Coherent Wake Emission of High-Order Harmonics from Overdense Plasmas

Quéré, F.; Thaury, C.; Monot, P.; Dobosz, S.; Martin, Ph.; Geindre, J. P.; Audebert, P.

doi:10.1103/physrevlett.96.125004

Cited by 330 publications

(253 citation statements)

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“…2) suggest that the CWE mechanism provides a dominant contribution in our experiments. In fact, CWE was found to show a well-defined cut-off that moves to higher energy for increasing density 15,18 (see Supplementary Information) as can be seen by comparing the spectra in Fig. 2a,c with those in Fig.…”

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confidence: 67%

“…One is based on a relativistic Doppler upshift of the laser light reflected off the oscillating plasma surface, acting as a relativistic oscillating mirror (ROM; refs 6,7). The other originates from currents excited by fast electrons in the density ramp of the plasma-vacuum interface leading to what has been dubbed coherent wake emission (CWE; refs 15,17). CWE is dominant at sub-or moderately relativistic intensities 17,18 for a L < 1, whereas ROM becomes more efficient for a L > 1 and completely takes over in the highly relativistic regime 12,19 , when a L 1.…”

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confidence: 99%

“…The fact that this value is very close to the laser pulse duration indicates that CWE scales nearly linearly with laser intensity, which agrees with the findings in ref. 15. To ascertain whether the XUV emission shows a sub-laser-cycle temporal structure indicative of attosecond synchronism among the filtered harmonics, we have performed a fine scan (delay step size 0.13 fs) over a delay interval of ∼4 laser cycles centred near the zero delay that yielded the maximum signal in the coarse scan.…”

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Attosecond phase locking of harmonics emitted from laser-produced plasmas

et al. 2008

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Laser-driven coherent extreme-ultraviolet (XUV) sources provide pulses lasting a few hundred attoseconds 1,2 , enabling real-time access to dynamic changes of the electronic structure of matter 3,4 , the fastest processes outside the atomic nucleus. These pulses, however, are typically rather weak. Exploiting the ultrahigh brilliance of accelerator-based XUV sources 5 and the unique time structure of their laser-based counterparts would open intriguing opportunities in ultrafast X-ray and high-field science, extending powerful nonlinear optical and pump-probe techniques towards X-ray frequencies, and paving the way towards unequalled radiation intensities. Relativistic laser-plasma interactions have been identified as a promising approach to achieve this goal 6-13 . Recent experiments confirmed that relativistically driven overdense plasmas are able to convert infrared laser light into harmonic XUV radiation with unparalleled efficiency, and demonstrated the scalability of the generation technique towards hard X-rays 14-19 . Here we show that the phases of the XUV harmonics emanating from the interaction processes are synchronized, and therefore enable attosecond temporal bunching. Along with the previous findings concerning energy conversion and recent advances in high-power laser technology, our experiment demonstrates the feasibility of confining unprecedented amounts of light energy to within less than one femtosecond.The nonlinear response of matter exposed to intense femtosecond laser pulses gives rise to the emission of highfrequency radiation at harmonics of the laser oscillation frequency. If the harmonics are phase-locked, their superposition results in a train of attosecond bursts 20 . The concept has been so far successfully implemented in atomic gases 21 , and culminated in isolated attosecond pulses by using few-cycle laser drivers 1,2 . The low generation efficiency of harmonic radiation from atoms has motivated research into alternative concepts. Dense, femtosecond-laser-produced plasmas hold promise of converting laser light into coherent harmonics with much higher efficiency and of exploiting much higher laser intensities, because the plasma medium-in contrast to the atomic emitters-imposes no restriction on the strength of the laser field driving the harmonics [6][7][8][9][10][11][12][13] . Recent experimental studies of harmonics produced from overdense plasmas impressively corroborate several theoretical predictions: the high conversion efficiency 19 , the favourable scalability of the generation technique towards high photon energies 14,16,19 and excellent divergence due to the spatial coherence of the generated harmonics 19,22 . Whether the high-order harmonics that are produced in overdense plasmas • gold-coated off-axis parabolic mirror with the same focal length as the laser focusing parabola. The recollimating mirror is mounted on a flipper stage for easy withdrawal, thus enabling the spectral characterization of the emitted XUV light. Thin metal filters (typically 150 nm Al, In or Sn)...

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Attosecond phase locking of harmonics emitted from laser-produced plasmas

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“…The harmonic emission emanating from the interaction of intense laser pulses with solid-density plasma is due to two main mechanisms. For relatively low laser intensities, the so-called coherent wake emission mechanism (CWE) dominates [11,12]. Under these circumstances, it has been recently demonstrated that the harmonic emission leads to temporal bunching with attosecond pulse durations [13,14].…”

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confidence: 99%

Multi-μJ harmonic emission energy from laser-driven plasma

et al. 2014

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“…This can be seen as the time-reverse of resonant absorption [22], where laser light is partially converted into collective electron oscillations in a gradient of plasma density (both effects correspond to linear mode conversion mechanisms [22,23]). This emission, known as coherent wake emission or CWE [24], consists of a sub-femtosecond burst of coherent radiation, superimposed with the laser light reflected at the plasma surface [25], with a spectrum extending into the extreme ultraviolet (XUV) up to ωmax = N solid /Nc ωL, emitted from the region of solid plasma density N solid (Fig. 1b).…”

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Attosecond control of collective electron motion in plasmas

et al. 2012

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Today, light fields of controlled and measured waveform can be used to guide electron motion in atoms and molecules with attosecond precision. Here, we demonstrate attosecond control of collective electron motion in plasmas driven by extreme intensity (≈ 10 18 W/cm 2 ) light fields.Controlled few-cycle near-infrared light waves are tightly focused at the interface between vacuum and a solid-density plasma, where they launch and guide subcycle motion of electrons from the plasma with characteristic energies in the multi-kiloelectronvolt range -two orders of magnitude more than what has been achieved so far in atoms and molecules. Basic spectroscopy of the coherent extreme ultraviolet radiation emerging from the light-plasma interaction allows us to probe this collective motion of charge with sub-100-attosecond resolution. This is an important step towards attosecond control of charge dynamics in laser-driven plasma experiments.Two major trends can nowadays be identified in the interaction of ultrashort laser pulses with matter. On the one hand, ultrahigh light intensities provided by multi-terawatt femtosecond lasers can be used to drive collective electron motion in plasmas up to the 0.1-1 gigaelectronvolt energy range [1], opening the way to very compact laser-based particle accelerators for nuclear and medical applications [2]. On the other hand, controlled few-cycle light waves can be used at moderate intensities to drive and probe the attosecond dynamics of few-electron motion in atoms [3,4,5,6], molecules [7,8] and condensed matter [9,10] -with typical energies * These authors contributed equally to this work. 1ranging between tens to a few hundred electronvolts [11]. Merging these two trends, i.e. using tailored waveforms of extreme intensity light to steer the collective motion of high-energy plasma electrons, will open brand new perspectives for imaging ultrafast charge dynamics during extreme intensity laser-plasma interactions. First experiments have already highlighted the need for waveform control when trying to reproducibly guide attosecond electronic processes in plasmas with intense few-cycle light fields [12]. For the first time, we use fully controlled few-cycle near-infrared (NIR) light fields of extreme intensity (10 18 W/cm 2 ) to reproducibly launch and probe collective electron motion at the interface between vacuum and a solid-density plasma with attosecond precision (Fig. 1a-b). Light-driven plasma mirrorsWhen an intense femtosecond laser pulse interacts with a solid, its rising edge strongly ionizes the surface atoms, creating a layer of plasma with near-solid electronic density (∼ 10 23 cm −3 ), which becomes highly reflectivea so-called plasma mirror -for light at wavelengths greater than a few tens of nanometers [13,14,15,16,17].During the interaction with the pulse, the plasma layer can only expand by a small fraction of the optical laser wavelength, λL, which leads to the formation of a very sharp interface with vacuum extending over a distance λL (Fig. 1b), typically of the order o...

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Coherent Wake Emission of High-Order Harmonics from Overdense Plasmas

Abstract: International audienc

Cited by 330 publications

References 16 publications

Attosecond phase locking of harmonics emitted from laser-produced plasmas

Attosecond phase locking of harmonics emitted from laser-produced plasmas

Multi-μJ harmonic emission energy from laser-driven plasma

Attosecond control of collective electron motion in plasmas

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