| 1. |
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| 2. |
- Alkhazov, GD, et al.
(author)
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SPES4-pi: installation for exclusive study of nuclear reactions
- 2005
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In: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 551:2-3, s. 290-311
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Journal article (peer-reviewed)abstract
- The paper describes the spectrometric system "SPES4-pi" used at the National Laboratory Saturne (CE Saclay, France) for the exclusive study of the baryon resonance excitation in inelastic alpha and d scattering on the proton, as well as coherent pion production in charge exchange reactions. The system consists of the magnetic spectrometer SPES4 and two wide-aperture position-sensitive detector arrays, equipped with wire chambers and scintillator hodoscopes, installed around a large-gap C-shape dipole magnet.
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| 3. |
- Antoine, P, et al.
(author)
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Generation of attosecond pulses in macroscopic media
- 1997
-
In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 56:6, s. 4960-4969
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Journal article (peer-reviewed)abstract
- We describe theoretically the generation of ultrashort (subfemtosecond) pulses using high-order harmonics of a laser pulse with a time-dependent degree of ellipticity. The single-atom response is calculated by using a low-frequency strong-field approximation. Propagation effects are taken into account using a method going beyond the slowly varying envelope approximation. Propagation modifies significantly the results obtained in the single-atom response and, in certain conditions, makes the generation of one attosecond pulse possible. We discuss prospects for the observation of these ultrashort pulses. [S1050-2947(97)09411-0].
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| 4. |
- L'Huillier, Anne, et al.
(author)
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High-order Harmonics - A Coherent Source In the Xuv Range
- 1995
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In: Journal of Nonlinear Optical Physics & Materials. - 0218-1991. ; 4:3, s. 647-665
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Journal article (peer-reviewed)abstract
- We review the main results concerning high-order generation processes from the point of view of a potential user of this new source of XUV radiation. The perspectives for optimizing the source, both in efficiency and in spectral range, its characteristics and in particular, its coherence properties, are discussed. Finally, we describe two experiments, which demonstrate the usefulness of the harmonics as a short-pulse, coherent source in the XUV domain.
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| 5. |
- Bellini, M, et al.
(author)
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Temporal coherence of ultrashort high-order harmonic pulses
- 1998
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In: Physical Review Letters. - 1079-7114. ; 81:2, s. 297-300
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Journal article (peer-reviewed)abstract
- We have studied the temporal coherence of high-order harmonics (up to the 15th order) produced by focusing 100 fs laser pulses into an argon gas jet. We measure the visibility of the interference fringes, produced when two spatially separated harmonic sources interfere in the far field, as a function of the time delay between the two sources. In general, we find long coherence times, comparable to the expected pulse durations of the harmonics. For some of the harmonics, the interference pattern exhibits two regions, with significantly different coherence times. These results are interpreted in terms of different electronic trajectories contributing to harmonic generation. [S0031-9007(98)05569-7].
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| 6. |
- Bengtsson, S., et al.
(author)
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Space–time control of free induction decay in the extreme ultraviolet
- 2017
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In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 11:4, s. 252-258
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Journal article (peer-reviewed)abstract
- Ultrafast extreme-ultraviolet (XUV) and X-ray sources are revolutionizing our ability to follow femtosecond processes with ångström-scale resolution. The next frontier is to simultaneously control the direction, duration and timing of such radiation. Here, we demonstrate a fully functional opto-optical modulator for XUV light, similar to modulators available at infrared (IR) and visible wavelengths. It works by using an IR pulse to control the spatial and spectral phase of the free induction decay that results from using attosecond pulses to excite a gas. The modulator allows us to send the XUV light in a direction of our choosing at a time of our choosing. The inherent synchronization of the XUV emission to the control pulse will allow laser-pump/X-ray probe experiments with sub-femtosecond time resolution.
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| 7. |
- Gademann, G., et al.
(author)
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Attosecond control of electron-ion recollision in high harmonic generation
- 2011
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In: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 13
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Journal article (peer-reviewed)abstract
- We show that high harmonic generation driven by an intense near-infrared (IR) laser can be temporally controlled when an attosecond pulse train (APT) is used to ionize the generation medium, thereby replacing tunnel ionization as the first step in the well-known three-step model. New harmonics are formed when the ionization occurs at a well-defined time within the optical cycle of the IR field. The use of APT-created electron wave packets affords new avenues for the study and application of harmonic generation. In the present experiment, this makes it possible to study harmonic generation at IR intensities where tunnel ionization does not give a measurable signal.
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| 8. |
- Mansten, Erik, et al.
(author)
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Spectral signature of short attosecond pulse trains.
- 2009
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In: Physical Review Letters. - 1079-7114. ; 102:8
-
Journal article (peer-reviewed)abstract
- We report experimental measurements of high-order harmonic spectra generated in Ar using a carrier-envelope-offset (CEO) stabilized 12 fs, 800 nm laser field and a fraction (less than 10%) of its second harmonic. Additional spectral peaks are observed between the harmonic peaks, which are due to interferences between multiple pulses in the train. The position of these peaks varies with the CEO and their number is directly related to the number of pulses in the train. An analytical model, as well as numerical simulations, support our interpretation.
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| 9. |
- Olofsson, A., et al.
(author)
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Opto-optical modulator (OOM) for extreme ultraviolet pulses
- 2020. - 7
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In: Attosecond Physics. - : IOP Publishing. - 1742-6588. ; 1412
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Conference paper (peer-reviewed)abstract
- There is a profound, almost symbiotic relation between electrons and photons. When light interacts with matter the electrons in the material will start to move and oscillate. When a charged particle, such as an electron, oscillates it will act as a dipole and emit light. We utilize this symbiotic relation and extend the control of light to the extreme ultraviolet (XUV) region using the newly developed XUV opto-optical modulator.
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| 10. |
- Ramstein, B, et al.
(author)
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H-2(He-3, t)2p reaction at 2 GeV
- 2003
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In: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 16:4, s. 583-597
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Journal article (peer-reviewed)abstract
- The exclusive H-2 (He-3, t)2p reaction has been studied at 2 GeV for energy transfers up to 500 MeV and triton angles up to 3.4degrees. The protons were measured in the large acceptance magnetic detector DIOGENE, in coincidence with the forward tritons detected in a dedicated magnetic arm. The energy transfer spectra extend well above the pion threshold. However, in the region of Delta excitation, the yield is less than 10% of the inclusive H-2(He-3, t) cross-section, which indicates the small contribution of the DeltaN --> NN process. The angular distributions of the two protons in their center of mass have been analysed as a function of energy transfer and triton angle and a Legendre polynomial decomposition has been achieved. These data have been compared to a model based on a coupled-channel approach for describing the NN and NDelta systems.
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| 11. |
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| 12. |
- Simpson, E. R., et al.
(author)
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Probing Stark-induced nonlinear phase variation with opto-optical modulation
- 2019
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In: Physical Review A. - 2469-9926. ; 100:2
-
Journal article (peer-reviewed)abstract
- We extend the recently developed technique of opto-optical modulation (OOM) to probe state-resolved ac-Stark-induced phase variations of a coherently excited ensemble of helium atoms. In a joint experimental and theoretical study, we find that the spatial redirection of the resonant emission from the OOM process is different for the low-lying 1s2p state as compared with the higher-lying Rydberg states, and that this redirection can be controlled through the spatial characteristics of the infrared (IR) probe beam. In particular, we observe that the intensity dependence of the IR-induced Stark phase on the 1s2p emission is nonlinear, and that the phase accumulation changes sign for moderate intensities. Our results suggest that OOM, combined with precise experimental shaping of the probe beam, could allow future measurements of Stark-induced phase shifts of excited states.
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| 13. |
- Zerne, R, et al.
(author)
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Phase-locked high-order harmonic sources
- 1997
-
In: Physical Review Letters. - 1079-7114. ; 79:6, s. 1006-1009
-
Journal article (peer-reviewed)abstract
- We demonstrate that two harmonic sources generated independently in a xenon gas jet using the same picosecond Nd:YAG laser are locked in phase. The experiment is performed by separating a laser beam into two parallel beams focused at different locations under the nozzle of a gas jet, and therefore producing two independent sources of harmonic radiation, and studying the pattern obtained in the far field when the radiations from these sources interfere. A high and robust fringe visibility is obtained.
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| 14. |
- Johnsson, Per, et al.
(author)
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Attosecond electron wave packet dynamics in strong laser fields
- 2005
-
In: Physical Review Letters. - 1079-7114. ; 95:1, s. 1-013001
-
Journal article (peer-reviewed)abstract
- We use a train of sub-200 attosecond extreme ultraviolet (XUV) pulses with energies just above the ionization threshold in argon to create a train of temporally localized electron wave packets. We study the energy transfer from a strong infrared (IR) laser field to the ionized electrons as a function of the delay between the XUV and IR fields. When the wave packets are born at the zero crossings of the IR field, a significant amount of energy (similar to 20 eV) is transferred from the field to the electrons. This results in dramatically enhanced above-threshold ionization in conditions where the IR field alone does not induce any significant ionization. Because both the energy and duration of the wave packets can be varied independently of the IR laser, they are valuable tools for studying and controlling strong-field processes.
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| 15. |
- Lopez, Rodrigo, et al.
(author)
-
Amplitude and phase control of attosecond light pulses
- 2005
-
In: Physical Review Letters. - 1079-7114. ; 94:3
-
Journal article (peer-reviewed)abstract
- We report the generation, compression, and delivery on target of ultrashort extreme-ultraviolet light pulses using external amplitude and phase control. Broadband harmonic radiation is first generated by focusing an infrared laser with a carefully chosen intensity into a gas cell containing argon atoms. The emitted light then goes through a hard aperture and a thin aluminum filter that selects a 30-eV bandwidth around a 30-eV photon energy and synchronizes all of the components, thereby enabling the formation of a train of almost Fourier-transform-limited single-cycle 170 attosecond pulses. Our experiment demonstrates a practical method for synthesizing and controlling attosecond waveforms.
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| 16. |
- Mauritsson, Johan, et al.
(author)
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Attosecond pulse trains generated using two color laser fields
- 2006
-
In: Physical Review Letters. - 1079-7114. ; 97:1
-
Journal article (peer-reviewed)abstract
- We investigate the spectral and temporal structure of high harmonic emission from argon exposed to an infrared laser field and its second harmonic. For a wide range of generating conditions, trains of attosecond pulses with only one pulse per infrared cycle are generated. The synchronization necessary for producing such trains ensures that they have a stable pulse-to-pulse carrier envelope phase, unlike trains generated from one color fields, which have two pulses per cycle and a pi phase shift between consecutive pulses. Our experiment extends the generation of phase stabilized few cycle pulses to the extreme ultraviolet regime.
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| 17. |
- Neoričić, Lana, et al.
(author)
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4D spatio-temporal electric field characterization of ultrashort light pulses undergoing filamentation
- 2022
-
In: Optics Express. - 1094-4087. ; 30:15, s. 27938-27950
-
Journal article (peer-reviewed)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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| 18. |
- Roos, L, et al.
(author)
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Controlling phase matching of high-order harmonic generation by manipulating the fundamental field
- 1999
-
In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 60:6, s. 5010-5018
-
Journal article (peer-reviewed)abstract
- We study experimentally how to control and improve phase matching of high-order harmonic generation. We use a birefringent lens and a birefringent compensator to obtain a fundamental laser pulse (150 fs, 800 nm, similar to 4 mJ) With two foci Separated by 6.2 mm along the propagation axis and with a controllable phase delay between the polarizations along the optic axes of the birefringent optical components. This enables us to enhance the high-order harmonic conversion efficiency for the high-order harmonics in neon to 3 x 10(-8), a factor of 4 higher compared to a single-focus setup in similar conditions. The enhancement is achieved by improving the phase matching and at the same time maintaining a high intensity in a large generating volume. [S1050-2947(99)04512-6].
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| 19. |
- Roos, L, et al.
(author)
-
Tailoring harmonic radiation to different applications using a genetic algorithm
- 2001
-
In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 34:24, s. 5041-5054
-
Journal article (peer-reviewed)abstract
- We use a genetic algorithm to theoretically optimize several properties of extreme ultraviolet (XUV) radiation, generated as high-order harmonics in xenon and argon. We maximize the harmonic pulse energy, minimize the pulse duration or optimize the temporal coherence by varying at the same time two or three parameters that are easily accessible in experiments, related to the characteristics of the laser beam and the nonlinear medium. For the 15th and 29th harmonies in argon, we find up to 10(9) photons per pulse, and pulse durations as short as 6 fs generated by a 50 fs laser pulse. We can also tailor the phase matching conditions to spectrally select the transform-limited part of the harmonic radiation. This allows us to identify conditions when the time structure of the XUV radiation presents a train of attosecond pulses. We find that the optimum conditions for the different properties are in general not the same. They depend in particular on whether the harmonic belongs to the plateau or the cutoff region of the harmonic spectrum. This reflects the unavoidable interplay between the microscopic intensity-dependent harmonic phase and the macroscopic phase matching conditions imposed by a nonlinear medium interacting with an intense, focused laser beam.
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| 20. |
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