Concerning laser-driven electron acceleration in vacuum, a comparison was made between using circularly polarized (CP) laser field and linearly polarized (LP) field. It has been found that the main advantage for using CP field is that its acceleration channel occupies relatively larger phase space, which can give rise to greater acceleration efficiency. This feature chiefly comes from the difference in the distribution of the longitudinal electric components of these two kinds of fields. One of the disadvantages with CP field is the “energy saturation” phenomenon as the laser intensity is sufficiently high, resulting from the enhanced Lorentz force component in CP field. Physical explanations of these characteristics are addressed as well.
