Ultrafast target charging due to polarization triggered by laser-accelerated electrons

A significant step has been made towards understanding the physics of the transient surface current triggered by ejected electrons during the interaction of a short intense laser pulse with a high-conductivity target. Unlike the commonly discussed hypothesis of neutralization current generation as a result of the fast loss of hot electrons to the vacuum, the proposed mechanism is associated with excitation of the fast current by electric polarization due to transition radiation triggered by ejected electrons. We present a corresponding theoretical model and compare it with two simulation models using the finite-difference time-domain and particle-in-cell methods. Distinctive features of the proposed theory are clearly manifested in both of these models.