Sprecher
Beschreibung
We study both experimentally and numerically the emission of energetic electrons during the reflection of a relativistic few-cycle laser pulse ($1.4 \times 10^{19} \mathrm{~W/cm}^2$, 3.5 fs) on an overdense plasma. Two distinct acceleration regimes are identified (see Fig. 1), for which the electron ejection mechanisms are radically different. On the one hand, when the plasma-vacuum interface is sharp ("plasma mirror" regime), an attosecond electron bunch is emitted from the plasma at each laser optical cycle. These electrons can then be efficiently accelerated in vacuum by the reflected laser field. On the other hand, when the plasma scale length is larger (a few wavelengths), a different regime is identified in which electrons are accelerated by a laser wakefield in the near-critical density part of the plasma. Because of the resonant condition for plasma wave formation at such high densities, these electrons are only detected when the laser pulse duration is lower than 10 fs. This laser wakefield acceleration regime is characterized by a peculiar geometry where the plasma waves are rotated by the density gradient and the electrons are not emitted in the same direction as the driving laser pulse.
| Working group | Laser-driven electron acceleration |
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