| 1. |
- Jusko, Christoph, et al.
(författare)
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Spatio-temporal characterization of a femtosecond filament along its length
- 2020
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Ingår i: High Intensity Lasers and High Field Phenomena, HILAS 2020. - 9781557528209
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Konferensbidrag (refereegranskat)abstract
- We present an experimental method capable of characterizing spatio-temporal dynamics of a femtosecond filament v ia F ourier t ransform i nterferometry, p roviding a three-dimensional reconstruction of the driving pulse, while scanning along the entire length of the filament.
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| 2. |
- Louisy, Maïté, et al.
(författare)
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Compact single-shot d-scan setup for the characterization of few-cycle laser pulses
- 2017
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Ingår i: Applied Optics. - 1559-128X. ; 56:32, s. 9084-9089
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Tidskriftsartikel (refereegranskat)abstract
- We present a compact implementation of the ultrashort pulse measurement technique based on dispersion scans (d-scan), allowing single-shot measurement of few-cycle pulses. The main novelty in our design, making our setup extremely compact and simple, is the use, after a prism, of a spherical mirror in an off-axis geometry. The intentionally introduced strong astigmatism makes it possible to image the output of the crystal in one direction while focusing it in the other direction, resulting in the output face of the prism being imaged into a line in the second-harmonic crystal. The technique is validated by comparing measured dispersion scans, retrieved spectral phases and temporal profiles of this single-shot system with standard d-scan results.
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| 3. |
- Luo, Sizuo, et al.
(författare)
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Ultra-stable and versatile high-energy resolution setup for attosecond photoelectron spectroscopy
- 2023
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Ingår i: Advances in Physics: X. - 2374-6149. ; 8:1
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Forskningsöversikt (refereegranskat)abstract
- Attosecond photoelectron spectroscopy has opened up for studying light–matter interaction on ultrafast time scales. It is often performed with interferometric experimental setups that require outstanding stability. We demonstrate and characterize in detail an actively stabilized, versatile, high spectral resolution attosecond beamline based on a Mach-Zehnder interferometer. The active stabilization keeps the interferometer ultra-stable for several hours with an RMS stability of 13 as and a total pump-probe delay scanning range of (Formula presented.) fs. A tunable femtosecond laser source to drive high-order harmonic generation allows for precisely addressing atomic and molecular resonances. Furthermore, the interferometer includes a spectral shaper in 4f-geometry in the probe arm as well as a tunable bandpass filter in the pump arm, which offer additional high flexibility in terms of tunability as well as narrowband or polychromatic probe pulses. We demonstrate the capabilities of the beamline via experiments using several variants of the RABBIT (reconstruction of attosecond beating by two photon transitions) technique. In this setup, the temporal-spectral resolution of photoelectron spectroscopy can reach a new level of accuracy and precision.
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| 4. |
- Miranda, Miguel, et al.
(författare)
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All-optical measurement of the complete waveform of octave-spanning ultrashort light pulses
- 2019
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Ingår i: Optics Letters. - 0146-9592. ; 44:2, s. 191-194
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate the complete temporal characterization of the optical waveform of visible near-infrared octave-spanning ultrashort laser pulses, using an all-optical, all-solid-state, and fully inline dispersion-scan device based only on second-harmonic generation.
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| 5. |
- Miranda, Miguel, et al.
(författare)
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Fast iterative retrieval algorithm for ultrashort pulse characterization using dispersion scans
- 2017
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Ingår i: Journal of the Optical Society of America B: Optical Physics. - 0740-3224. ; 34:1, s. 190-197
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Tidskriftsartikel (refereegranskat)abstract
- We present an iterative retrieval algorithm based on data constraint for ultrashort pulse characterization using dispersion scan (d-scan). The proposed algorithm is much faster and leads to a drastic reduction of retrieval times, but, compared to the standard algorithm, it performs less robustly in the retrieval of noisy d-scan traces. The algorithm is tested on several simulated cases and in two different experimental cases in the few-cycle regime.
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| 6. |
- Nandi, Saikat, et al.
(författare)
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Observation of Rabi dynamics with a short-wavelength free-electron laser
- 2022
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 608:7923
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Tidskriftsartikel (refereegranskat)abstract
- Rabi oscillations are periodic modulations of populations in two-level systems interacting with a time-varying field(1). They are ubiquitous in physics with applications in different areas such as photonics(2), nano-electronics(3), electron microscopy(4) and quantum information(5). While the theory developed by Rabi was intended for fermions in gyrating magnetic fields, Autler and Townes realized that it could also be used to describe coherent light-matter interactions within the rotating-wave approximation(6). Although intense nanometre-wavelength light sources have been available for more than a decade(7-9), Rabi dynamics at such short wavelengths has not been directly observed. Here we show that femtosecond extreme-ultraviolet pulses from a seeded free-electron laser(10) can drive Rabi dynamics between the ground state and an excited state in helium atoms. The measured photoelectron signal reveals an Autler-Townes doublet and an avoided crossing, phenomena that are both fundamental to coherent atom-field interactions(11). Using an analytical model derived from perturbation theory on top of the Rabi model, we find that the ultrafast build-up of the doublet structure carries the signature of a quantum interference effect between resonant and non-resonant photoionization pathways. Given the recent availability of intense attosecond(12) and few-femtosecond(13) extreme-ultraviolet pulses, our results unfold opportunities to carry out ultrafast manipulation of coherent processes at short wavelengths using free-electron lasers.
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| 7. |
- Nandi, Saikat, et al.
(författare)
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Unraveling Rabi dynamics with a seeded FEL at XUV wavelength
- 2023
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Ingår i: 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023. - 9798350345995
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Konferensbidrag (refereegranskat)abstract
- Rabi oscillations, a prominent feature of coherent light-matter interaction arise when a two-level system interacts periodically with an external electromagnetic field [1]. Despite being a cornerstone in quantum physics, they are usually studied in the long-wavelength region, ranging from mid-infrared to visible. Here, we demonstrate that intense femtosecond extreme-ultraviolet (XUV) pulses from FERMI seeded free-electron laser [2] can drive Rabi oscillations between the two levels: 1s2 and 1s4p in helium.
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| 8. |
- Nayak, Arjun, et al.
(författare)
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Saddle point approaches in strong field physics and generation of attosecond pulses
- 2019
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Ingår i: Physics Reports. - : Elsevier BV. - 0370-1573. ; 833, s. 1-52
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Forskningsöversikt (refereegranskat)abstract
- Attoscience is the emerging field that accesses the fastest electronic processes occurring at the atomic and molecular length scales with attosecond (1 as = 10−18 s) time resolution having wide ranging physical, chemical, material science and biological applications. The quintessential and one of the most fundamental processes in this domain is the generation of phase locked XUV attosecond pulses. The theoretical approach to understand the process incorporates a fully quantum or semi classical or relativistic description of coherent charge dynamics in intense ultrashort electromagnetic fields driving a quantum system (an atom, a molecule, solid band gap materials or surface plasmas). Modelling of such physical and dynamical systems in science and also in many other branches often leads to equations represented in terms of complex multi-dimensional integrals. These integrals can often be solved using the stationary phase approximation, which leads to a series of equations identifying the points in the multi-dimensional space, having most significant contributions in their evaluation. These points are usually indicated as saddle points. The description of the dynamics of quantum mechanical or relativistic systems that results from such an approach enables near to classical physics intuitive perceptions of the processes under investigation. Thus, the saddle point methods are very powerful and valuable general theoretical tools to obtain asymptotic expressions of such solutions and help also to gain physical insights on the underlying phenomena. Such techniques developed in the past have been adapted to study the emission of as pulses by different physical systems and have been widely employed in calculating and estimating the response of matter to intense electromagnetic pulses on ultrafast time scales. Here we provide an extensive disposition of the saddle point approaches unifying their ubiquitous applications within the domain of attoscience valid for simple atomic to more complex condensed matter systems undergoing ultrafast dynamics and present current trends and advancements in the field. In this review we would delineate the methodology, present a synthesis of seminal works and describe the state of the art applications. Finally we also address ultrashort time dynamics of novel materials that have gained much attention recently, namely lower dimensional material systems and micro-plasma systems.
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| 9. |
- Neoričić, Lana, et al.
(författare)
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4D spatio-temporal electric field characterization of ultrashort light pulses undergoing filamentation
- 2022
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Ingår i: Optics Express. - 1094-4087. ; 30:15, s. 27938-27950
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Tidskriftsartikel (refereegranskat)abstract
- We present an experimental method capable of capturing the complete spatiotemporal dynamics of filamenting ultrashort laser pulses. By employing spatially resolved Fourier transform spectrometry in combination with the capability to terminate the filament at any length, we can follow the nonlinear dynamics in four dimensions, i.e. the transverse domain, time and filament length. Our method thus not only enables the full characterization of the filamentation process throughout its evolution, but also allows to identify and select laser pulses with desired parameters.
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| 10. |
- Neoricic, Lana
(författare)
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Generation and metrology of ultrashort pulses and their application in attosecond science
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with the dynamical processes in atoms and small molecules initiated by the absorption of ultrashort, coherent light pulses. The studied phenomena takeplace on the femtosecond (1 fs = 10−15 s) and attosecond (1 as = 10−18 s) timescales and critically depend on the properties of the light fields that drive them. Wework with infrared (IR) femtosecond laser pulses, which we manipulate through nonlinear interactions with matter to either study these interactions themselves or applythem to investigate other light-induced processes.One part of this thesis focuses on the generation and characterisation of IR pulses spectrally broadened through the Kerr effect. We use a technique called dispersion scanto temporally compress and at the same time measure pulses broadened in gas-filled hollow-core fibres. We propose multiple improvements to this well-established characterisation technique. Further, we investigate femtosecond filamentation in gases, a process with highly complex dynamics involving several non-linear processes including the Kerr effect and ionisation. We develop a method that allows us to measure the electric field of a laser pulse undergoing filamentation in three dimensions, whilealso scanning along the filament length. Our technique provides access to pulses with desirable characteristics that may be generated at a point inside the filament, simultaneously enabling their measurement and extraction for applications. In addition, this technique opens up the possibility to explore intricate filament dynamics.In the other part of this work, we up-convert the IR laser pulses into trains of extreme ultraviolet (XUV) attosecond pulses through a non-linear process called high-orderharmonic generation. We combine the IR and XUV pulses to study the photoionisation dynamics in different species using a method known as RABBIT (Reconstructionof Attosecond Beating By Interference of Two-photon transitions). In this technique, a target gas is ionised by the XUV field, creating an electron wave-paket (EWP) in thecontinuum, while a weak IR pulse probes the system. The EWP scatters off the ionic potential, acquiring an additional phase as it propagates. Recording the photoelectronspectrum as a function of the IR-XUV time delay allows us to infer time-resolved information about the ionic potential. We apply this method to investigate the dynamicsof different ionisation processes in noble gases (He, Ar, and Xe) and the N2 molecule. The high spectral resolution of our electron spectrometer allows us to disentanglethe contributions from different ionisation channels. In addition, we perform angle-resolved measurements, investigating the coherent superposition of final stateswith different angular momenta.
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