Suprathermal and relativistic electrons produced in laser–plasma interaction at 0.26, 0.53, and 1.05 μm laser wavelength

Very energetic electrons produced in laser–plasma interactions at 0.26, 0.53, and 1.05 μm laser wavelength have been measured. The targets were 1.5 μm plastic foils and the laser intensity was around 1015 W/cm2. Detailed measurements of the electron distribution performed at a 0.26 μm laser wavelength exhibit an angular distribution strongly peaked along the laser axis at the highest energies (above 200 keV). Electrons up to 1.3 MeV have been observed in the 1.05 μm experiments. The hot temperatures inferred from the measured energy distributions are of the order of 100 keV in the 1.05 μm experiments, and 50 keV in the 0.53 μm/0.26 μm experiments. The experimental electron emission features are discussed with a special focus on the relation between the linear as well as the nonlinear electron plasma wave generation mechanisms and the maximum energy reached by an electron trapped in this wave.