Properties of electron acceleration by a circularly polarized laser in vacuum

The dynamic characteristics of an electron accelerated by ultraintense circularly polarized laser pulses in vacuum following the capture and acceleration scenario were studied. Comparing them with that from the use of linearly polarized laser pulses, we found (i) that the acceleration channel is wider, leading to greater acceleration efficiency, and (ii) that the maximum energy gains rise much more slowly as the laser intensity increases. This slow rise is caused by the magnetic-field force, which weakens the longitudinal acceleration force at higher laser intensity.