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arXiv · 1709.04639

Sequential terahertz pulse generation by photoionization and coherent transition radiation in underdense relativistic plasmas

J. Déchard·A. Debayle·X. Davoine·L. Gremillet·L. Bergé
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Abstract

Terahertz (THz) emission by two-color, ultrashort optical pulses interacting with underdense helium gases at ultrahigh intensities ($> 10^{19}\,\mathrm{W/cm}^2$) is investigated by means of 3D particle-in-cell simulations. The THz field is shown to be produced by two mechanisms occurring sequentially, namely, photoionization-induced radiation (PIR) by the two-color pulse and coherent transition radiation (CTR) by the wakefield-accelerated electrons escaping the plasma. For plasmas of atomic densities $> 10^{17}\,\mathrm{cm}^{-3}$, CTR proves to be the dominant process, providing THz bursts with field strength as high as $100\,\mathrm{GV/m}$ and energy in excess of $1\,\mathrm{mJ}$. Analytical models are developed for both the PIR and CTR processes, which correctly reproduce the simulation data.

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J. Déchard, A. Debayle, X. Davoine, L. Gremillet, L. Bergé. 2017-09-14. Sequential terahertz pulse generation by photoionization and coherent transition radiation in underdense relativistic plasmas. https://doi.org/10.1103/physrevlett.120.144801

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