Abstract.  The present contribution is intended as a study on novel aspects of relativistic plasma physics and superrelativistic electrodynamics. Nowadays lasers come close to flux densities of 10²³ Wcm^-2, corresponding to electric field amplitudes of 10¹⁵ Vm^-1. This opens new possibilities to investigate radiation-matter interaction in a novel dynamic regime. When interacting with bulk matter the most prominent feature is the generation of energetic particles and, in concomitance, the disposal of new sources of intense soft and hard photon beams.

Traditional linear and nonlinear optics at high intensities is characterized by the regular motion of electrons in the laser field. At superhigh intensities the motion of the single electron in the laser field, even if assumed perfectly regular, assumes aspects of chaotic dynamics. At first glance surprising, it happens mainly for two reasons: (1) in bulk matter radiation pressure and the relativistic electron motion generate particle jets which in turn excite secular electric and magnetic fields that superpose to the laser field; (2) in dilute matter the electron interacts with its own radiation field with the consequence that at extreme intensities its natural oscillatory motion undergoes appreciable modifications.

In a first step the evolution towards chaos in representative regular fields is shown. Particular attention is then focused onto the role of anharmonic resonanes for the generation of the hot electron component that is present in all interaction experiments with solid and liquid targets as well as with clusters and droplets. Numerous models have been proposed during the last two decades to explain the origin of these fast electron jets; nevertheless the underlying physical mechanism is not well understood. Here an attempt is made that may shed new light on the phenomenon. In the context recently obtained results on relativistic transparency of dense matter under circular and linear polarization are also discussed.

The second part of the presentation is dedicated to single electron motion in superstrong laser fields. It is intended as an introduction to advanced studies (see e. g. H. Ruhl) of classical and quantum problems connected with the electron dynamics, particle acceleration and radiation “cooling” in its own radiation field. Thereby some discussion will be dedicated to the familiar Abraham-Lorentz-Dirac equation and special solutions of it.