Wake field excitation and electron acceleration by triangular and sawtooth laser pulses in a plasma: an analytical approach

Abstract

The amplitude of wake fields generated by the finite-width laser pulse propagating in an underdense plasma are determined using weakly nonlinear equations (n′e≪n0) for triangular (TR) and two types of sawtooth (SD and SI, defined in section 2) pulses by making the pulse duration the same as the electron plasma period. In addition to density perturbations ne′, the potential ϕ and the wake field Ez behind the laser pulses, the expression for the change in relativistic factor γ or energy gain for an electron is obtained and discussed for all these types of laser pulses under the effect of laser frequency f, pulse duration τ (corresponding to plasma density n0) and laser intensity I0. The TR pulse is found to be most significant as in this case the electrons can be accelerated up to hundreds of MeV (471.6 MeV) when τ = 6 ps, I0 = 1.0×1012 W m−2 and f = 282 THz (corresponding to Nd:YAG laser of wavelength 1.064 μm); even more acceleration is possible with prudently selected parameters.