Electron-Nanobunch-Width-Dominated Spectral Power Law for Relativistic Harmonic Generation from Ultrathin Foils

Edwards, Matthew R.; Fasano, Nicholas; Mikhailova, Julia M.

doi:10.1103/physrevlett.124.185004

Cited by 13 publications

(2 citation statements)

References 49 publications

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“…However, due to the electron bunch has a Heaviside step function distribution, it has a smaller cutoff ω h = (T 0 /2τ a )ω 0 = 25ω 0 , where τ a is calculated in the advanced time (t a = t + x/c) frame [34]. After the ω h , the spectrum then has a steeper slope p = −10/3 [35].…”

Section: Cse In Transition Directionmentioning

confidence: 99%

The effects of plasma density-gradient on laser-driven transmitted emission

Jiang

Chen

Cao

et al. 2020

Plasma Phys. Control. Fusion

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High-order harmonic generation provides an opportunity for generating intense extreme ultraviolet attosecond pulses, which is useful to explore the property of materials. Transmitted radiation emitted by an ultrathin target illuminated by intense lasers is a promising way to generate such pulses. We show that the preplasma density gradient has an important influence on the transmitted radiation. An optimal scale length exists to support ultrathin nanobunches to generate coherent synchrotron emission and thus enormously enhance the radiation. Particle in cell simulations suggest that the optimal scale length depends on the laser intensity.

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Section: Cse In Transition Directionmentioning

confidence: 99%

The effects of plasma density-gradient on laser-driven transmitted emission

Jiang

Chen

Cao

et al. 2020

Plasma Phys. Control. Fusion

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show abstract

“…Compared to gas-based sources, plasma could support far higher laser intensities and offer a route to large-energy attosecond pulses. Hitherto, several radiation mechanisms of high-order harmonic generation (HHG) have been theoretically and experimentally distinguished, including coherent wake emission (CWE) [12,13], relativistically oscillating mirror (ROM) [1][2][3][4][5][6][7] and coherent synchrotron emission (CSE) [9,[14][15][16][17][18][19].…”

mentioning

confidence: 99%

Synergistic Longitudinal Acceleration and Transverse Oscillation in High-order Harmonic Generation

Shen,

Pukhov,

Qiao

2020

Preprint

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We propose and demonstrate that relativistic harmonics with a slowly decaying power law are generated from a femtosecond lase pulse incident parallel to a micro-scale overdense plasma. It is shown that due to the excitation of a strong surface wave, dense electron nanobunches are continuously accelerated forward while oscillating in the transverse laser field. Even around the stationary phase point, relativistic gamma factors of the nanobunches increase considerably, leading to a much stronger attosecond burst, compared to the case with constant gamma. Our two-dimensional particle-in-cell simulations and analytical theory show that this synergistic function promises a power-law harmonic spectrum In/I0 = n −1 . This is much flatter than the other well-known radiation mechanisms and paves the way to unprecedentedly large energy attosecond pulses.

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The X-Ray Emission Effectiveness of Plasma Mirrors: Reexamining Power-Law Scaling for Relativistic High-Order Harmonic Generation

Edwards

Mikhailova

2020

Sci Rep

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Ultrashort pulsed lasers provide uniquely detailed access to the ultrafast dynamics of physical, chemical, and biological systems, but only a handful of wavelengths are directly produced by solid-state lasers, necessitating efficient high-power frequency conversion. Relativistic plasma mirrors generate broadband power-law spectra, that may span the gap between petawatt-class infrared laser facilities and x-ray free-electron lasers; despite substantial theoretical work the ultimate efficiency of this relativistic high-order-harmonic generation remains unclear. We show that the coherent radiation emitted by plasma mirrors follows a power-law distribution of energy over frequency with an exponent that, even in the ultrarelativistic limit, strongly depends on the ratio of laser intensity to plasma density and exceeds the frequently quoted value of −8/3 over a wide range of parameters. The coherent synchrotron emission model, when adequately corrected for the finite width of emitting electron bunches, is not just valid for p-polarized light and thin foil targets, but generally describes relativistic harmonic generation, including at normal incidence and with finite-gradient plasmas. Our numerical results support the ω−4/3 scaling of the synchrotron emission model as a limiting efficiency of the process under most conditions. The highest frequencies that can be generated with this scaling are usually restricted by the width of the emitting electron bunch rather than the Lorentz factor of the fastest electrons. The theoretical scaling relations developed here suggest, for example, that with a 20-PW 800-nm driving laser, 1 TW/harmonic can be produced for 1-keV photons.

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Electron-Nanobunch-Width-Dominated Spectral Power Law for Relativistic Harmonic Generation from Ultrathin Foils

Cited by 13 publications

References 49 publications

The effects of plasma density-gradient on laser-driven transmitted emission

The effects of plasma density-gradient on laser-driven transmitted emission

Synergistic Longitudinal Acceleration and Transverse Oscillation in High-order Harmonic Generation

The X-Ray Emission Effectiveness of Plasma Mirrors: Reexamining Power-Law Scaling for Relativistic High-Order Harmonic Generation

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