Speaker
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Synopsis: Optical probing of magnetization dynamics has traditionally relied on analyzing the polarization of plain Gaussian beams. Recently, we introduced a novel approach – Magnetic Helicoidal Dichroism (MHD) – based on analyzing the reflectivity of beams with twisted wavefronts, i.e., beams carrying orbital angular momentum.
While the spin angular momentum of light is widely used in dichroic studies — such as X-ray magnetic circular dichroism or Magneto-Optical Kerr Effect — the orbital angular momentum (OAM) degree of freedom has been far less explored. Recently, some of us demonstrated that OAM can enhance ptychographic XUV imaging
resolution [3]. Besides, by controlling the sign of the incoming OAM, we also showed that it can reveal the orientation of magnetic textures, such as the curling sense of a magnetic vortex [1, 2],
an effect termed Magnetic Helicoidal Dichroism.
Recently, we leveraged this technique to track the ultrafast dynamics of an oriented inhomogeneous magnetic texture. In particular, we identified a transient inversion of the curling sense of a magnetic vortex during its recovery following
partial demagnetization initiated by a femtosecond laser pulse [4]. A key advantage of Time-Resolved MHD is its ability to operate without a real space imaging of the spin texture, enabling
rapid measurements of a meaningful parameter with just a few intensity patterns. These results hold great promise not only for monitoring the dynamics of complex magnetic textures but
also for uncovering new forms of magnetic optical spin-orbit interactions [5].
M Fanciulli 1,2,3, M Pancaldi 4,5, A-E Stanciu6, M Guer2, E Pedersoli 4, D De Angelis4, P
Rebernik Ribiˇc4, D Bresteau2, M Luttmann2, P Carrara2,7, A Ravindran4,8, B R¨osner9,
C David9, C Spezzani4, M Manfredda4, R Sousa6, L Vila6, I L Prejbeanu6, L D.
Buda-Prejbeanu6, B Dieny6, G De Ninno4,8, F Capotondi4, M Sacchi7,10 and T Ruchon2 *
1 CY Cergy Paris Universit´e, CEA, LIDYL, 91191 Gif-sur-Yvette, France
2 Universit´e Paris-Saclay, CEA, LIDYL, 91191 Gif-sur-Yvette, France
3 New Technologies Research Center, University of West Bohemia, 30100 Plzeˇn, Czech Republic
4 Elettra-Sincrotrone Trieste S.C.p.A., 34149 Basovizza, Trieste, Italy
5 Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, 30172 Venezia, Italy
6 Universit´e Grenoble Alpes, CNRS, CEA, Grenoble INP, IRIG-SPINTEC, 38000 Grenoble, France
7 Sorbonne Universit´e, CNRS, Institut des NanoSciences de Paris, INSP, 75005 Paris, France
8 Laboratory of Quantum Optics, University of Nova Gorica, 5001 Nova Gorica, Slovenia
9 PSI Center for Photon Science, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
10 Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, B. P. 48, 91192 Gif-sur-Yvette, France