Electron Acceleration and the Propagation of Ultrashort High-Intensity Laser Pulses in Plasmas

Reported are interactions of high-intensity laser pulses ( λ = 810 nm and I≤3×10¹⁸ W/cm²) with plasmas in a new parameter regime, in which the pulse duration ( τ = 29 fs) corresponds to 0.6–2.6 plasma periods. Relativistic filamentation is observed to cause laser-beam breakup and scattering of the beam out of the vacuum propagation angle. A beam of megaelectronvolt electrons with divergence angle as small as 1° is generated in the forward direction, which is correlated to the growth of the relativistic filamentation. Raman scattering, however, is found to be much less than previous long-pulse results.