Relativistic self-channeling of a picosecond laser pulse in a preformed plasma near critical density has been observed both experimentally and in 3D particle-in-cell simulations. Optical probing measurements indicate the formation of a single pulsating propagation channel, typically of about 5 mm in diameter. The computational results reveal the importance in the channel formation of relativistic electrons traveling with the light pulse and of the corresponding self-generated magnetic field.[S0031-9007(97)

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Relativistic electrons are produced, with energies up to 20 MeV, by the interaction of a high-intensity subpicosecond laser pulse (1 mm, 300 fs, 10 19 W͞cm 2 ) with an underdense plasma. Two suprathermal electron populations appear with temperatures of 1 and 3 MeV. In the same conditions, the laser beam transmission is increased up to 20%-30%. We observe both features along with the evidence of laser pulse channeling. A fluid model predicts a strong self-focusing of the pulse. Acceleration in the enhanced laser field seems the most likely mechanism leading to the second electron population.[S0031-9007(97)03893-3]

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