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1.
Advantages and disadvantages of experiments with ultrashort two-color pulses
Matija Stupar, doktorska disertacija

Opis: Advances in the development of lasers have led to a new class of radiation sources generating coherent, tunable, ultrashort light pulses in the spectral region ranging from infrared to soft X-rays. This includes high-order harmonics generation in gas (HHG), on which relies the CITIUS facility at University of Nova Gorica (Slovenia), and free-electron lasers (FELs), such as the facility FERMI at Elettra-Sincrotrone Trieste (Italy). The distinctive structure of HHG and FEL radiation paved the way to time-resolved experiments, which are performed to investigate events occurring on a short, or very short, temporal scale, from picoseconds to femtoseconds. This work focuses on the advantages and disadvantages of some experimental techniques based on using these novel light sources to investigate the microscopic and/or ultrafast dynamics of matter samples, which have been previously driven out of equilibrium. Advantages rely on the implementation of various applications based on two-color schemes and, more specifically, include the possibility of acquiring two-dimensional frequency maps, measuring electrons’ effective masses, or investigating electronic properties decoupled from the influence of the lattice. Particular focus will be put on experimental methods relying on photoelectric effect and photoelectron spectroscopy. In all experiments, we took advantage of one or more specific properties of HHG and FEL sources, such as controllable chirp, to study laser dressed states in helium, variable polarization, to study electronic properties of iron-based pnictides and ultrashort pulses (< 10 fs) to study the purely electronic dynamics in transition metal dichalcogenides. On the other hand, the study of the interface between a molecule and a topological insulator revealed some intrinsic limitations and physical drawbacks of the technique, such as spurious effects originating from the high power pulses, like multiphoton absorption and the space charge effect, or the reduction of experimental resolution when pushing for shorter and shorter pulse durations. Some disadvantages are also connected to the current state-of-the-art in the field of ultrashort laser systems, where a trade-off needs to be found between repetition rate and laser power. Finally, state-of-the-art experiments based on the ability to generate ultrashort pulses carrying orbital angular momentum in visible, near-infrared as well as extreme UV range will be presented. The use of these pulses opens the door to the investigation of new physical phenomena, such as probing magnetic vortices using extreme ultraviolet light from a free-electron laser or imprinting the spatial distribution of an ultrashort infrared pulse carrying orbital angular momentum onto a photoelectron wave packet.
Najdeno v: ključnih besedah
Povzetek najdenega: ...at University of Nova Gorica (Slovenia), and free-electron lasers (FELs), such as the facility FERMI...
Ključne besede: ultrafast lasers, two-color experiments, photoemission, high-order harmonic generation, free-electron lasers, hot-electrons dynamics, surface science, pump-probe photoemission, ultraviolet photoemission, orbital angular momentum
Objavljeno: 02.12.2020; Ogledov: 5; Prenosov: 0
.pdf Polno besedilo (19,78 MB)

2.
Complete Characterization of Phase and Amplitude of Bichromatic Extreme Ultraviolet Light
Primož Rebernik Ribič, Giovanni De Ninno, 2019, izvirni znanstveni članek

Opis: Intense, mutually coherent beams of multiharmonic extreme ultraviolet light can now be created using seeded free-electron lasers, and the phase difference between harmonics can be tuned with attosecond accuracy. However, the absolute value of the phase is generally not determined. We present a method for determining precisely the absolute phase relationship of a fundamental wavelength and its second harmonic, as well as the amplitude ratio. Only a few easily calculated theoretical parameters are required in addition to the experimental data.
Najdeno v: ključnih besedah
Povzetek najdenega: ...light can now be created using seeded free-electron lasers, and the phase difference between harmonics...
Ključne besede: free-electron lasers, coherence, phase, attosecond
Objavljeno: 12.01.2020; Ogledov: 498; Prenosov: 0
.pdf Polno besedilo (293,60 KB)

3.
A detailed investigation of single-photon laser enabled Auger decay in neon
Primož Rebernik Ribič, Giovanni De Ninno, 2019, izvirni znanstveni članek

Opis: Single-photon laser enabled Auger decay (spLEAD) is an electronic de-excitation process which was recently predicted and observed in Ne. We have investigated it using bichromatic phase-locked free electron laser radiation and extensive angle-resolved photoelectron measurements, supported by a detailed theoretical model. We first used separately the fundamental wavelength resonant with the Ne+ 2s–2p transition, 46.17 nm, and its second harmonic, 23.08 nm, then their phase-locked bichromatic combination. In the latter case the phase difference between the two wavelengths was scanned, and interference effects were observed, confirming that the spLEAD process was occurring. The detailed theoretical model we developed qualitatively predicts all observations: branching ratios between the final Auger states, their amplitudes of oscillation as a function of phase, the phase lag between the oscillations of different final states, and partial cancellation of the oscillations under certain conditions.
Najdeno v: ključnih besedah
Povzetek najdenega: ...We have investigated it using bichromatic phase-locked free electron laser radiation and extensive angle-resolved photoelectron... ...laser enabled Auger decay (spLEAD) is an electronic de-excitation process which was recently predicted and... ...laser enabled Auger decay, free-electron lasers, neon...
Ključne besede: laser enabled Auger decay, free-electron lasers, neon
Objavljeno: 12.01.2020; Ogledov: 406; Prenosov: 0
.pdf Polno besedilo (996,35 KB)

4.
Shortening the pulse duration in seeded free-electron lasers by chirped microbunching
Primož Rebernik Ribič, Takashi Tanaka, 2019, izvirni znanstveni članek

Opis: In externally seeded free-electron lasers (FELs) that rely on a frequency upconversion scheme to generate intense short-wavelength light pulses, the slippage effect in the radiator imposes a lower limit on the FEL pulse duration, which is typically on the order of a few tens of femtoseconds. Recently it was proposed that a combination of a chirped microbunch and a tapered undulator can be used to break this limit. Although the method has the potential to reduce the FEL pulse duration down to a level that cannot be achieved by current state-of-the-art technology, it requires a very short seed pulse (∼ one optical cycle or less), making it challenging to put this concept into practical use. Here, we propose an alternative technique to relax the requirement on the seed pulse length. We show that the modified scheme allows generation of FEL pulses with durations much shorter than that determined by the seed pulse and the slippage effect. The performance of the method, which can easily be implemented at existing seeded FEL user facilities, is evaluated through a campaign of analytical calculations and simulations. For our set of typical seeded FEL parameters, we expect the generation of 1.6 fs long pulses at 26 nm with a peak power of 10 GW using a 20 fs long chirped seed pulse operating at 260 nm.
Najdeno v: ključnih besedah
Ključne besede: free-electron lasers, short pulses, femtosecond
Objavljeno: 12.01.2020; Ogledov: 438; Prenosov: 0
.pdf Polno besedilo (1,21 MB)

5.
Coherent THz Emission Enhanced by Coherent Synchrotron Radiation Wakefield
Primož Rebernik Ribič, Giovanni De Ninno, 2018, izvirni znanstveni članek

Opis: We demonstrate that emission of coherent transition radiation by a ∼1 GeV energy-electron beam passing through an Al foil is enhanced in intensity and extended in frequency spectral range, by the energy correlation established along the beam by coherent synchrotron radiation wakefield, in the presence of a proper electron optics in the beam delivery system. Analytical and numerical models, based on experimental electron beam parameters collected at the FERMI free electron laser (FEL), predict transition radiation with two intensity peaks at ∼0.3 THz and ∼1.5 THz, and extending up to 8.5 THz with intensity above 20 dB w.r.t. the main peak. Up to 80-µJ pulse energy integrated over the full bandwidth is expected at the source, and in agreement with experimental pulse energy measurements. By virtue of its implementation in an FEL beam dump line, this work promises dissemination of user-oriented multi-THz beamlines parasitic and self-synchronized to EUV and x-ray FELs.
Najdeno v: ključnih besedah
Povzetek najdenega: ...electron beam parameters collected at the FERMI free electron laser (FEL), predict transition radiation with... ...terahertz radiation, free-electron lasers, coherent transition radiation...
Ključne besede: terahertz radiation, free-electron lasers, coherent transition radiation
Objavljeno: 12.01.2020; Ogledov: 468; Prenosov: 0
.pdf Polno besedilo (1,62 MB)

6.
Chirped pulse amplification in an extreme-ultraviolet free-electron laser
David Gauthier, E. Allaria, Marcello Coreno, Ivan Cudin, Hugo Dacasa, Miltcho Bojanov Danailov, Alexander Demidovich, S. Di Mitri, B. Diviacco, Eugenio Ferrari, Primož Rebernik Ribič, Giovanni De Ninno, 2016, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...free-electron lasers, chirped pulse amplification, femtosecond...
Ključne besede: free-electron lasers, chirped pulse amplification, femtosecond
Objavljeno: 13.01.2020; Ogledov: 493; Prenosov: 2
Gradivo ima več datotek! Več...

7.
Generation and applications of extreme-ultraviolet vortices
Carlos Hernández-García, Jorge Vieira, Jose T. Mendonça, Laura Rego, Julio San Román, Luis Plaja, Primož Rebernik Ribič, David Gauthier, Antonio Picón, 2017, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...orbital angular momentum of photons, high-harmonic generation, free-electron lasers, plasma physics...
Ključne besede: XUV/X-ray vortices, orbital angular momentum of photons, high-harmonic generation, free-electron lasers, plasma physics
Objavljeno: 13.01.2020; Ogledov: 475; Prenosov: 1
Gradivo ima več datotek! Več...

8.
High resolution beam profiling of X-ray free electron laser radiation by polymer imprint development
Benedikt Rösner, Florian Döring, Primož Rebernik Ribič, David Gauthier, Emiliano Principi, Claudio Masciovecchio, Marco Zangrando, Joan Vila-Comamala, Giovanni De Ninno, Christian David, 2017, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...free-electron lasers, metrology, polymers, X-ray optics...
Ključne besede: free-electron lasers, metrology, polymers, X-ray optics
Objavljeno: 13.01.2020; Ogledov: 415; Prenosov: 0

9.
10.
Beyond the limits of 1D coherent synchrotron radiation
A. D. Brynes, P. Smorenburg, I. Akkermans, E. Allaria, Laura Badano, S. Brussaard, M. B. Danailov, Alexander Demidovich, Giovanni De Ninno, David Gauthier, Primož Rebernik Ribič, 2018, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...coherent synchrotron radiation, free electron lasers, accelerators...
Ključne besede: coherent synchrotron radiation, free electron lasers, accelerators
Objavljeno: 14.01.2020; Ogledov: 490; Prenosov: 2
Gradivo ima več datotek! Več...

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