The interaction of ultrafast laser pulses with surfaces on the nanoscale paves the way for various innovative technologies in spectroscopy, photovoltaics, photocatalysis, or medicine, to mention only a few. The basic mechanisms, however, are still the subject of intense research. We take a closer look at this topic from different viewpoints. The first aspect is the enhancement of the efficiency of physical or chemical processes by producing local field maxima and resonances at top-down or bottom-up structured surfaces. A further aspect is the dynamic change of optical properties by inducing free carriers and plasmons. Last but not least, permanent nanostructures can be obtained as a result of nano-feedback and self-organization. In high-energy laser physics, all three aspects play a role at once. Therefore, particular attention will be paid to this emerging field.

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The self-organized formation of nanoscale laser-induced periodic surface structures (LIPSS) is still not fully understood with respect to the dynamics and interplay of contributing complex mechanisms. The transition from randomness to order and the specific role of nano-feedback are of fundamental interest because of their general aspects. In our study, the very first steps of the surface reconfiguration are demonstrated by analyzing the topology of evolving nano-crater maps. The evolution of spatial frequencies and directional arrangement indicate a feedback-driven adaptation of k-vectors to the required excitation conditions of elementary dipoles in the linearly polarized laser field. The time-dependent structure formation was studied by pump-probe diffraction and scattering experiments. The ratio of the contributions of characteristic light patterns enables plasmonic and non-plasmonic mechanisms to be distinguished, which subsequently act at distinctly different time scales. Recently developed multistage models for the dynamics of material modification are confirmed. The influence of accumulation effects is clearly demonstrated by characteristic changes in scattering and diffraction with an increasing number of preceding pulses. It is assumed that the thermal and plasmonic contributions to accumulation are coupled and thus generate spatially variable modifications.