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

Jian Gao, Boyuan Li, Feng Liu, Huaipeng Cai, Min Chen, Xiaohui Yuan, Xulei Ge, Liming Chen, Zhengming Sheng, Jie Zhang

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The influence of plasma density gradients on the harmonic generation process from relativistically oscillating mirror (ROM) is studied experimentally. It is observed that the harmonic intensities from orders of 21 st to 24 th first drop and then reach the maximum value with the increase of plasma scale length L. 2D particle-in-cell simulations are performed to investigate the intensities of high-order harmonics at different L values, which show that there are two optimal scale lengths Lopt for efficient ROM harmonic generation. The two optimal Lopt values are interpreted by a quasi-1D analytical model. By matching the potential energies provided by laser pulse and charge displacement in the plasma with an exponential distributed density profile, the model can quantitatively predict the optimal Lopt at the given laser incidence angle and intensity. Our work is beneficial for better understanding the role of L in ROM harmonic generation and the parameters affecting the optimal Lopt

Original languageEnglish
Article number103102
Number of pages6
JournalPhysics of Plasmas
Issue number10
Publication statusPublished - 1 Oct 2019


  • plasma density
  • relativistically oscillating mirror
  • harmonic generation

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