Since the invention of the laser in 1960, our ability to harness light for practical applications has increased exponentially. For many years, however, interest in the spatial profile of laser beams was dominated by the quest for smoother, cleaner Gaussian beams—free of undesired spatial inhomogeneities—because they can be focused to a minimum-size spot. By contrast, advanced applications benefit from non-uniform intensity, phase, or polarization distributions. Paradigmatic examples include optical tweezers and adaptive-wavefront optics. Control of light in its transverse dimension has therefore spurred the development of techniques for structuring, sculpting, or tailoring beams. The general term structured light refers to beams with non-homogeneous, non-trivial distributions of intensity, phase and/or polarization in the plane transverse to propagation.
Recent advances in structured laser pulses in the ultrafast regime—down to femtoseconds (1 fs = 10⁻¹⁵ s)—together with improved understanding of their nonlinear interaction with solids and gases, have enabled the up-conversion of structured light into the extreme-ultraviolet (EUV), an attractive domain for manipulating magnetic and chiral systems on ultrafast timescales. Reaching this milestone was non-trivial: most generation techniques are wavelength-dependent and inefficient at high frequencies. Consequently, generating structured light in these extreme regimes must be accompanied by theoretical efforts to understand topology and the conservation rules governing spin–orbit exchange between light and matter.
ATTOSTRUCTURA aims to develop novel ultrafast structured-light tools and to explore their application in ultrafast magnetism. Thanks to high-harmonic generation (HHG), it is now possible to produce attosecond pulses structured in polarization and orbital angular momentum (OAM). We seek to push these capabilities to their limits, devising strategies for attosecond/X-ray sources with controlled angular momentum. We also design new HHG schemes in atomic and solid systems where structured pulses grant access to previously unexplored ultrafast phenomena. Finally, we explore scenarios of ultrafast magnetism that leverage structured laser pulses.
Conclusions of the action. We have established a coherent theoretical, computational, and experimental pathway for structured-light–driven HHG and its applications. In particular, we developed new theoretical frameworks for simulating HHG with structured beams in gaseous and solid targets; generated new forms of ultrafast, high-frequency structured light—such as vector–vortex beams, spatiotemporal EUV vortices, attosecond STOVs (spatiotemporal optical vortices), and attosecond skyrmions; pioneered the use of structured light at the nanoscale to enhance attosecond pulse sources (e.g. frequency content and peak intensity); and established a practical route to high-frequency structured-light generation in solids via HHG. These advances laid the groundwork for proposed attomagnetism experiments based on isolated magnetic pulses with controlled polarization. We uncovered a scenario in which nonlinear magnetization switching can be driven by circularly polarized magnetic fields. Finally, we developed the multi-platform HHGstudio app to support researchers and experimentalists in modeling HHG and proposing new schemes in attosecond science.
