Description
X-ray free electron laser methods provide unique insight into the structure and dynamics of materials by enabling the observation of ultrafast processes on atomic and molecular length scales. Many XFEL experiments rely on advanced X-ray optics to manipulate, split, shape, and focus the beam in order to realize specific experimental methods. Diffractive optics fabricated using lithographic and nanofabrication methods provide an effective solution for many of these applications. Owing to the extreme intensity of XFEL beams, silicon and diamond are typically the preferred materials because of their favorable thermal, mechanical, and radiation-hardness properties.
In my talk, I will first provide a brief introduction to the fabrication of diffractive X-ray optics using modern nanofabrication and lithographic techniques. I will then present several examples of XFEL experimental methods enabled by such optics, including the first demonstration of transient grating spectroscopy in the hard X-ray regime [1, 2], as well as the development of new XFEL methodologies based on amplitude-splitting delay-line schemes [3, 4]. In the soft X-ray regime, I will discuss ongoing efforts toward the development of a single-shot SASE spectrometer at SwissFEL and present recent results on ultrafast imaging experiments performed at FERMI.
References
1. Rouxel, J.R., et al., Hard X-ray transient grating spectroscopy on bismuth germanate. Nature Photonics, 2021. 15(7): p. 499-503.
2. Li, H., et al., Nanoscale ultrafast lattice modulation with a free-electron laser. Nature Physics, 2026. 22(3): p. 483-488.
3. Li, H., et al., Generation of highly mutually coherent hard-x-ray pulse pairs with an amplitude-splitting delay line. Physical Review Research, 2021. 3(4): p. 043050.
4. Fujita, T., et al., Femtosecond x-ray photon correlation spectroscopy enables direct observations of atomic-scale relaxations of glass forming liquids. The Journal of Chemical Physics, 2025. 162(19).
