Fig. 3
Results of the two-dimensional particle-in-cell simulation. The intensity envelope of the diverging amplified pulse is shown at three time-steps in the simulation, at a 0 ps, b 11.2 ps and c 22.4 ps. The plasma was uniform with density 1019 cm−3 and the pump amplitude (visible on this colour scale only at the first time-step) decreased a0 ∝ 1/\(\sqrt {t - t_{\mathrm {f}}}\). The pulse propagates towards the right and it has been smoothed on a wavelength scale using a Gaussian filter
