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C. Altucci,
S. Amoruso,
R. Bruzzese, M. Nisoli,
I. Procino,
G. Sansone,
V. Tosa,
R. Velotta,
C. Vozzi,
J. Xia,
X. Wang
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C. Altucci,
S. Amoruso,
R. Bruzzese, M. Nisoli,
I. Procino,
G. Sansone,
V. Tosa,
R. Velotta,
C. Vozzi,
J. Xia,
X. Wang
[show abstract]
[hide abstract]
ABSTRACT: The compression of laser pulses at 527 nm, 250 fs long, down to 30 fs is reported. The laser pulses, originated from a frequency-doubled,
mode-locked Nd:glass laser, were compressed by a 0.7-m-long, 150-μ m-bore-diameter argon-filled hollow fiber and a pair of
SF10 prisms with a final energy of 160 μJ. These are the shortest, high energy pulses ever produced by direct pulse compression
at the central wavelength of 527 nm. The spectral broadening of the pulses propagating inside the hollow fiber was experimentally
examined for various filling-gas pressures and input pulse energies. The physical limitations of the hollow-fiber pulse compression
technique applied in the visible range are also studied. An application to laser ablation of Ni target is performed. Metal
nanoparticles are obtained both with the 250-fs and with the 30-fs pulse.
The European Physical Journal Special Topics 04/2012; 175(1):11-14. · 1.56 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We analyze the emission of coherent XUV radiation in gaseous targets by high-order harmonics of tunable infrared (1.4–1.6
μm) laser pulses generated by a parametric source. As noticeable application, we show that a continuous spectrum spanning
the 40–200 eV region can be efficiently generated by mixing the infrared pulses with visible pulses at 800 nm. These results
open new perspectives for the extension of attosecond physics towards the soft-X region and for the investigation of atoms
and molecules on a broader range of photon energies with respect to the state of the art.
Laser Physics 04/2012; 20(5):1019-1027. · 3.61 Impact Factor
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A. Gazibegović-Busuladžić,
E. Hasović,
M. Busuladžić,
D. B. Milošević,
F. Kelkensberg,
W. K. Siu,
M. J. J. Vrakking,
F. Lépine,
G. Sansone, M. Nisoli,
I. Znakovskaya,
M. F. Kling
[show abstract]
[hide abstract]
ABSTRACT: Above-threshold ionization of diatomic molecules by infrared carrier-envelope phase (CEP) stable few-cycle laser pulses is analyzed both experimentally and theoretically. The theoretical approach is based on the recently developed molecular improved strong-field approximation (ISFA), generalized to few-cycle pulses. Instead of using the first Born approximation, the rescattering matrix element in the ISFA is now calculated exactly. This modification leads to the appearance of characteristic minima in the differential cross section as a function of the scattering angle. Experimental angle-resolved photoelectron spectra of N2 and O2 molecules are obtained using the velocity map imaging technique. A relatively good agreement of experimental and simulated angle-resolved spectra, CEP-dependent asymmetry maps, and extracted electron-molecular ion elastic scattering differential cross sections is obtained.
Phys. Rev. A. 10/2011; 84(4).
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N D Ouart,
A S Safronova,
A Ya Faenov,
T A Pikuz,
S V Gasilov,
S Stagira,
F Calegari, M Nisoli,
S De Silvestri,
L Poletto,
P Villoresi
[show abstract]
[hide abstract]
ABSTRACT: High resolution X-ray spectra of plasmas produced by the interaction of Ti:Sa laser pulses (duration from 60 fs to 1 ps, and energy from 15 mJ to 128 mJ) with a solid Fe target are investigated experimentally and theoretically. Interestingly, both L-shell and K-shell Fe spectra were simultaneously measured while changing the time-duration of the laser experiments. In particular, the L-shell Fe radiation from F-, Ne-, and Na-like ions between ~14–16.3 Å were observed from the first order reflection with a mica crystal. Simultaneously measured alongside the L-shell radiation was the Fe cold Kα lines (~1.94 Å), from 8th order reflection. Two non-LTE Fe kinetic models have been developed to account for the L-shell radiation from the Fe ions and for the K-shell radiation from the low ionization stages emitting the Fe cold Kα lines. Preliminary analysis of the simultaneously measured Fe L- and K-shell radiations from changing the time-duration of the experiments shows varying relative line intensities from different ionization stages. Resulting plasma parameters as well as the opacity of the strongest resonance line, 3C, and their dependence on changing the time-duration will be discussed.
Journal of Physics Conference Series 09/2010; 244(4):042004.
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J Mauritsson,
T Remetter,
M Swoboda,
K Klünder,
A L'Huillier,
K J Schafer,
O Ghafur,
F Kelkensberg,
W Siu,
P Johnsson,
M J J Vrakking,
I Znakovskaya,
T Uphues,
S Zherebtsov,
M F Kling,
F Lépine,
E Benedetti,
F Ferrari,
G Sansone, M Nisoli
[show abstract]
[hide abstract]
ABSTRACT: We present an interferometric pump-probe technique for the characterization of attosecond electron wave packets (WPs) that uses a free WP as a reference to measure a bound WP. We demonstrate our method by exciting helium atoms using an attosecond pulse (AP) with a bandwidth centered near the ionization threshold, thus creating both a bound and a free WP simultaneously. After a variable delay, the bound WP is ionized by a few-cycle infrared laser precisely synchronized to the original AP. By measuring the delay-dependent photoelectron spectrum we obtain an interferogram that contains both quantum beats as well as multipath interference. Analysis of the interferogram allows us to determine the bound WP components with a spectral resolution much better than the inverse of the AP duration.
Physical Review Letters 07/2010; 105(5):053001. · 7.37 Impact Factor
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G Sansone,
F Kelkensberg,
J F Pérez-Torres,
F Morales,
M F Kling,
W Siu,
O Ghafur,
P Johnsson,
M Swoboda,
E Benedetti,
F Ferrari,
F Lépine,
J L Sanz-Vicario,
S Zherebtsov,
I Znakovskaya,
A L'huillier,
M Yu Ivanov, M Nisoli,
F Martín,
M J J Vrakking
[show abstract]
[hide abstract]
ABSTRACT: For the past several decades, we have been able to directly probe the motion of atoms that is associated with chemical transformations and which occurs on the femtosecond (10(-15)-s) timescale. However, studying the inner workings of atoms and molecules on the electronic timescale has become possible only with the recent development of isolated attosecond (10(-18)-s) laser pulses. Such pulses have been used to investigate atomic photoexcitation and photoionization and electron dynamics in solids, and in molecules could help explore the prompt charge redistribution and localization that accompany photoexcitation processes. In recent work, the dissociative ionization of H(2) and D(2) was monitored on femtosecond timescales and controlled using few-cycle near-infrared laser pulses. Here we report a molecular attosecond pump-probe experiment based on that work: H(2) and D(2) are dissociatively ionized by a sequence comprising an isolated attosecond ultraviolet pulse and an intense few-cycle infrared pulse, and a localization of the electronic charge distribution within the molecule is measured that depends-with attosecond time resolution-on the delay between the pump and probe pulses. The localization occurs by means of two mechanisms, where the infrared laser influences the photoionization or the dissociation of the molecular ion. In the first case, charge localization arises from quantum mechanical interference involving autoionizing states and the laser-altered wavefunction of the departing electron. In the second case, charge localization arises owing to laser-driven population transfer between different electronic states of the molecular ion. These results establish attosecond pump-probe strategies as a powerful tool for investigating the complex molecular dynamics that result from the coupling between electronic and nuclear motions beyond the usual Born-Oppenheimer approximation.
Nature 06/2010; 465(7299):763-6. · 36.28 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: In this work we discuss our recent advances in attosecond technology. Isolated attosecond pulses with pulse duration down to 130 as are now routinely generated by using the polarization gating technique, in combination with few‐optical‐cycle driving pulses with controlled electric field, generated by the hollow‐fiber compression method. By using a high‐energy infrared parametric source with self‐stabilization of the carrier‐envelope phase, in combination with a two‐color excitation scheme, continuous XUV spectra were generated, showing a spectral extension beyond 200 eV. These results represent a step forward in the extension of attosecond science towards the soft‐X rays region.
AIP Conference Proceedings. 04/2010; 1228(1):400-407.
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[show abstract]
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ABSTRACT: A temporal gating on the high-order harmonic emission process is achieved using an intense 20 fs, 1.45 microm pulse (IR) in combination with an intense 13 fs, 800 nm pulse [visible (VIS)]. Exploiting this two-color gating scheme, a coherent continuous emission extending up to 160 eV using Ar gas and 200 eV using Ne gas is efficiently generated. The IR pulse contributes to significantly extending the harmonic emission to higher photon energies, whereas the VIS pulse improves the conversion efficiency of the process. These results indicate the possibility to produce bright attosecond pulses approaching the soft X spectral region.
Optics Letters 10/2009; 34(20):3125-7. · 3.40 Impact Factor
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F Kelkensberg,
C Lefebvre,
W Siu,
O Ghafur,
T T Nguyen-Dang,
O Atabek,
A Keller,
V Serov,
P Johnsson,
M Swoboda,
T Remetter,
A L'Huillier,
S Zherebtsov,
G Sansone,
E Benedetti,
F Ferrari, M Nisoli,
F Lépine,
M F Kling,
M J J Vrakking
[show abstract]
[hide abstract]
ABSTRACT: We present a combined theoretical and experimental study of ultrafast wave-packet dynamics in the dissociative ionization of H_{2} molecules as a result of irradiation with an extreme-ultraviolet (XUV) pulse followed by an infrared (IR) pulse. In experiments where the duration of both the XUV and IR pulses are shorter than the vibrational period of H_{2};{+}, dephasing and rephasing of the vibrational wave packet that is formed in H_{2};{+} upon ionization of the neutral molecule by the XUV pulse is observed. In experiments where the duration of the IR pulse exceeds the vibrational period of H_{2};{+} (15 fs), a pronounced dependence of the H;{+} kinetic energy distribution on XUV-IR delay is observed that can be explained in terms of the adiabatic propagation of the H_{2};{+} wave packet on field-dressed potential energy curves.
Physical Review Letters 09/2009; 103(12):123005. · 7.37 Impact Factor
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C. Vozzi,
F. Calegari, M. Nisoli,
G. Sansone,
S. De Silvestri,
S. Stagira,
F. Frassetto,
L. Poletto,
P. Villoresi,
E. Balogh,
V. Tosa
[show abstract]
[hide abstract]
ABSTRACT: We investigated phase matching effects on high-order harmonics (HH) generated by a few-cycle parametric source in the near-IR. This source is characterized by 1.5 mum central wavelength, almost transform limited pulse duration of about 20 fs and pulse energy up to 1.2 mJ. The harmonic structure is resolved only on a portion of the spectrum, due to the finite instrumental resolution. We observed a significant dependence of the spectral features and cutoff extension on phase-matching condition in harmonics generated in argon. These features are well reproduced by HH calculation, taking into account macroscopic effects. For HH calculation we use the model which solves the propagation equation for the laser and for the harmonic fields making use of strong field approximation for the single dipole response. The spatial structure of the generated harmonic field, as well as their spectral/temporal characteristics were obtained and will be discussed in connection to the phase-matching generation conditions.
Lasers and Electro-Optics 2009 and the European Quantum Electronics Conference. CLEO Europe - EQEC 2009. European Conference on; 07/2009
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J. Mauritsson,
T. Remetter,
M. Swoboda,
K. Klunder,
A. L'Huillier,
K.J. Schafer,
O. Ghafur,
F. Kelkensberg,
W. Siu,
P. Johnsson,
M. Vrakking,
I. Znakovskaya,
T. Uphues,
S. Zherebtsov,
M.F. Kling,
F. Lepine,
E. Benedetti,
F. Ferrari,
G. Sansone, M. Nisoli
[show abstract]
[hide abstract]
ABSTRACT: A method to determine the dynamics of a bound wave packet excited by an attosecond pulse, while - for the first time - keeping track of its spectral content with high precision, is presented. The key idea is that coincident with the creation of the bound wave packet, a broad continuum wave packet is launched . This free wave packet serves as a reference when, after a variable delay, the bound wave packet is ionized by a 7 fs infrared laser pulse, locked in phase with the bound wave packet. The interference fringes observed in the photoelectron spectrum enable precise determination of the bound electron wave packet. As in Ramsey spectroscopy, the spectral precision is here set not by the bandwidth of the excitation pulse, but by the delay between the pump and probe pulses as well as the experimental energy resolution of the photoelectron spectrometer used.
Lasers and Electro-Optics 2009 and the European Quantum Electronics Conference. CLEO Europe - EQEC 2009. European Conference on; 07/2009
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[show abstract]
[hide abstract]
ABSTRACT: We demonstrate the generation of broadband extreme ultraviolet (XUV) continua by high order harmonic generation in neon using carrier-envelope phase (CEP) stabilized, few-cycle pulses with a time-dependent polarization. The XUV spectra can support isolated attosecond pulses with a duration of about 50 as, opening the possibility of achieving time resolution close to the atomic unit of time. A theoretical model that calculates the spectral and temporal characteristics of the XUV radiation emitted by a single atom is used to interpret the CEP dependence of the harmonic structures.
Journal of Physics B Atomic Molecular and Optical Physics 06/2009; 42(13):134005. · 1.88 Impact Factor
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[show abstract]
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ABSTRACT: In this review we report on recent advances in laser technology, which have contributed to the fast development of attosecond science. In particular we will concentrate on two experimental methods for the generation of high-peak-power, fewoptical-cycle laser pulses with controlled electric field, which are crucial for the generation of isolated attosecond pulses. The first method is the hollow-fiber compression technique, introduced in 1996 and now routinely used in several laboratories. So far, isolated attosecond pulses have been generated by using few-cycle pulses produced by such compression technique, in combination with active stabilization of the carrier-envelope phase. More recently, few-cycle pulses tunable in the infrared region have been generated by optical parametric amplification with passive stabilization of the carrier-envelope phase. Such parametric sources represent excellent drivers for the generation of harmonic radiation with an extended cutoff, and offer the possibility to extend attosecond science towards the soft-X rays region. Finally, we will briefly discuss the basic elements of attosecond metrology. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)
Laser Physics Letters 03/2009; 6(4):259 - 267. · 9.97 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: High-order harmonics were generated in a two-color scheme exploiting an infrared parametric source with self-stabilization of the carrier-envelope phase. A significant cutoff extension was observed with respect to single color, 800 nm driving pulses at comparable peak intensities. Exploiting the wavelength tuning of the parametric source in the 1.5–1.6 μm range, a continuous xuv spectrum extending from 36 to 70 eV was generated in krypton. A broader xuv continuum, extending beyond 100 eV, was observed in argon. These results represent a step forward in the extension of attosecond science toward the soft x-rays region and open new perspectives in the investigation of quantum effects in atoms and molecules.
Phys. Rev. A. 03/2009; 79(3).
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[show abstract]
[hide abstract]
ABSTRACT: Extreme-ultraviolet pulses, produced by high-order-harmonic generation, have been spectrally selected by a time-delay-compensated
monochromator. Temporal characterization has been obtained using cross-correlation method: pulses as short as 8 fs, with high
photon flux, have been measured.
12/2008: pages 881-883;
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[show abstract]
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ABSTRACT: We generated high-order harmonics with self-phase-stabilized near-IR pulses produced by a parametric source. We observed a
significant cutoff extension with respect to 800-nm driving pulses at comparable peak intensity
12/2008: pages 6-8;
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G. Sansone,
F. Kelkensberg,
M. F. Kling,
W. K. Siu,
O. Ghafur,
P. Johnsson,
S. Zherebtsov,
I. Znakovskaya,
T. Uphues,
E. Benedetti,
F. Ferrari,
F. Lépine,
M. Swoboda,
T. Remetter,
A. L’Huillier, M. Nisoli,
M. J. J. Vrakking
[show abstract]
[hide abstract]
ABSTRACT: We report experiments where an attosecond pulse launches a wavepacket on the dissociative state of D
2
+
, and a few-cycle IR pulse localizes the electron on one ionic fragment with attosecond sensitivity to the XUV-IR delay.
12/2008: pages 51-53;
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M.F. Kling,
S. Zherebtsov,
I. Znakovskaya,
T. Uphues,
G. Sansone,
E. Benedetti,
F. Ferrari, M. Nisoli,
F. Lepine,
M. Swoboda,
T. Remetter,
A. L'Huillier,
F. Kelkensberg,
W.K. Siu,
O. Ghafur,
P. Johnsson,
M.J.J. Vrakking
[show abstract]
[hide abstract]
ABSTRACT: We present one-color (IR) and two-color (single attosecond XUV pulse + IR) experiments where the sub-cycle evolution of the electric field of light is used to control the dissociative ionization of hydrogen and deuterium molecules.
Lasers and Electro-Optics, 2008 and 2008 Conference on Quantum Electronics and Laser Science. CLEO/QELS 2008. Conference on; 06/2008
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[show abstract]
[hide abstract]
ABSTRACT: We generated high-order harmonics with self-phase-stabilized near-IR pulses produced by a parametric source. We observed a significant cutoff extension whit respect to 800-nm driving pulses at comparable peak intensity. This result represents a step forward the generation of single attosecond pulses with photon energies exceeding 100 eV.
Lasers and Electro-Optics, 2008 and 2008 Conference on Quantum Electronics and Laser Science. CLEO/QELS 2008. Conference on; 06/2008
