Table-top extreme ultraviolet second harmonic generation.

Helk, Tobias; Berger, Emma; Jamnuch, Sasawat; Hoffmann, Lars; Kabacinski, Adeline; Gautier, Julien; Tissandier, Fabien; Goddet, Jean-Philipe et al. · Sci Adv · 2021

basic_science · Level V

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Abstract

The lack of available table-top extreme ultraviolet (XUV) sources with high enough fluxes and coherence properties has limited the availability of nonlinear XUV and x-ray spectroscopies to free-electron lasers (FELs). Here, we demonstrate second harmonic generation (SHG) on a table-top XUV source by observing SHG near the Ti M<sub>2,3</sub> edge with a high-harmonic seeded soft x-ray laser. Furthermore, this experiment represents the first SHG experiment in the XUV. First-principles electronic structure calculations suggest the surface specificity and separate the observed signal into its resonant and nonresonant contributions. The realization of XUV-SHG on a table-top source opens up more accessible opportunities for the study of element-specific dynamics in multicomponent systems where surface, interfacial, and bulk-phase asymmetries play a driving role.