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Interferometric attosecond lock-in measurement of extreme-ultraviolet circular dichroism


Probing the vectorial properties of light–matter interactions inherently requires control over the polarization state of light. The generation of extreme-ultraviolet attosecond pulses has opened new perspectives in measurements of chiral phenomena. However, limited polarization control in this regime prevents the development of advanced vectorial measurement schemes. Here, we establish an extreme-ultraviolet lock-in detection scheme, allowing the isolation and amplification of extremely weak chiral signals, by achieving dynamical polarization control. We demonstrate a time-domain approach to control and modulate the polarization state, and perform its characterization via an in situ measurement. Our approach is based on the collinear superposition of two independent, phase-locked, orthogonally polarized extreme-ultraviolet sources and the control of their relative delay with sub-cycle accuracy. We achieve lock-in detection of magnetic circular dichroism, transferring weak amplitude variations into a phase modulation. This approach holds the potential to significantly extend the scope of vectorial measurements to the attosecond and nanometre frontiers.

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Fig. 1: Interferometric control over polarization states.
Fig. 2: Interferometric control of two phase-locked XUV sources.
Fig. 3: In situ polarization characterization and spatial homogeneity.
Fig. 4: Phase-resolved XMCD.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.


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The authors thank R. Naaman, A. Capua, T. Ruchon and S. Beaulieu for helpful discussions, S. Valencia Molina for providing the synchrotron data and E. Capua and G. Leitus for performing the superconducting quantum interference device measurement. N.D. is the incumbent of the Robin Chemers Neustein Professorial Chair. N.D. acknowledges the Minerva Foundation, the Israeli Science Foundation, the Crown Center of Photonics and the European Research Council for financial support. M.K. acknowledges financial support by the Minerva Foundation and the Koshland Foundation. This project has received funding from the European Research Council under the European Union Horizon 2020 research and innovation program 682978, EXCITERS.

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N.D. supervised the study. D.A. designed and built the experimental set-up. D.A., O.K. and M.K. carried out the measurements and analysed the data. B.D.B. supported the operation of the laser system. All authors discussed the results and contributed to writing the manuscript.

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Correspondence to Nirit Dudovich.

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This file contains more information on the work, Supplementary Table 1 and Supplementary Figures 1–6.

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Azoury, D., Kneller, O., Krüger, M. et al. Interferometric attosecond lock-in measurement of extreme-ultraviolet circular dichroism. Nature Photon 13, 198–204 (2019).

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