Dispersion in laser-driven relativistic quantum systems

The wave packet dynamics of electrons driven by strong laser fields is examined with the objective to both describe and manipulate the spreading dynamics. Having established analytical methods based on either classical or quantum mechanics, the quantum approach is first applied to free, laser-driven electrons. Intuitive results are found for both the relativistic and the nonrelativistic regime beyond the dipole approximation. In order to generalize the concept of recollisions to relativistic energies where magnetic field effects are important, the electron dynamics in standing laser fields with linear and circular polarization are analyzed and compared. Furthermore, a novel scheme of two consecutive laser pulses is introduced, which allows for recollisions with the maximum electron energy accessible in propagating laser fields. In this scheme, the Lorentz drift is employed both to separate electrons from atoms or molecules and to drive them back for recollisions. Aiming to increase the reaction probabilities of recollisions, two methods to inverse wave packet spreading are introduced. Both approaches, i.e. refocusing with a harmonic potential and magnetic refocusing, can be implemented in the scheme with two consecutive laser pulses to enable effective, relativistic recollisions