Anomalous absorption of very high-intensity laser pulses propagating through moderately dense plasma

The results of a systematic study of the propagation of very high-intensity laser pulses through slabs of plasma of several tens of microns are presented; One-dimensional and two-dimensional electron parametric instabilities are evidenced. They lead to a rapid longitudinal and transverse heating, and to filamentary structures which progressively merge. The heating results in highly energetic electrons with energy of several tens of MeV. Correlatively, a strong attenuation rate of the electromagnetic wave is observed.