Ultrashort laser pulse driven currents in conductors: physical mechanisms and time scales

The response of conduction band electrons to a local, pulse-like external excitation is investigated. The charge density wave packets that emerge as a consequence of the excitation leave the interaction region with a speed close to the initial state's band velocity, but there are also oscillations with essentially the same frequency as that of the laser field. As a good estimation, the excitation can also be considered as a localized, time-dependent ponderomotive potential, leading to slowly varying current oscillations. The role of all these effects are investigated for different electron energies, carrier frequencies and sizes of the interaction area.