in: ključnih besedah
Summary of found: ...Correlated Materials, High Harmonic Generation, ARPES...
Keywords: Correlated Materials, High Harmonic Generation, ARPES
Published: 22.05.2020; Views: 1720; Downloads: 0

19.
Element-resolved study on the influence of a magnetic dopant on the exchange interaction in FePt on ultrashort timescales
Jurij Urbančič, 2017, published scientific conference contribution abstract

Abstract: In this study, we investigate the optically induced ultrafast demagnetization dynamics of a FePt alloy doped with Mn atoms on the characteristic timescale of the exchange interaction of a few femtoseconds. We use high harmonic generation with photon energies in the XUV to gain elemental resolution in a femtosecond magneto-optical Kerr-effect experiment [1] in transversal geometry. Following up on earlier experiments, which showed the importance of the exchange interaction in the demagnetization process in alloys [2,3], we see clear differences in the dynamical responses of the three elements Fe, Pt, and Mn. Our results suggest, that the exchange coupling between the magnetic moments of the FePt alloy and the Mn dopant changes on ultrashort timescales.
Found in: ključnih besedah
Summary of found: ...of a few femtoseconds. We use high harmonic generation with photon energies in the XUV...
Keywords: FePt, High Harmonic Generation, Laser, Magnetic Materials
Published: 22.05.2020; Views: 1845; Downloads: 0

20.
Spectrotemporal control of soft x-ray laser pulses
Najmeh S. Miria, Enrico Allaria, Niky Bruchon, Paolo Cinquegrana, Miltcho Bojanov Danailov, Giovanni De Ninno, S. Di Mitri, Eugenio Ferrari, Luca Giannessi, Primož Rebernik Ribič, 2020, original scientific article

Found in: ključnih besedah
Summary of found: ...coherent control, free electron lasers, echo-enabled harmonic generation...
Keywords: coherent control, free electron lasers, echo-enabled harmonic generation
Published: 15.06.2020; Views: 1712; Downloads: 54
URL Fulltext (0,00 KB)

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