Double optimal density gradients for harmonic generation from relativistically oscillating plasma surfaces

Gao, Jianmei; Li, Boyuan; Liu, Feng; Cai, H.; Chen, Min; Yuan, Xiaohui; Ge, Xuan; Chen, Liming; Sheng, Zheng-Ming; Zhang, Jie

doi:10.1063/1.5097440

Cited by 11 publications

(10 citation statements)

References 33 publications

(43 reference statements)

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“…At the shortes gradients L − L 0 > λ 0 /50, the harmonic peaks are broad and their intensity quickly drops with increasing L, as expetected for CWE emission. At higher L, the harmonic peaks are remarkably narrower and their intensity goes through an optimum located at L − L 0 ≈ 0.06λ 0 , consistent with the theoretical expectations for relativistic SHHG emission as well as with earlier experimental observation with similar multi-cycle driver pulses [4,5,26,28]. We also remark that no harmonics are visible beyond the CWE-cutoff at 30 eV, even for softer gradients.…”

supporting

confidence: 91%

“…Furthermore, the intrinsic harmonic chirp and thus the spectral width of CWE-harmonic peaks increases with L [21,25]. In contrast, the optimal L for relativistic SHHG is longer and has been consistently found in single-shot experiments near a scale length L ≈ λ 0 /10 [4,5,26,28]. This can be shown to be consistent with particle-in-cell simulations, which often treat initially step-like plasma density profiles with variable peak density n. This adjusts the similarity parameter S = n/(n c a 0 ), which scales laser plasma-interaction in the relativistic regime [29].…”

mentioning

confidence: 90%

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High-Harmonic Generation and Correlated Electron Emission from Relativistic Plasma Mirrors at 1 kHz Repetition Rate

Haessler¹,

Ouillé²,

Kaur³

et al. 2020

Preprint

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We report evidence for the first generation of XUV spectra from relativistic surface high-harmonic generation (SHHG) on plasma mirrors at a kilohertz repetition rate, emitted simultaneously and correlated to the emission of energetic electrons. We present measurements of SHHG spectra and electron angular distributions as a function of the experimentally controlled plasma density gradient scale length L for three increasingly short and intense driving pulses: 24 fs (9 optical cycles) and a0 = 1.1, 9 fs (3.5 optical cycles) and a0 = 1.8, and finally 4 fs (1.7 optical cycles) and a0 ≈ 2.0. For all driver pulses, we observe relativistic SHHG in the range L ∈ [λ/25, λ/10], with an optimum gradient scale length of L ≈ λ/15.

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supporting

confidence: 91%

mentioning

confidence: 90%

High-Harmonic Generation and Correlated Electron Emission from Relativistic Plasma Mirrors at 1 kHz Repetition Rate

Haessler¹,

Ouillé²,

Kaur³

et al. 2020

Preprint

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“…The different plasma emission characteristics can be explained as follows. Highest conversion efficiency for second harmonic generation on solid density targets is achieved for plasma density surface-scalelengths shorter than the pump laser wavelength 37 – 39 . Depending on the pre-pulse timing, the pre-pulses utilized here generate a scalelength of multiple pump laser wavelengths.…”

Section: Plasma Emission and Spectral Filteringmentioning

confidence: 99%

Off-harmonic optical probing of high intensity laser plasma expansion dynamics in solid density hydrogen jets

Bernert

Assenbaum

Brack

et al. 2022

Sci Rep

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Due to the non-linear nature of relativistic laser induced plasma processes, the development of laser-plasma accelerators requires precise numerical modeling. Especially high intensity laser-solid interactions are sensitive to the temporal laser rising edge and the predictive capability of simulations suffers from incomplete information on the plasma state at the onset of the relativistic interaction. Experimental diagnostics utilizing ultra-fast optical backlighters can help to ease this challenge by providing temporally resolved inside into the plasma density evolution. We present the successful implementation of an off-harmonic optical probe laser setup to investigate the interaction of a high-intensity laser at $$5.4\times 10^{21}\,\hbox {W/cm}^{2}$$ 5.4 × 10 21 W/cm 2 peak intensity with a solid-density cylindrical cryogenic hydrogen jet target of $${5}\,{\upmu }\mathrm{m}$$ 5 μ m diameter as a target test bed. The temporal synchronization of pump and probe laser, spectral filtering and spectrally resolved data of the parasitic plasma self-emission are discussed. The probing technique mitigates detector saturation by self-emission and allowed to record a temporal scan of shadowgraphy data revealing details of the target ionization and expansion dynamics that were so far not accessible for the given laser intensity. Plasma expansion speeds of up to $$(2.3 \pm 0.4)\times 10^{7}\,\hbox {m/s}$$ ( 2.3 ± 0.4 ) × 10 7 m/s followed by full target transparency at $${1.4}\,{\mathrm{ps}}$$ 1.4 ps after the high intensity laser peak are observed. A three dimensional particle-in-cell simulation initiated with the diagnosed target pre-expansion at $${-0.2}\,{\mathrm{ps}}$$ - 0.2 ps and post processed by ray tracing simulations supports the experimental observations and demonstrates the capability of time resolved optical diagnostics to provide quantitative input and feedback to the numerical treatment within the time frame of the relativistic laser-plasma interaction.

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“…Here we propose a feasible scheme to realize the required pre-plasma truncation. The parameters of our scheme are based on the 200TW Ti:sapphire laser system at the Laboratory for Laser Plasmas of Shanghai Jiao Tong University [41]. As illustrated in Fig.…”

Section: Pre-plasma Truncation Realizationmentioning

confidence: 99%

“…The pre-plasma scale length is set to be L = 0.5λ 0 . This scale length is suitable for a fused silica glass irradiated by a laser with 10 −9 contrast [41], where the target surface would be preheated by the 10ps-ahead laser pedestal to a 10eV-level temperature. The 10 −9 contrast is currently a standard configuration for the commercial hundreds-of-terawatts laser chains.…”

Section: Pre-plasma Truncation Realizationmentioning

confidence: 99%

High-quality high-order harmonic generation through preplasma truncation

Liu

Chen

et al. 2019

Phys. Rev. E

Self Cite

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By introducing a pre-plasma truncation for the cases with initial pre-plasma scale length larger than 0.2λ, the efficiency of high-order harmonics generated from relativistic laser-solid interaction can be enhanced by more than one order of magnitude and the angular spread can be confined into near-diffraction-limited divergence. Numerical simulations show that the density truncation results in more compact oscillation of the surface electron sheet and the curvature of the reflection surface for driving laser is greatly reduced. This leads to an overall improvement in the harmonic beam quality. More importantly, the density truncation makes the harmonic generation weakly dependent on the pre-plasma scale length, which provides a way to relax the extremely high requirement on the temporal contrast of the driving laser pulse. A feasible scheme to realize the required pre-plasma truncation is also proposed and demonstrated by numerical simulations.

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Double optimal density gradients for harmonic generation from relativistically oscillating plasma surfaces

Cited by 11 publications

References 33 publications

High-Harmonic Generation and Correlated Electron Emission from Relativistic Plasma Mirrors at 1 kHz Repetition Rate

High-Harmonic Generation and Correlated Electron Emission from Relativistic Plasma Mirrors at 1 kHz Repetition Rate

Off-harmonic optical probing of high intensity laser plasma expansion dynamics in solid density hydrogen jets

High-quality high-order harmonic generation through preplasma truncation

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