Matter and Radiation at Extremes, Volume. 8, Issue 6, 065601(2023)

Transition from backward to sideward stimulated Raman scattering with broadband lasers in plasmas

X. F. Li1...2,3,*, S. M. Weng1,2, P. Gibbon3,4, H. H. Ma1,2,5, S. H. Yew1,2, Z. Liu1,2, Y. Zhao6, M. Chen1,2, Z. M. Sheng1,2,5, and J. Zhang1,25 |Show fewer author(s)
Author Affiliations
  • 1Key Laboratory for Laser Plasmas (MoE), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
  • 2Collaborative Innovation Center of IFSA, Shanghai Jiao Tong University, Shanghai 200240, China
  • 3Institute for Advanced Simulation, Jülich Supercomputing Centre, Forschungszentrum Jülich, 52425 Jülich, Germany
  • 4Centre for Mathematical Plasma Astrophysics, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
  • 5Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai 200240, China
  • 6School of Science, Shenzhen Campus of Sun Yat-sen University, Shenzhen 518107, China
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    Figures & Tables(6)
    Linear theory of the SRS growth rate for a two-color laser. (a) Distribution of SRS growth rate Γ calculated according to Eq. (1) with a0 = 0.02 and n0 = 0.128nc. Here, Δk=(kx−k0)2+ky2−ksr and θ = 180° − arctan[ky/(kx − k0)]. The resonance point ksr is defined by the wave vector and frequency matching conditions of a monochromatic laser beam. (b) Region for Γ > 0 as a function of scattering angle (θ) for two individual laser beams at frequencies ω0 ± 0.5δω, denoted by the red and blue regions, respectively. Here, δω/ω0 = 1.2%, and a1,2 = 0.0141. The solid red and blue lines are the resonance points calculated using Eq. (3), and the width of each instability region is calculated using Eq. (2). (c) Growth rate as a function of scattering angle calculated using Eq. (5) for two-color laser light with δω/ω0 = 1.2%. (d) Coupling threshold angle θth as a function of the frequency difference δω between two individual monochromatic laser beams.
    SRS in the cases of monochromatic and two-color lasers with S-polarization. (a) Spatial distribution of Ex at 800T0. (b) Wave-vector distribution of Ex integrated over 0 ≤ t ≤ 1500T0 for monochromatic laser with S-polarization. Here, a0 = 0.02, w0 = 10λ, and n0 = 0.128nc. (c) and (d) Integrated wave-vector distributions for Ex (S-polarized laser) before 1500T0 in cases with two different laser frequencies, δω/ω0 = 0.6% and δω/ω0 = 1.2%, respectively. The amplitudes of the two beamlets are a1 = 0.0141 and a2 = 0.0141.
    SRS in the cases of monochromatic and two-color lasers with P-polarization: integrated wave-vector distributions for Ex (P-polarized laser) over 0 ≤ t ≤ 1500 T0 in the case of (a) a monochromatic laser and (b) a two-color laser with δω/ω0 = 1.2%.
    SRS generated by a broadband laser. (a) Integrated wave-vector distribution for Ex over 0 ≤ t ≤ 1500T0 for the case of an S-polarized broadband laser with Δω/ω0 = 2.6%. (b) Scattering angle θ with the maximum amplitude as a function of bandwidth. (c) Average reflectivity and transmittivity and (d) electron energy spectrum at 2500T0 for broadband lasers with different bandwidths and polarizations.
    Hot electron generation with a broadband laser: px–py phase distributions [(a) and (c)] and energy–angle distributions [(b) and (d)] of hot electrons with kinetic energy Ek > 30 keV at t = 2500 T0 obtained from 2D PIC simulation for the cases of monochromatic laser light [(a) and (b)] and broadband laser light with Δω/ω0 = 2.6% [(c) and (d)]. Here, φi = arctan(piy/pix), and i labels the individual electrons. The other simulation parameters were the same as those in Fig. 4(a).
    Model of a broadband laser. (a) The temporal evolution of the electric field obtained from Eq. (B3) for a broadband laser beam with a relative bandwidth Δω/ω0 = 4.0%. (b) Corresponding frequency spectrum and random phase spectrum obtained by Fourier transformation of the electric field in (a). (c) Spatial–temporal distribution of the electric field given by Eq. (B4) for a broadband laser beam with a relative bandwidth Δω/ω0 = 4.0% and a spot size w0 = 10λ.
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    X. F. Li, S. M. Weng, P. Gibbon, H. H. Ma, S. H. Yew, Z. Liu, Y. Zhao, M. Chen, Z. M. Sheng, J. Zhang. Transition from backward to sideward stimulated Raman scattering with broadband lasers in plasmas[J]. Matter and Radiation at Extremes, 2023, 8(6): 065601

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    Paper Information

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    Received: Mar. 31, 2023

    Accepted: Aug. 4, 2023

    Published Online: Mar. 21, 2024

    The Author Email:

    DOI:10.1063/5.0152668

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