A simple path to attosecond science
Our doctoral candidate Marco Dassie has published a new paper in J. Phys. Photonics.
Valence electrons are the key players of chemistry: They govern how atoms bond, molecules form and reactions unfold. However, a large portion of their ultrafast dynamics has long been out of reach for attosecond techniques.
Until last year’s pioneering work by our IMPRS-APS alumna Amelie Heinzerling, attosecond pulses in the visible and deep-UV remained elusive. Now, our doctoral candidate Marco Dassie has taken this a step further: He successfully compressed 28 fs laser pulses by a factor of 50 in time and generated attosecond pulses in the visible and deep-ultraviolet (DUV) spectrum – all using just a single optical fiber. The findings were recently published in the journal J. Phys. Photonics, together with colleagues from the attosecond science group and the University of Lille.
Instead of requiring multiple, complex stages, Marco’s setup relies only on a single fiber. This simplicity makes this achievement so exciting, as it could bring attosecond science to a broader research community. “Attosecond pulses are now easily accessible in any lab that has an amplified commercial femtosecond source,” Marco explains. “Especially in the visible and deep-UV spectrum, this opens exciting opportunities to study the dynamics of valence electrons with minimal technical effort.”
Inside the fiber – a capillary filled with gas – the initial near-infrared (NIR) laser pulses experience an interplay of linear and nonlinear propagation effects. Under the right conditions, the pulse becomes shorter and shorter as it travels along the fiber – ultimately culminating in an ultrashort light burst at the end of the fiber. The key to this self-compression lies in the confinement of the light in a narrow waveguide over a long distance, which affects the propagation properties and balances the natural tendency of the light pulse to spread out due to dispersion.
For the first time, the researchers also resolved the electric field waveform of the compressed pulses at the edge of the extreme ultraviolet (XUV) – down to 120 nm – using a technique called nonlinear photoconductive sampling. Remarkably, the measured waveforms remained reproducible over a period of three weeks up to the experimental noise level – despite possible changes in the laser parameters or environmental conditions during that time. The robustness of the method suggests that it is mature for practical application in attosecond experiments.
Marco also shared that one of the biggest challenges was mirror contamination in his setup. While the interaction of laser pulses with valence electrons is what makes this research work so intriguing, it also causes the bonds of some contaminating molecules near the mirror surface to break. Especially when high intensities are involved, this can create a dark carbon layer on the mirrors. Fortunately, there is a solution to clean the mirrors, and the key insight came during one of our annual meetings. We're glad to see that our events enable meaningful scientific exchange!
Original Publication:
Self-referenced sampling of attosecond visible-vacuum ultraviolet electric fields
M. Dassie, D. Kim, F. Tani, M. Agarwal, M. Mamaikin, N. Karpowicz
Journal of Physics: Photonics 8, 015068 (2026)
DOI 10.1088/2515-7647/ae4957