Science@FELS

Session

Nonlinear X-Ray

23 Sept 2026, 16:30

Auditorium (WHGA/001) (Paul Scherrer Institut)

Conveners

Nonlinear X-Ray

• Gregor Knopp (PSI - Paul Scherrer Institut)

80. Solved and unsolved mysteries in EUV and x-ray transient gratings studies of coherent phonons and magnons

Alexei Maznev (MIT)

23/09/2026, 16:30

Invited

Laser-induced transient grating (TG) spectroscopy, in which two crossed short laser pulses produce a spatially periodic material excitation whose dynamics are monitored via diffraction of a time-delayed probe pulse, is a well-established optical technique used to study a wide range of phenomena. The extension of this technique into the EUV and x-ray spectral ranges accomplished in the past...

38. Four-wave mixing in the X-ray domain: Coherent nonlinear four-photon interaction with core-shell electrons

Ana Sofia Morillo Candas (Max Planck Institute fur Kernphysik)

23/09/2026, 16:55

AMO Physics

Invited

We present the experimental demonstration of coherent four‑wave mixing in the X‑ray regime (XFWM). We first demonstrate the process in neon near the K‑edge (870 eV) using single broadband SASE pulses from the Swiss Free Electron Laser [1]. A square spatial mask splits the incoming beam into three cut‑out beams arranged in a ‘folded BOX’ geometry, enabling background‑free signal detection. The...

19. Orders of magnitude enhancement of magnetic soft X-ray transient grating signal at grazing incidence

Peter Miedaner (MIT)

23/09/2026, 17:20

Nonlinear X-ray science

Oral

Transient grating with EUV and soft X-rays has recently emerged as a powerful way to excite and detect nanoscale dynamics. Short penetration depths at these wavelengths have generally limited these experiments to thin films in a transmission geometry. In reflection, near normal incidence, the signal is entirely dominated by surface displacements. Here, we show that soft X-ray TG in a grazing...

106. Nonlinear X-ray scattering reveals EUV-polariton

Christina Boemer (DESY)

23/09/2026, 17:35

Invited

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.
Here, we present a study of the effect in the x-ray regime and report the observation of a novel hybrid-state of light and matter that emerges from this fundamental nonlinear process. In our...

39. Spin Waves Excited by Hard X-Ray Transient Gratings

Nadia Berndt (MIT Chemistry)

23/09/2026, 18:00

Nonlinear X-ray science

Oral

Ever brighter x-ray laser sources give rise to the possibility of using ultrafast hard x-rays to directly drive nanoscale lattice and magnetic dynamics. Recently, hard x-ray excitation of phonons was demonstrated using the x-ray transient grating (XTG) technique [1], but driving of magnetic dynamics in this regime has remained unexplored. In this work, we use XTG to excite magnetic precession...

66. Portable nanofocusing optics for hard X-ray free-electron lasers

Prof. Ichiro Inoue (The University of Tokyo)

23/09/2026, 18:15

Nonlinear X-ray science

Oral

Tight focusing of XFEL pulses is a straightforward and effective approach to increase their fluence and peak intensity. At most XFEL facilities, nanofocusing optics are treated as permanent beamline components and installed in dedicated vacuum chambers to minimize environmental disturbances such as mechanical vibrations and thermal fluctuations. However, their fixed installation often limits...