Photon sources and instrumentation Figure 1. : (a) In an intensity grating excitation the polarization is constant in space and the intensity is sinusoidally modulated. The resulting signal is dominated by the thermoelastic response, in this case associated with surface acoustic waves. (b) In a polarization grating excitation the intensity is constant across the volume while the polarization is periodically rotating from circular left to circular right. In the resulting signal the thermoelastic response is strongly suppressed (dashed line) and a previously hidden ultrafast dynamics revealed. This dynamic is due to the direct coupling of the light helicity with the magnetic response of the sample. L. Foglia1, B. Wehinger1,2,10, G. Perosa1,3, R. Mincigrucci1, E. Allaria1, F. Armillotta3, A. Brynes1, M. Copus4, R. Cucini5, D. De Angelis1, G. De Ninno1,6, W. D. Engel7, D. Fainozzi1,11, L. Giannessi1,8, E. Iacocca4, N. N. Khatu1,2,9, S. Laterza1,3, E. Paltanin1,3, J. S. Pelli-Cresi1, G. Penco1, D. Puntel3, P. Rebernik Ribič1, F. Sottocorona1,3, M. Trovò1, C. von Korff Schmising7, K. Yao7, C. Masciovecchio1, S. Bonetti2, F. Bencivenga1 1 Elettra - Sincrotrone Trieste S.C.p.A., Trieste, Italy 2 Department of Molecular Sciences and Nanosystems, Ca’Foscari University of Venice, Italy 3 Department of Physics, University of Trieste, Trieste, Italy 4 Center for Magnetism and Magnetic Nanostructures, University of Colorado Colorado Springs, Colorado Springs, USA. 5 CNR-IOM, TASC Laboratory, Trieste, Italy 6 Laboratory of Quantum Optics, University of Nova Gorica, Slovenia 7 Max-Born-Institute for Nonlinear Optics and Short Pulse Spectroscopy, Berlin, Germany 8 INFN Laboratori Nazionali di Frascati, Frascati, Roma, Italy 9 European XFEL, Schenefeld, Germany 10 Present address: European Synchrotron Radiation Facility, Grenoble, France 11 Present address: Institute of Applied Physics, University of Bern, Bern, Switzerland e-mail: laura.foglia@elettra.eu Acknowledgments K.Y. and C.v.K.S. acknowledge financial support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—Project-ID 328545488—TRR 227, project A02. E.P. acknowledges funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 860553. B.W. and S.B. acknowledge support from the European Research Council, Starting Grant 715452 “MAGNETIC-SPEED-LIMIT”. This work was supported in part by the Italian Ministry of Foreign Affairs and International Cooperation. This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences under Award Number DE-SC0024339 (development of 2D pseudospectral LandauLifshitz numerical method for transient gratings). Original paper L. Foglia et al., Nat Commun 15, 10742 (2024); DOI: https://doi.org/10.1038/s41467-024-54799-6. Fig. 1 x Polarization Intensity b 5 4 3 2 1 0 TG signal (counts/shot) Δt (ps) 25 20 15 10 5 0 Polarization TG Residual x Polarization Intensity a 50 40 30 20 10 0 TG Signal (counts/shot) Δt (ps) 25 20 15 10 5 0 Intensity TG Elettra Highlights 2024–2025 157
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