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arXiv · 1909.06068

THz generation from relativistic plasmas driven by near- to far-infrared laser pulses

J. Déchard·X. Davoine·L. Bergé
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Abstract

Terahertz pulse generation by ultra-intense two-color laser fields ionizing gases with near- to far-infrared carrier wavelength is studied from particle-in-cell (PIC) simulations. For long wavelength ($10.6\ μ$m) promoting a large ratio of electron density over critical, photoionization is shown to catastrophically enhance the plasma wakefield, causing a net downshift in the optical spectrum and exciting THz fields with tens of GV/m amplitude in the laser direction. This emission is accompanied by coherent transition radiation (CTR) of comparable amplitude due to wakefield-driven electron acceleration. We analytically evaluate the fraction of CTR energy up to 30 % of the total radiated emission including the particle self-field and numerically calibrate the efficiency of the matched blowout regime for electron densities varied over three orders of magnitude.

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J. Déchard, X. Davoine, L. Bergé. 2019-09-13. THz generation from relativistic plasmas driven by near- to far-infrared laser pulses. https://doi.org/10.1103/physrevlett.123.264801

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