Analysis of electron acceleration in a vacuumbeat wave

Abstract

We present an exact analytic investigation of the electrondynamics in the field of two linearly polarized interferingcopropagating laser beams of different frequencies, arbitraryintensities, and arbitrary relative polarizations. In one part ofthe paper, the laser fields are modelled byplane waves and in another part the fields are allowed to haveone-dimensional sin2 pulse shapes which model focusing in thepropagation direction. The general situation in which the electron isinjected at an angle with the common direction of wave propagation isconsidered throughout. A cycle-by-cycle analysis of the electronmotion, and its momentum and energy exchange with the laser fields isconducted. It is found that an electron may be accelerated, evenfrom rest, to GeV energies over short distances using present-daylaser field intensities. This leads, in principle, to energygradients in the TeV m-1 range. The trajectory calculations alsoshow clearly that the electron gets scattered away from itsinitial direction of motion during interaction with the laser fields. Thetransverse as well as longitudinal motions may be followedexactly using our equations, and predictions could thus be madeconcerning where the electron should, in principle, be ejected inorder for it to emerge with a particular energy gain.