Electron acceleration induced by interaction of two relativistic laser pulses in underdense plasmas

By using multidimensional particle-in-cell simulations, we demonstrate that the coherent interaction of two relativistic laser pulses in plasmas offers a degree of freedom for manipulating the electron acceleration process. It is shown that by adjusting the relative phase between two intense laser pulses, their interaction features in plasmas are well controlled, which subsequently induce different electron acceleration processes. In this case, the properties of the accelerated electron beam, including the directionality, the maximum energy, and the conversion efficiency, can be controlled though the manipulation of the energy redistribution of these intense laser pulses. In particular, compared to the cases with a single laser pulse or two out-of-phase laser pulses, two in-phase laser pulses fuse into a much stronger laser pulse, which significantly prolongs the electron acceleration length in plasmas and leads to the generation of energetic electron beam with much higher conversion efficiency.