Amplified Femtosecond Laser System with High Pulse Repetition Rate

• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: Funded in 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 558156621

We propose the acquisition of a femtosecond laser system with high average power (160 W) and moderately high pulse energy (2×2 mJ) for research in strong-field and attosecond laser physics as well as in nanoscale extreme ultraviolett (XUV) imaging, including time-resolved XUV imaging in particular. Among the requirements, the laser system must be capable of generating spectrally continuous XUV radiation and be equipped with a tunable pump beam. Each beam will be driven by optically synchronized 2-mJ femtosecond pulses. Decisive is industrial-grade reliability. The key research themes defining the requirements specifications are: 1) Ultrafast XUV coherence tomography (XCT), a non-invasive cross-sectional imaging technique with nanoscale resolution invented by the applicant. The new laser system shall make it possible to perform XCT in pump-probe arrangements with 40, subsequently single-digit femtosecond resolution, and in the long run with attosecond resolution. This requires the generation of continuous XUV spectra. The most robust scheme is mixing incommensurate driving frequencies. For single-digit femtosecond resolution, few-cycle pulses are required. An optical parametric amplifier serves for generating tunable pump (probe) pulses. 2) Recording movies of molecular reactions triggered or probed by few-cycle or XUV pulses. Also in this case, tunable pump pulses are required. Particularly useful are tunable UV pulses. The fragments of the reactions are analyzed by kinematically complete momentum spectroscopy. The requirements on the laser system are quite similar to those for XCT. 3) Investigation of ions in strong laser fields. The targets for these experiments range from fundamentally important systems like He+, H+2 , H+3 , and HeH+ to ions never investigated to date. Examples from current projects are Si+, Si2+, Au+, Au2+, and Au+2, which will allow to address long-standing issues in strong-field laser physics with some entirely new perspectives. Experiments on ions naturally require very high intensity and thus high pulse energy and short pulse durations. All projects intended for the laser require a high pulse repetition rate. Absolutely decisive is high reliability. Therefore, we propose an innovative configuration with a pair of optically synchronized ultrafast industrial-grade lasers as the front-end. Its pulses are compressed in a multi-pass cell (MPC), stretched hollow-core fiber (HCF), or cascaded focus compressor. We expect that this approach to strong-field and attosecond laser physics will become a standard within the next few years. It allows creating high XUV fluxes and is ideal for coincidence experiments.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Verstärktes Femtosekunden-Lasersystem mit hoher Pulsrepetitionsrate
• Instrumentation Group: 5700 Festkörper-Laser
• Applicant Institution: Friedrich-Schiller-Universität Jena
• Leader: Professor Dr. Gerhard G. Paulus