Electron acceleration by few-cycle laser pulse with single-wavelength spot size

Generation of relativistic electrons from the interaction of a laser pulse with a high density plasma foil, accompanied by an underdense preplasma in front of it, has been studied with 2D particle-in-cell (PIC) simulations for pulse duration comparable to a single-cycle and for single-wavelength spot size. The primary mechanism responsible for electron acceleration is identified. Simulations show that the energy of the accelerated electrons has a maximum versus the pulse-duration for relativistic laser intensities. The most effective electron acceleration takes place when the preplasma scale length is comparable to the pulse-duration. Electron distribution functions have been found from PIC simulations. Their tails are well approximated by Maxwellian distributions with a hot temperature in the MeV range.