%0 Journal Article
%A Krebs, Dietrich
%A Kerker, Fridtjof
%A Brockmueller, Xenia
%A Sahle, Christoph
%A Detlefs, Blanka
%A Huotari, Simo
%A Rohringer, Nina
%A Boemer, Christina
%T X-ray parametric down-conversion reveals EUV-polariton
%J Nature Communications
%V 16
%N 1
%@ 2041-1723
%C [London]
%I Springer Nature
%M PUBDB-2023-04098
%P 5383
%D 2025
%X Spontaneous parametric down-conversion (PDC) of photons is a gateway into the quantum realm – thoroughly studied in nonlinear optics and ubiquitously used to generate non-classical states of light. Extending PDC from the visible regime towards shorter wavelengths further enables microscopic resolution of electronic structure and quantum-enhanced X-ray detection, but remained challenging due to the process’ inherently low conversion rate. Here, we resolve the full signal cone of non-degenerate down-conversion at X-ray wavelengths and identify imprints of a polariton in the extreme ultraviolet (EUV) regime. We confirm our finding of the EUV-polariton with theoretical simulations and establish that our approach directly images the characteristic anti-crossing of polaritonic dispersion branches. This insight could open a pathway to explore strong-coupling phenomena of EUV-light-matter interaction.
%F PUB:(DE-HGF)16
%9 Journal Article
%R 10.1038/s41467-025-60845-8
%U https://bib-pubdb1.desy.de/record/587030