Comment on “Dynamics of an electron driven by relativistically intense laser radiation” [Phys. Plasmas 15, 023104 (2008)]

Abstract

Galkin et al. ͓Phys. Plasmas 15, 023104 ͑2008͔͒ presented the comparison of the electron dynamics in the cases of the linear and circular polarizations of the optical fields. They assume that the longitudinal component of the laser field can be neglected in the case of longitudinal displacement less than the Rayleigh range. In this comment, we point out that the longitudinal component must be considered for the minimum spot size less than 10 times wavelength for linearly polarized laser pulse and for the minimum spot size less than 15 times wavelength for circularly polarized laser pulse.