Mainz 2026 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 41: Interaction with Strong or Short Laser Pulses II
A 41.1: Hauptvortrag
Freitag, 6. März 2026, 11:00–11:30, N 2
State-resolved femtosecond phase control in dense-gas laser-atom interaction enabled by XUV interferometry — •Lina Hedewig1,2, Carlo Kleine1, Yu He1, Felix Wieder1,2, Christian Ott1,2, and Thomas Pfeifer1,2 — 1Max-Planck-Institut für Kernphysik, Heidelberg, Germany — 2Ruprecht-Karls-Universität Heidelberg, Germany
We perform an interferometric measurement of an extreme ultraviolet (XUV) pulse passing through an optically dense gas-phase target. Utilizing the interaction with strong and narrow atomic resonances, we demonstrate the femtosecond phase control of the resonant XUV pulse propagation by means of a time-delayed intense near-infrared (NIR) laser pulse. To this end, the concept of spectral interferometry is transferred to the extreme ultraviolet in combination with a computational phase stabilization during post–processing [1]. By doing so, we obtain direct access to the amplitude and phase of the transmitted pulse and hence to the ultrafast dynamics in the target gas.
We benchmark our measurement approach with the singly excited 1s4p Rydberg state of helium to directly reconstruct the temporal structure of the transmitted XUV pulse beyond the single-atom response. An NIR-intensity-controlled variable phase step between 0 and 2 rad is measured on the XUV pulse after passage through the medium, originating from laser-induced transient Stark shifts. [2]
[1] L. Hedewig et al., Opt. Express 33, 48151-48159 (2025)
[2] L. Hedewig et al., Opt. Lett. 50, 3006-3009 (2025)
Keywords: XUV spectral interferometry; dipole phase reconstruction; state-specific quantum control