| 1. |
- Bergues, B., et al.
(författare)
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Nonlinear interaction of 100-eV attosecond XUV-pulses with core electrons in Xenon
- 2018
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Ingår i: Optics InfoBase Conference Papers. - : Optica Publishing Group. - 9781557528209
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Konferensbidrag (refereegranskat)abstract
- We demonstrate multiphoton ionization of inner-shell electrons in Xenon with 100-eV attosecond pulses. This was achieved with a novel XUV source based on high-harmonic generation in the gas phase driven with multi-TW few-cycle laser pulses.
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| 2. |
- Bergues, B., et al.
(författare)
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Tabletop nonlinear optics in the 100-eV spectral region
- 2018
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Ingår i: Optica. - : Optical Society of America. - 2334-2536. ; 5:3, s. 237-242
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Tidskriftsartikel (refereegranskat)abstract
- Nonlinear light-matter interactions in the extreme ultraviolet (XUV) are a prerequisite to perform XUV-pump/XUV-probe spectroscopy of core electrons. Such interactions are now routinely investigated at free-electron laser (FEL) facilities. Yet, electron dynamics are often too fast to be captured with the femtosecond resolution of state-of-the-art FELs. Attosecond pulses from laser-driven XUV-sources offer the necessary temporal resolution. However, intense attosecond pulses supporting nonlinear processes have only been available for photon energy below 50 eV, precluding XUV-pump/XUV-probe investigation of typical inner-shell processes. Here, we surpass this limitation by demonstrating two-photon absorption from inner electronic shells of xenon at photon energies around 93 eV and 115 eV. This advance opens the door for attosecond real-time observation of nonlinear electron dynamics deep inside atoms.
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| 3. |
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| 4. |
- de Andres Gonzalez, Aitor, et al.
(författare)
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Simple measurement technique for spatio-temporal couplings in few-cycle pulses
- 2022
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Ingår i: The International Conference on Ultrafast Phenomena (UP) 2022. - : Optica Publishing Group (formerly OSA). - 9781557528209
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We report on the detection of spatio-temporal couplings in a 700-1000 nm NOPA using an optimized characterization method. The technique is performed during normal focus observation and requires little additional hardware.
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| 5. |
- de Andres Gonzalez, Aitor, et al.
(författare)
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Spatio-spectral couplings in optical parametric amplifiers
- 2023
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Ingår i: Optics Express. - : Optica Publishing Group. - 1094-4087. ; 31:8, s. 12036-12048
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Tidskriftsartikel (refereegranskat)abstract
- Optical parametric amplification (OPA) is a powerful tool for the generation of ultrashort light pulses. However, under certain circumstances, it develops spatio-spectral couplings, color dependent aberrations that degrade the pulse properties. In this work, we present a spatio-spectral coupling generated by a non-collimated pump beam and resulting in the change of direction of the amplified signal with respect to the input seed. We experimentally characterize the effect, introduce a theoretical model to explain it as well as reproduce it through numerical simulations. It affects high-gain non-collinear OPA configurations and becomes especially relevant in sequential optical parametric synthesizers. In collinear configuration, however, beyond the direction change, also angular and spatial chirp is produced. We obtain with a synthesizer about 40% decrease in peak intensity in the experiments and local elongation of the pulse duration by more than 25% within the spatial full width at half maximum at the focus. Finally, we present strategies to correct or mitigate the coupling and demonstrate them in two different systems. Our work is important for the development of OPA-based systems as well as few-cycle sequential synthesizers.
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| 6. |
- Major, B., et al.
(författare)
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Investigation of high harmonic generation using a high-power, 5-fs laser in a loose-focusing geometry
- 2017
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Ingår i: 2017 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC). - : IEEE. - 9781509067367
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Konferensbidrag (refereegranskat)abstract
- Summary form only given. Since its first observation almost three decades ago high-order harmonic generation (HHG) in gases became a reliable source of extreme ultraviolet (XUV) pulses, which gave the possibility to study electronic processes on their natural timescale [1, 2]. While the main building blocks of the experimental setups for gas HHG are the same in almost all cases, the focusing or medium geometry varies from realization to realization based on, for example, the available laser power [3, 4].In this work we study HHG in a loose focusing geometry by focusing a ~50-mm diameter (FWHM) beam with a mirror of 16-m focal length (f-number ~320). The main subject of this analysis is to compare low pressure - long interaction length (few millibars and tens of centimeters) with high pressure - short medium (hundreds of millibars and a few millimeters) scenarios and understand the underlying reasons for the observed XUV radiation parameters. The experiments are carried out with on target 35 mJ, sub-5 fs, 740 nm central wavelength pulses provided by an optical parametric synthesizer [5], producing high-energy pulses at the 100 eV spectral region [6]. The theoretical analysis is performed by simulation code based on a three-dimensional nonadiabatic model [7,8]. The good agreement between the experimental and simulation data (see Fig. 1) allows us to use the theoretical findings to gain better insight on the exact phase-matching processes providing the observed features. This detailed description is used to draw general conclusions of the high-harmonic generation process.
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| 7. |
- Muschet, Alexander A., 1990-, et al.
(författare)
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An easy technique for focus characterization and optimization of XUV and soft X-ray pulses
- 2022
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Ingår i: Applied Sciences. - : MDPI. - 2076-3417. ; 12:11
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Tidskriftsartikel (refereegranskat)abstract
- For many applications of extreme ultraviolet (XUV) and X-ray pulses, a small focus size is crucial to reach the required intensity or spatial resolution. In this article, we present a simple way to characterize an XUV focus with a resolution of 1.85 µm. Furthermore, this technique was applied for the measurement and optimization of the focus of an ellipsoidal mirror for photon energies ranging from 18 to 150 eV generated by high-order harmonics. We envisage a broad range of applications of this approach with sub-micrometer resolution from high-harmonic sources via synchrotrons to free-electron lasers.
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| 8. |
- Muschet, Alexander A., 1990-, et al.
(författare)
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Utilizing the temporal superresolution approach in an optical parametric synthesizer to generate multi-TW sub-4-fs light pulses
- 2022
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Ingår i: Optics Express. - : The Optical Society. - 1094-4087. ; 30:3, s. 4374-4380
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Tidskriftsartikel (refereegranskat)abstract
- The Fourier-transform limit achieved by a linear spectral phase is the typical optimum by the generation of ultrashort light pulses. It provides the highest possible intensity, however, not the shortest full width at half maximum of the pulse duration, which is relevant for many experiments. The approach for achieving shorter pulses than the original Fourier limit is termed temporal superresolution. We demonstrate this approach by shaping the spectral phase of light from an optical parametric chirped pulse amplifier and generate sub-Fourier limited pulses. We also realize it in a simpler way by controlling only the amplitude of the spectrum, producing a shorter Fourier-limited duration. Furthermore, we apply this technique to an optical parametric synthesizer and generate multi-TW sub-4-fs light pulses. This light source is a promising tool for generating intense and isolated attosecond light and electron pulses.
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| 9. |
- Smijesh, N., et al.
(författare)
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Contrast improvement of sub-4 fs laser pulses using nonlinear elliptical polarization rotation
- 2019
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Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 44:16, s. 4028-4031
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Tidskriftsartikel (refereegranskat)abstract
- Temporal-intensity contrast is crucial in intense laser-matter interaction to circumvent the undesirable expansion of steep high-density plasma prior to the interaction with the main pulse. Nonlinear elliptical polarization rotation in an argon filled hollow-core fiber is used here for cleaning pedestals/satellite pulses of a chirped-pulse-amplifier based Ti: Sapphire laser. This source provides similar to 35 mu J energy and sub-4-fs duration, and the process has >50% internal efficiency, more than the most commonly used pulse cleaning methods. Further, the contrast is improved by 3 orders of magnitude when measured after amplifying the pulses to 16 TW using non-collinear optical parametric chirped pulse amplification with a prospect to even further enhancement.
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