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H Ruf,
C Handschin,
R Cireasa,
N Thiré,
A Ferré,
S Petit,
D Descamps, E Mével,
E Constant,
V Blanchet,
B Fabre,
Y Mairesse
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ABSTRACT: High order harmonic generation from clusters is a controversial topic: conflicting theories exist, with different explanations for similar experimental observations. From an experimental point of view, separating the contributions from monomers and clusters is challenging. By performing a spectrally and spatially resolved study in a controlled mixture of clusters and monomers, we are able to isolate a region of the spectrum where the emission purely originates from clusters. Surprisingly, the emission from clusters is depolarized, which is the signature of statistical inhomogeneous emission from a low-density source. The harmonic response to laser ellipticity shows that this generation is produced by a new recollisional mechanism, which opens the way to future theoretical studies.
Physical Review Letters 02/2013; 110(8):083902. · 7.37 Impact Factor
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Applied Physics B 01/2013; · 2.19 Impact Factor
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H Ruf,
C Handschin,
A Ferré,
N Thiré,
J B Bertrand,
L Bonnet,
R Cireasa,
E Constant,
P B Corkum,
D Descamps, [......],
P Larregaray, E Mével,
S Petit,
B Pons,
D Staedter,
H J Wörner,
D M Villeneuve,
Y Mairesse,
P Halvick,
V Blanchet
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ABSTRACT: We study theoretically and experimentally the electronic relaxation of NO(2) molecules excited by absorption of one ∼400 nm pump photon. Semiclassical simulations based on trajectory surface hopping calculations are performed. They predict fast oscillations of the electronic character around the intersection of the ground and first excited diabatic states. An experiment based on high-order harmonic transient grating spectroscopy reveals dynamics occurring on the same time scale. A systematic study of the detected transient is conducted to investigate the possible influence of the pump intensity, pump wavelength, and rotational temperature of the molecules. The quantitative agreement between measured and predicted dynamics shows that, in NO(2), high harmonic transient grating spectroscopy encodes vibrational dynamics underlying the electronic relaxation.
The Journal of chemical physics 12/2012; 137(22):224303. · 3.09 Impact Factor
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ABSTRACT: We study numerically the time-dependent HHG phase-matching in the laser beam having a flat-top radial intensity profile. A
flat-top profile is the key to produce similar ionization degree at the axis and at the periphery and thus to achieve simultaneous
phase-matched generation. Such a profile can be obtained experimentally by using two concentric phase plates that introduce
a specific phase shift between the central and the outer part of a focused Gaussian beam. We find realistic laser field parameters
and medium density that allow obtaining (after spectral filtering) single attosecond pulse using 10 fs driving laser pulse.
Our technique provides isolated attosecond pulse emission almost insensitive on the CEP of the laser pulse. Moreover, the
technique is effective both for the mid-plateau and the cut-off spectral range. In particular, the XUV from Ar target in the
cut-off spectral range (compatible with the Zr filter) provides isolated attosecond pulse with 185 as duration at a central
energy of 92 eV. Using achievable multi mJ 10 fs laser pulses this technique could provide attosecond pulses approaching the
μJ energy range.
The European Physical Journal Special Topics 05/2012; 175(1):15-20. · 1.56 Impact Factor
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W. Boutu,
T. Auguste,
O. Boyko,
I. Sola,
Ph. Balcou,
L. Binazon,
O. Gobert,
H. Merdji,
C. Valentin,
E. Constant, E. Mével,
B. Carré
[show abstract]
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ABSTRACT: We present experimental and numerical results on high-order-harmonic generation with a flat-top laser beam. We show that a simple binary tunable phase plate, made of two concentric glass plates, can produce a flat-top profile at the focus of a Gaussian infrared beam. Both experiments and numerical calculations show that there is a scaling law between the harmonic generation efficiency and the increase of the generation volume.
Phys. Rev. A. 12/2011; 84(6).
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H J Wörner,
J B Bertrand,
B Fabre,
J Higuet,
H Ruf,
A Dubrouil,
S Patchkovskii,
M Spanner,
Y Mairesse,
V Blanchet, E Mével,
E Constant,
P B Corkum,
D M Villeneuve
[show abstract]
[hide abstract]
ABSTRACT: Conical intersections play a crucial role in the chemistry of most polyatomic molecules, ranging from the simplest bimolecular reactions to the photostability of DNA. The real-time study of the associated electronic dynamics poses a major challenge to the latest techniques of ultrafast measurement. We show that high-harmonic spectroscopy reveals oscillations in the electronic character that occur in nitrogen dioxide when a photoexcited wave packet crosses a conical intersection. At longer delays, we observe the onset of statistical dissociation dynamics. The present results demonstrate that high-harmonic spectroscopy could become a powerful tool to highlight electronic dynamics occurring along nonadiabatic chemical reaction pathways.
Science 10/2011; 334(6053):208-12. · 31.20 Impact Factor
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R A Loch,
A Dubrouil,
R Sobierajski,
D Descamps,
B Fabre,
P Lidon,
R W E van de Kruijs,
F Boekhout,
E Gullikson,
J Gaudin,
E Louis,
F Bijkerk, E Mével,
S Petit,
E Constant,
Y Mairesse
[show abstract]
[hide abstract]
ABSTRACT: We characterize the phase shift induced by reflection on a multilayer mirror in the extreme UV range (80-93 eV) using two techniques: one based on high order harmonic generation and attosecond metrology (reconstruction of attosecond beating by interference of two-photon transitions), and a second based on synchrotron radiation and measurements of standing waves (total electron yield). We find an excellent agreement between the results from the two measurements and a flat group delay shift (±40 as) over the main reflectivity peak of the mirror.
Optics Letters 09/2011; 36(17):3386-8. · 3.40 Impact Factor
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[show abstract]
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ABSTRACT: We demonstrate controlled high-order harmonic generation in gas using high-energy femtosecond pulses (50 fs-50 mJ on target) by performing spatial shaping of the terrawatt fundamental laser beam. We have developed a two optical paths mirror that can withstand high power and shape the pump beam into a quasi-flat-top profile (super Gaussian) near focus. We observe clear signatures of the spatial shaping on the harmonic beam in terms of profile, divergence, level of signal, and spectrum. The harmonic generation in neon with a quasi-flat-top beam results in a broadband extreme UV beam with extremely low divergence (~340 μrad).
Optics Letters 07/2011; 36(13):2486-8. · 3.40 Impact Factor
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J Higuet,
H. Ruf,
N. ThirÉ,
R Cireasa,
E. Constant,
E Cormier,
D Descamps, E. Mével,
S Petit,
B. Pons,
Y. Mairesse,
B Fabre
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ABSTRACT: We study the Cooper minimum in high harmonic generation from argon atoms using long wavelength laser pulses. We find that the minimum in high harmonic spectra is systematically shifted with respect to total photoionization cross section measurements. We use a semi-classical theoretical approach based on Classical Trajectory Monte Carlo and Quantum Electron Scattering methods (CTMC-QUEST) to model the experiment. Our study reveals that the shift between photoionization and high harmonic emission is due to several effects: the directivity of the recombining electrons and emitted polarization, and the shape of the recolliding electron wavepacket. Comment: 13 pages
12/2010;
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Y Mairesse,
J Higuet,
N Dudovich,
D Shafir,
B Fabre, E Mével,
E Constant,
S Patchkovskii,
Z Walters,
M Yu Ivanov,
O Smirnova
[show abstract]
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ABSTRACT: We perform high harmonic generation spectroscopy of aligned nitrogen molecules to characterize the attosecond dynamics of multielectron rearrangement during strong-field ionization. We use the spectrum and ellipticity of the harmonic light to reconstruct the relative phase between different ionization continua participating in the ionization, and thus determine the shape and location of the hole left in the molecule by strong-field ionization. Our interferometric technique uses transitions between the ionic states, induced by the laser field on the subcycle time scale.
Physical Review Letters 05/2010; 104(21):213601. · 7.37 Impact Factor
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[show abstract]
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ABSTRACT: We present a new optical post-compression technique designed for high-energy ultrashort pulses. A large spectral broadening is achieved through rapid ionization of helium by an intense pulse (>10(15) W/cm(2)) propagating in a capillary filled with low-pressure helium. The blueshifted pulses are re-compressed with chirped mirrors and silica plates. From a terawatt Ti:sapphire laser chain providing pulses of 40 fs, 70 mJ, we demonstrate the compression of pulses down to 11.4 fs (FWHM) with a total output energy of 13.7 mJ.
Optics Letters 01/2010; 35(2):253-5. · 3.40 Impact Factor
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S. Haessler,
B. Fabre,
J. Higuet,
J. Caillat,
T. Ruchon,
P. Breger,
B. Carré,
E. Constant,
A. Maquet, E. Mével,
P. Salières,
R. Taïeb,
Y. Mairesse
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ABSTRACT: We photoionize nitrogen molecules with a train of extreme ultraviolet attosecond pulses together with a weak infrared field. We measure the phase of the two-color two-photon ionization transition (molecular phase) for different states of the ion. We observe a 0.9 shift for the electrons produced in the ionization channels leading to the X 2g+" align="middle"/>, v=1, and v=2 states. We relate this phase shift to the presence of a complex resonance in the continuum. By providing both a high spectral and temporal resolution, this general approach gives access to the evolution of extremely short-lived states, which is often not accessible otherwise.
Physical Review A (Atomic, Molecular, and Optical Physics). 01/2009; 80:011404--011404(R).
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E. Mével,
Y. Mairesse,
S. Haessler,
B. Fabre,
J. Higuet,
W. Boutu,
P. Breger,
E. Constant,
D. Descamps,
S. Petit,
D. Shafir,
H. Deleon,
N. Dudovich,
P. Salières
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ABSTRACT: High Harmonic generation can be used as a probe of the emitting medium with attosecond and Angström resolutions. We show that
polarization-resolved pump-probe spectroscopy with high harmonics improves the detection sensitivity of rotationally excited
molecules.
12/2008: pages 24-26;
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ABSTRACT: We present a new method for generating isolated attosecond pulses via high-order harmonic generation in gases. It relies on using collective effects to achieve transient phase-matching which provides both a high efficiency and a strong temporal confinement under specific conditions. By controlling the spatial shape of the fundamental beam and the geometry of the laser–gas interaction, this transient phase matching leads to the generation of isolated broadband attosecond pulses with long driving pulses (10–20 fs) even without controlling their carrier envelope phase. Such laser pulses are becoming available at high energy levels and our approach offers a route to increase the energy of isolated attosecond pulses by orders of magnitude as compared to existing sources.
New Journal of Physics 08/2008; 10(8):083040. · 4.18 Impact Factor
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Y. Mairesse,
S. Haessler,
B. Fabre,
J. Higuet,
W. Boutu,
P. Breger,
E. Constant,
D. Descamps, E. Mével,
S. Petit,
P. Salières
New Journal of Physics. 01/2008; 10:025028.
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[show abstract]
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ABSTRACT: It is now possible to generate optical pulses with a duration corresponding to only a few optical cycles of the electromagnetic
radiation in a wide spectral range. The generation of such short pulses is usually performed in two ways.
05/2007: pages 395-422;
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ABSTRACT: We theoretically study attosecond pulse production via high-harmonic generation using a driving laser pulse with a time-dependent ellipticity. The theoretical approach produces results that agree with our experimental data obtained using 35 fs driving laser pulses and is further used to study the generation of single attosecond pulses with shorter laser pulses. We find an equation for the duration of the temporal window created by the time-varying driving laser polarization in which high-harmonic emission can occur. We formulate the necessary requirements concerning the driving laser field in order to confine the high-harmonic emission in the form of a single attosecond pulse. Indeed, we show that using incident 12 fs laser pulses single attosecond pulses can be produced for certain carrier-envelope phase (CEP) values of the driving pulse. For 6 fs incident laser pulses, single attosecond pulses are produced for all values of the CEP (the intensity of the attosecond pulse still depends on the actual value of the CEP). If implemented with state-of-the-art 5 fs laser pulses, this technique can even lead to the production of sub-100 as pulses.
Journal of Physics B Atomic Molecular and Optical Physics 05/2005; 38(10):L161. · 1.88 Impact Factor
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ABSTRACT: We present time-resolved cross-correlation measurements of extreme ultraviolet (xuv) pulses generated as high-order harmonics of intense 35 fs pulses, using a short (12 fs) probe pulse. We modulate the ellipticity of the laser driving the generation process such that the polarization is linear for short times around the temporal peak of the pulse. Since harmonic generation is strongly suppressed for very small amounts of driving laser ellipticity, the emission of xuv radiation can therefore be confined to times much shorter than the laser pulse duration. In addition, our setup allows us to continuously confine the xuv emission as well as to determine its frequency sweep during the pulse.
Phys. Rev. A. 05/2004; 69(5).
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[show abstract]
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ABSTRACT: We have studied experimentally and theoretically high-order harmonic generation using a laser field with a time-dependent ellipticity. We show that the harmonic emission can be confined into a narrow temporal window, in which the fundamental polarization is quasi-linear. This allows a single attosecond pulse (200as) with a fundamental field obtained from 10fs pulse to be generated.
Applied Physics B 04/2004; 78(7):879-884. · 2.19 Impact Factor
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[show abstract]
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ABSTRACT: We investigate the temporal confinement of high order harmonic pulses generated by a femtosecond (fs) infrared (IR) pulse with a time varying polarization. We use a set of two birefringent quartz plates to modulate the IR polarization. It produces a short temporal gate of linear polarization where harmonics are efficiently generated during a small fraction of the IR pulse. By rotating one of the plates, the gate width can be continuously varied between 70fs down to 7fs. The XUV pulse duration is measured by cross-correlation with a probe IR pulse of 12fs. When the gate width is decreased, a clear temporal confinement of the XUV emission is observed through the cross correlation signal. This experiment is the first direct experimental evidence in the temporal domain that the polarization gating technique can be used to significantly shorten the harmonic pulse duration.
Applied Physics B 01/2004; 78(7):869-872. · 2.19 Impact Factor
