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| 2. |
- L'Huillier, Anne, et al.
(författare)
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Applications of high-order harmonics
- 2003
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Ingår i: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 26:1, s. 91-98
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Tidskriftsartikel (refereegranskat)abstract
- We review applications of high-order harmonic generation in different fields of physics, from spectroscopic studies of atoms and molecules, to interferometry and plasma diagnostics and nonlinear optics.
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| 3. |
- Lopez, Rodrigo, et al.
(författare)
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Time-frequency characterization of high-order harmonic pulses
- 2003
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Ingår i: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 26:1, s. 105-109
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Tidskriftsartikel (refereegranskat)abstract
- We present energy-resolved cross-correlation measurements of extreme ultraviolet (XUV) pulses generated as high harmonics of femtosecond pulses from a 1 kHz titanium-sapphire laser. The harmonic pulses are probed by a fraction of the fundamental laser pulse at 800 nm, in a noncollinear geometry, allowing us to vary independently the parameters of the harmonic pump and near-infrared probe pulses. We measure the so-called "sidebands" in the photoelectron spectrum of argon corresponding to the absorption of a harmonic photon plus or minus one probe photon. Spectrally resolving the cross-correlation signal allows us to characterize the time-dependent frequency of the XUV pulse.
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| 4. |
- Norin, Johan, et al.
(författare)
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Time-frequency characterization of femtosecond extreme ultraviolet pulses.
- 2002
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Ingår i: Physical Review Letters. - 1079-7114. ; 88:19, s. 193901-193901
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Tidskriftsartikel (refereegranskat)abstract
- We present energy-resolved cross-correlation measurements of an extreme ultraviolet (XUV) pulse, generated as the fifth harmonic (15.5 eV) of an intense 80 fs laser pulse centered at 400 nm. Spectrally resolving the cross-correlation signal allows us to characterize the time-dependent frequency of the XUV pulse. We find that the fifth harmonic has a small negative chirp in excess of that predicted by perturbation theory. In addition, by manipulating the chirp of the driving laser we can induce and measure a positive or a negative chirp on the XUV pulse.
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| 5. |
- Zamith, S, et al.
(författare)
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The predissociation of highly excited states in acetylene by time-resolved photoelectron spectroscopy
- 2003
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 119:7, s. 3763-3773
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Tidskriftsartikel (refereegranskat)abstract
- We study the dynamics of highly excited states in acetylene initiated by an ultrashort vacuum ultraviolet laser pulse. Electronic states lying in the 4s-3d Rydberg region are excited with one femtosecond pulse, and the dynamic development of the states is monitored by a second short pulse which ionizes the system. We show that even for femtosecond pulses where the bandwidth of the exciting pulse covers several electronic states, it is possible to extract short decay lifetimes through time-resolved photoelectron spectroscopy by using a frequency-modulated (chirped) excitation pulse. We report decay lifetimes for the F 4(0)(2) and E 4-5(0)(2) states in acetylene, and for the E 4(0)(2) and E 5(0)(2) states in d-acetylene. The time evolution measured in the electron spectra is compared to decay spectra measured using ion yield and the differences in these results are discussed. (C) 2003 American Institute of Physics.
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| 6. |
- Hergott, JF, et al.
(författare)
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XUV interferometry using high-order harmonics: Application to plasma diagnostics
- 2001
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Ingår i: Laser and Particle Beams. - 0263-0346. ; 19:1, s. 35-40
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present and compare the two different XUV interferometric techniques using high-order harmonics that have been developed so far. The first scheme is based on the interference between two spatially separated phase-locked harmonic sources while the second uses two temporally separated harmonic sources. These techniques have been applied to plasma diagnostics in feasibility experiments where electron densities up to a few 1020 e[minus sign/cm3 have been measured with a temporal resolution of 200 fs. We present the main characteristics of each technique and discuss their respective potentials and limitations.
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| 7. |
- Norin, Johan
(författare)
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Characterisation and Applications of Ultrashort Extreme Ultraviolet Pulses
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- When a strong laser field interacts with free atoms, harmonics up to very high orders are created. This extreme ultraviolet (XUV) radiation has interesting properties, such as spatial and temporal coherence, short pulse duration and high brightness. This thesis concentrates on the temporal aspects of this radiation. A method to characterise the pulse duration and time-dependent frequency (chirp) of such harmonic pulses has been developed. To perform the characterisation, the energy and amplitude of a photoelectron peak, generated through ionization of a rare gas after absorption of one XUV and one infrared laser photon, is measured as a function of the delay between the two pulses. In addition, by manipulating the chirp of the driving laser, positive or negative chirp could be induced on the harmonic radiation. By creating two sources of mutually coherent harmonics and analysing the interference in the far field, the first-order autocorrelation function has been measured. By overlapping the two sources, a high order autocorrelation trace of the laser was recorded. An XUV monochromator capable of extracting single harmonic frequencies without stretching them in time has been designed. Experiments have been performed on a prototype working in the infrared wavelength region. High-order harmonics have been used to perform XUV interferometric measurements. The beams were divided in the infrared before the generation of harmonics. The thickness of aluminium filters and the electron density of a laser-produced plasma were determined. In another application, harmonics have been used to perform lifetime measurements of Rydberg states in acetylene.
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| 8. |
- Norin, Johan, et al.
(författare)
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Design of an extreme-ultraviolet monochromator free from temporal stretching
- 2004
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Ingår i: Applied Optics. - 2155-3165. ; 43:5, s. 1072-1081
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Tidskriftsartikel (refereegranskat)abstract
- High-order harmonic generation in gases by use of femtosecond lasers is a source of ultrashort pulses in the extreme-ultraviolet (XUV). For many applications it is necessary to select radiation of only one specific harmonic order without affecting the duration of the ultrashort pulse. A three-grating monochromator that meets this demand has been designed and modeled by ray tracing as well as by wave-optical simulations. The only remaining temporal stretching of an XUV pulse is due to distortion of the pulse front on the gratings and is predicted to be similar to1 fs. The design has been successfully tested in the near infrared. Finally, the monochromator is also capable of eliminating any existing linear chirp in the harmonic pulses, thus compressing them to shorter durations. (C) 2004 Optical Society of America.
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