Electron vacuum acceleration by a tightly focused laser pulse

Interaction of a tightly focused relativistic short laser pulse with electrons beyond the paraxial approximation is studied by using the test particle approach and the Stratton-Chu integrals for the laser fields. The investigation addresses the regime where the focal spot size may be comparable to the laser wavelength. The mapping of near focal positions of the electrons to energy space allows for the study of important features of electron vacuum acceleration by a tightly focused laser pulse and to choose optimal parameters for acceleration. Two acceleration mechanisms have been observed and discussed. Directional properties of the accelerated electrons have been analyzed.