Field shaping and electron acceleration by center-depressed laser beams

Abstract

Technology that could shape laser beams either spatially or temporally would open up new research avenues. In this letter, a center-depressed laser beam is proposed for shaping the longitudinal electric force and the phase-velocity distribution, which play important roles in direct laser acceleration (also known as vacuum laser acceleration). The propagation of this laser beam is described analytically by the coherent superposition of two fundamental-mode Gaussian laser beams that differ in phase by π initially. A longitudinal electric force and a subluminous-wave phase-velocity region exist simultaneously in the center-depressed part of the laser beam. Three-dimensional particle simulations solving the relativistic Newton–Lorentz equation show that electrons injected into the center of the laser beam can be strongly accelerated.