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Published online by Cambridge University Press: 13 July 2015
In this study, non-paraxial nonlinear propagation of a relativistic laser pulse with linear and circular polarization in a preformed plasma channel having a parabolic density profile is investigated. The circular laser spot size variation in the absence/presence of an external longitudinal magnetic field is separately analysed and the results are compared. The amplitude of oscillation is decreased in the relativistic case, but it is changed in the presence of an external field. The right-turn circular pulse behaviour is completely opposite to that of the left-turn circular pulse in the presence of an external field, because the right-turn pulse is focused later than the left-turn pulse. The effect of nonlinearities on oscillations of spot size is analysed and the nonlinear critical channel depth required for propagation of a self-trapped laser pulse is evaluated. The laser field amplitude is derived for a matched pulse and it is shown that the group velocity dispersion effect causes broadening of the pulse length.