Producing ultrashort, ultraintense plasma-based soft-x-ray laser pulses by high-harmonic seeding

Whittaker, D. S.; Fajardo, M.; Zeitoun, Ph.; Gautier, J.; Oliva, Eduardo; Sebban, S.; Velarde, P.

doi:10.1103/physreva.81.043836

Cited by 14 publications

(21 citation statements)

References 26 publications

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“…We assume only a Doppler profile. Neglecting collisional broadening reduces the profile width, artificially augmenting the gain and underestimating the saturation fluence [55], as shown by Koch and co-workers [56]. The Doppler effect is the principal mechanism of line broadening.…”

Section: Model To Obtain 2d Maps Of Atomic Datamentioning

confidence: 85%

Towards Tabletop X‐Ray Lasers

Zeitoun

Oliva

et al. 2014

Attosecond and XUV Physics

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Short pulses in the X-ray regime offer unique opportunities for the study of ultrafast processes in biology, chemistry and physics. The absorption of X-rays can occur with high spectral selectivity for direct chemical or physical analysis, the very low diffraction limit of X-rays is useful for imaging and physical analysis, and the short wavelength supports extremely short pulses in the attosecond (1 as D 10 18 s) and even zeptosecond (1 zs D 10 21 s) range [1,2]. Over the past few years, X-ray sources have reached higher and higher intensities by either reducing the pulse duration and the size of the focal spot, or by increasing the energy available in the generating process.The availability of X-ray pulses with ultrahigh intensity has opened new avenues for nonlinear physics and ultrafast imaging (see Chapter 17). A major concern in the field of ultrafast imaging is the danger of sample decomposition due to ionization by X-rays before the diffraction image (2D or 3D) is acquired. A theoretical study by Neutze et al. proposed that the ideal light source for this type of imaging should have about 10 12 photons in a fully coherent pulse with 5 fs duration or less, and with 12 keV photon energy [3]. For soft X-ray imaging (typically 30 eV to 1 keV photon energy), the parameters differ significantly. This energy range corresponds to wavelengths from 30 nm down to 1 nm, allowing experiments with diffraction-limited resolution of a few nanometers. Unlike the case discussed by Neutze, diffraction will not occur on molecular electrons but on nanoscale structures or sample structural variation. The bulk matter structure does not evolve as fast as molecular electrons, which often acquire relativistic speed. The relevant time scales are therefore defined by the speed of sound, typically 10 4 ms 1 for the density and temperature under consideration. To reach a target spatial resolution of 1 nm, the soft X-ray pulse duration should be on the order of 100 fs to prevent blurring during image exposure at the irradiation levels considered.Soft X-rays are often absorbed by the sample, reducing the signal flux at the detector. Hence the experiments require a high energy per pulse. To find an esAttosecond and XUV Physics, First Edition. Edited by Thomas Schultz and Marc Vrakking.

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Section: Model To Obtain 2d Maps Of Atomic Datamentioning

confidence: 85%

Towards Tabletop X‐Ray Lasers

Zeitoun

Oliva

et al. 2014

Attosecond and XUV Physics

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“…There is an increasing interest in better understanding the spectral behaviour of plasma-based collisional XUV lasers in the last years [1,2,3,4,5]. The main reason is that the shortest pulse duration that was reached until now is limited to ∼ 1 picosecond [6] by the extremely narrow bandwidth of these sources.…”

Section: Introductionmentioning

confidence: 99%

“…For numerous applications, like the production of plasma in the Warm Dense Matter regime (WDM) [7], one needs XUV lasers with a shorter pulse duration, namely in the subpicosecond or even in the femtosecond range. This could be obtained if the XUV laser is operated in an injection-seeded mode, using femtosecond high-order harmonic radiation as a seed [5,6], but only on condition that the bandwidth be enlarged by a factor ∼ 3 or larger. The ultimate duration τ FL of the output pulse of such an injection-seeded XUV laser is controlled by the spectral bandwidth of the plasma amplifier, through τ FL ∼ λ 2 ∆λ .…”

Section: Introductionmentioning

confidence: 99%

Line profiles of Ni-like collisional XUV laser amplifiers: Particle correlation effects

Calisti

Ferri

Mossé

et al. 2013

High Energy Density Physics

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We present a detailed analysis of the different processes that contribute to the spectral broadening of the Ni-like Ag XUV laser line, including the effects of particle correlations on the broadening due to the radiator motion (Doppler broadening). We consider two different regimes of collisional excitation pumping: the transient pumping for which ionic temperature is relatively low (the plasma coupling parameter is large), and the quasi steady-state pumping for which the ionic temperature is higher and the plasma coupling parameter is of the order of 1. In both cases, by using classical molecular dynamics simulation techniques, we show that ionic correlations actually modify the radiatormotion broadened profiles and cannot be neglected in evaluating the Doppler effect. The subsequent narrowing of the Doppler component is small compared to the overall linewidth, which includes the effect of homogeneous collisional broadening. However ionic correlations will also affect the amplification of the lasing line, especially when the laser enters the saturation regime, because it will lead to an homogenization of the spectral profile.

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“…It is worth noting that, due to the combination of fast gain regeneration and spectral stretching, the spectral components are amplified quasi-independently. Plasma XRLs, which are normally dominated by homogeneous broadening 11 , behave here like quasi-inhomogeneous lasers. Our preliminary calculations show that this characteristic opens the way to achieving 100 fs pulses by means of gain temporal shaping.…”

mentioning

confidence: 99%

“…Plasmas created by femtosecond 9 to picosecond 10 infrared lasers have been seeded, but continue to be limited by the generation of long (picosecond) and low-energy (1 |xj) pulses. Numerical studies have shown that these schemes could amplify the seed to generate pulses of up to 70 fs (ref 11), but with energy restricted to <40 |xj (ref. 12).…”

mentioning

confidence: 99%

A proposal for multi-tens of GW fully coherent femtosecond soft X-ray lasers

Oliva

Fajardo²,

et al. 2012

Nature Photon

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X-ray free-electron lasers 1,2 delivering up to 1 X 10 13 coherent photons in femtosecond pulses are bringing about a revolution in X-ray science 3 ' 5 . However, some plasma-based soft X-ray lasers 6 are attractive because they spontaneously emit an even higher number of photons (1 X 10 15 ), but these are emitted in incoherent and long (hundreds of picoseconds) pulses 7 as a consequence of the amplification of stochastic incoherent self-emission. Previous experimental attempts to seed such amplifiers with coherent femtosecond soft X-rays resulted in as yet unexplained weak amplification of the seed and strong amplification of incoherent spontaneous emission 8 . Using a time-dependent Maxwell-Bloch model describing the amplification of both coherent and incoherent soft X-rays in plasma, we explain the observed inefficiency and propose a new amplification scheme based on the seeding of stretched high harmonics using a transposition of chirped pulse amplification to soft X-rays. This scheme is able to deliver 5 X 10 14 fully coherent soft X-ray photons in 200 fs pulses and with a peak power of 20 GW.Over the past 10 years, the emergence of hard (A ~ 0.1 nm) and soft (A ~ 4-30 nm) X-ray free-electron lasers (FEL) with intensities rapidly increasing to 1 x 10 W cm has led to scientific breakthroughs in a diverse number of fields 3 " 5 . This race has led to renewed interest in a specific class of soft X-ray lasers (XRLs) that use a plasma amplifier created by the interaction of a nanosecond, high-energy laser with a solid target. These XRLs routinely produce an extreme number of photons per pulse 7 , up to 1 x 10 15 (that is, 10 mj), which compares favourably with soft X-ray FELs, which emit a maximum of 1 x 10 13 photons per pulse 1 ' 2 . However, because these plasma-based XRLs are running in amplification of spontaneous emission (ASE) mode, they demonstrate weak coherence and long pulse durations (100 ps). Seeding these plasmas, which naturally emit up to 10 mj, holds the greatest promise of producing fully coherent, femtosecond, multi-milljoule soft X-ray pulses. Such an experiment was carried out in 1995 8 , but this showed an as yet unexplained weak amplification of the seed (output, 100 nj) and strong amplification of the ASE (reaching several millijoules). Plasmas created by femtosecond 9 to picosecond 10 infrared lasers have been seeded, but continue to be limited by the generation of long (picosecond) and low-energy (1 |xj) pulses. Numerical studies have shown that these schemes could amplify the seed to generate pulses of up to 70 fs (ref 11), but with energy restricted to <40 |xj (ref. 12). It is only an indepth study of Ditmire's seminal experiment 8 that holds the key to unlocking the path towards millijoule, femtosecond soft X-ray lasers.The modelling parameters of our Maxwell-Bloch model 13 were adjusted on the basis of experiments 8 with a 200 fs, 0.5 nj, 21.2 nm seed, and plasma with an electron density of 4 x 10 20 cm 3 and temperature of 550 eV. In the absence of seed, gain peaks at 25 cm 1 were...

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Producing ultrashort, ultraintense plasma-based soft-x-ray laser pulses by high-harmonic seeding

Cited by 14 publications

References 26 publications

Towards Tabletop X‐Ray Lasers

Towards Tabletop X‐Ray Lasers

Line profiles of Ni-like collisional XUV laser amplifiers: Particle correlation effects

A proposal for multi-tens of GW fully coherent femtosecond soft X-ray lasers

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