Attosecond control of collective electron motion in plasmas

Abstract

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...

Lightwave control of attosecond pulse emission from plasma mirrors

“…Figure 2 shows the near-linear drift of the harmonic peaks in the spectra (integrated over 300 laser shots) as the CEP is swept through. The very strong dependence of the shape of the EUV spectrum with slight changes of the CEP (250 mrad) proves that we can effectively control the plasma mirror dynamics with sub-200 as resolution [13].…”

“…2b) as well as those generated by a comprehensive 2-dimensional "Particles In Cell" simulation (see Fig. 2c and supplementary information of [13]). …”

“…In order to picture lightwave-driven plasma electron dynamics, we developed a simple onedimension model (see details in supplementary information of [13]) that solves the relativistic equation of motion of the electronic charges submitted to both laser and plasma electric fields and gives access to the temporal and spectral properties of the generated attosecond pulse train. The results of the model are in excellent agreement with the recorded CEP-dependent harmonic spectra (see Fig.…”

MAKING OPTICAL WAVES, TRACING ELECTRONS IN REAL-TIME: THE ONSET OF THE ATTOSECOND REALM (Invited Review)

“…The cosine wave gives rise to a smooth spectrum in the cutoff range, suggesting emission in a single burst of potentially sub-fs duration, whereas the appearance of modulation for the sine wave suggests that that the emission is distributed in two bursts half a cycle apart. complex molecules [33,34] or towards the sub-cycle manipulation of EUV generation in strongly driven surface plasmas [35] and the photoemission from metal nanotips [36].…”

Solid-state light phase detector

“…π ω of the waveform, CE ϕ affects the evolution of nonlinear electron phenomena driven by ( ) F t , including high-order harmonic generation [5,6], ionization of atoms and molecules [7][8][9], interaction with plasmas [10], as well as photoemission from metals [11,12] and nanoparticles [13]. Attosecond control over these processes calls for control and full characterization of the applied electric field ( ) F t .…”