• High Power Laser Science and Engineering
  • Vol. 8, Issue 2, 02000e21 (2020)
Yao Zhao1、*, Suming Weng2, Zhengming Sheng3, and Jianqiang Zhu4
Author Affiliations
  • 1Key Laboratory of High Power Laser and Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai201800, China
  • 2Key Laboratory for Laser Plasmas (MoE), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai200240, China
  • 3Key Laboratory for Laser Plasmas (MoE), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai200240, China
  • 4Key Laboratory of High Power Laser and Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai201800, China
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    DOI: 10.1017/hpl.2020.22 Cite this Article Set citation alerts
    Yao Zhao, Suming Weng, Zhengming Sheng, Jianqiang Zhu. Stimulated Raman scattering in a non-eigenmode regime[J]. High Power Laser Science and Engineering, 2020, 8(2): 02000e21 Copy Citation Text show less

    Abstract

    Stimulated Raman scattering (SRS) in plasma in a non-eigenmode regime is studied theoretically and numerically. Different from normal SRS with the eigen electrostatic mode excited, the non-eigenmode SRS is developed at plasma density $n_{e}>0.25n_{c}$ when the laser amplitude is larger than a certain threshold. To satisfy the phase-matching conditions of frequency and wavenumber, the excited electrostatic mode has a constant frequency around half of the incident light frequency $\unicode[STIX]{x1D714}_{0}/2$, which is no longer the eigenmode of electron plasma wave $\unicode[STIX]{x1D714}_{pe}$. Both the scattered light and the electrostatic wave are trapped in plasma with their group velocities being zero. Super-hot electrons are produced by the non-eigen electrostatic wave. Our theoretical model is validated by particle-in-cell simulations. The SRS driven in this non-eigenmode regime is an important laser energy loss mechanism in the laser plasma interactions as long as the laser intensity is higher than $10^{15}~\text{W}/\text{cm}^{2}$.
    $$\begin{eqnarray}\unicode[STIX]{x1D714}_{e}^{2}-\unicode[STIX]{x1D714}_{pe}^{2}=\frac{\unicode[STIX]{x1D714}_{pe}^{2}k_{e}^{2}c^{2}a_{0}^{2}}{4}\left(\frac{1}{D_{e+}}+\frac{1}{D_{e-}}\right),\end{eqnarray}$$(1)

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    $$\begin{eqnarray}\displaystyle & & \displaystyle (\unicode[STIX]{x1D714}_{0}\unicode[STIX]{x1D714}_{ei}-2\unicode[STIX]{x1D714}_{ei}\unicode[STIX]{x1D714}_{er})(\unicode[STIX]{x1D714}_{ei}^{2}-\unicode[STIX]{x1D714}_{er}^{2}-2\unicode[STIX]{x1D714}_{0}\unicode[STIX]{x1D714}_{er}+3\unicode[STIX]{x1D714}_{0}^{2}\nonumber\\ \displaystyle & & \displaystyle \quad -\,3\unicode[STIX]{x1D714}_{pe}^{2} )(\unicode[STIX]{x1D714}_{er}^{2}+\unicode[STIX]{x1D714}_{ei}^{2}-\unicode[STIX]{x1D714}_{er}\unicode[STIX]{x1D714}_{0}-\unicode[STIX]{x1D714}_{pe}^{2})=0.\end{eqnarray}$$(2)

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    $$\begin{eqnarray}\unicode[STIX]{x1D714}_{ei}=\frac{1}{2}\sqrt{4\unicode[STIX]{x1D714}_{pe}(\unicode[STIX]{x1D714}_{0}-\unicode[STIX]{x1D714}_{pe})+\unicode[STIX]{x1D714}_{pe}^{2}a_{0}^{2}k_{0}^{2}c^{2}/\unicode[STIX]{x1D714}_{0}^{2}-\unicode[STIX]{x1D714}_{0}^{2}}.\end{eqnarray}$$(3)

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    $$\begin{eqnarray}a_{th-n}\gtrsim \frac{\unicode[STIX]{x1D714}_{0}\sqrt{\unicode[STIX]{x1D714}_{0}^{2}+4(\unicode[STIX]{x1D714}_{pe}^{2}-\unicode[STIX]{x1D714}_{pe}\unicode[STIX]{x1D714}_{0})}}{\unicode[STIX]{x1D714}_{pe}k_{0}c}.\end{eqnarray}$$(4)

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    $$\begin{eqnarray}\unicode[STIX]{x1D714}_{e}^{2}-\unicode[STIX]{x1D714}_{L}^{2}=\frac{\unicode[STIX]{x1D714}_{pe}^{\prime 2}k_{e}^{2}c^{2}a_{0}^{2}}{4\unicode[STIX]{x1D6FE}^{2}}\left(\frac{1}{D_{e+}}+\frac{1}{D_{e-}}\right),\end{eqnarray}$$(5)

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    $$\begin{eqnarray}\displaystyle & & \displaystyle (\unicode[STIX]{x1D714}_{0}\unicode[STIX]{x1D714}_{ei}-2\unicode[STIX]{x1D714}_{ei}\unicode[STIX]{x1D714}_{er})(\unicode[STIX]{x1D714}_{ei}^{2}-\unicode[STIX]{x1D714}_{er}^{2}-2\unicode[STIX]{x1D714}_{0}\unicode[STIX]{x1D714}_{er}+3\unicode[STIX]{x1D714}_{0}^{2}\nonumber\\ \displaystyle & & \displaystyle \quad -\,3\unicode[STIX]{x1D714}_{pe}^{\prime 2} )(\unicode[STIX]{x1D714}_{er}^{2}+\unicode[STIX]{x1D714}_{ei}^{2}-\unicode[STIX]{x1D714}_{er}\unicode[STIX]{x1D714}_{0}-\unicode[STIX]{x1D714}_{L}^{2})=0.\end{eqnarray}$$(6)

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    $$\begin{eqnarray}\unicode[STIX]{x1D714}_{er}=\frac{\unicode[STIX]{x1D714}_{0}}{2}=\frac{1}{2}\sqrt{k_{e}^{2}c^{2}+\unicode[STIX]{x1D714}_{pe}^{2}}.\end{eqnarray}$$(7)

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    $$\begin{eqnarray}\unicode[STIX]{x1D714}_{s}^{2}-k_{s}^{2}c^{2}-\unicode[STIX]{x1D714}_{pe}^{2}=D_{s+}+D_{s-},\end{eqnarray}$$(8)

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    Yao Zhao, Suming Weng, Zhengming Sheng, Jianqiang Zhu. Stimulated Raman scattering in a non-eigenmode regime[J]. High Power Laser Science and Engineering, 2020, 8(2): 02000e21
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