Extreme regimes of structured light-matter interaction

First, we investigate the interaction of laser pulses with structured matter: arrays of aligned nanowires. This leads to high absorption, volumetric heating and matter states with ultra-high energy density. Second, we study the interaction of electrons with different circularly polarized twisted light pulses in the framework of relativistic particle-in-cell simulations in a fully three-dimensional geometry. The interaction is very sensitive to both the twisted light mode and to the handedness of the laser. It is shown that the twisted light pulse can be used to excite spatially structured electron beams. Depending on the chosen laser parameters, it becomes possible to drive a train of azimuthally-symmetric electron bunches or to excite a discrete number of helical electron beams. The emerging electron patterns are characterized by full width at half maximum durations of the order of a few hundred attoseconds. In addition, it is reported on an efficient transfer of angular momentum from the twisted light field to the particles. Third, we consider a few options to access the ultimate QED limit of matter in the strong electro-magnetic field, when \xi \alpha^2/3 > 1, where \alpha=1/137 is the fine-structure constant and \xi is the nonlinear quantum parameter. This regime of fully non-perturbative QED has long been assumed to be not accessible experimentally. Yet, the progress in laser technology and particle accelerators may bring this regime within experimental reach.