Laser-driven high harmonic generation (HHG) is a well-established technique for the production of attosecond pulses in the extreme-ultraviolet (XUV). Due to the high intensities required, these XUV sources rely upon chirped pulse amplification systems with typical pulse repetition rates of a few kHz, limiting their application potential. This project aims at extending this capability in developing brilliant, coherent sources of sub-femtosecond XUV pulses at MHz repetition rates. Such sources will open up new applications of coherent XUV light in time-resolved coincidence studies, biomedical imaging, nanoplasmonics as well as XUV holography and lithography.

Our research on (sub-femtosecond) MHz XUV sources is based on two approaches:

1. The generation of XUV pulses via nanoplasmonic field enhancement

Here we focus on the processes leading to HHG occurring in nanostructures of different size, shape and composition. These structures are tailor-made in order to gain sufficient field strength for the formation of XUV light with few-cycle driving laser pulses. We aim to understand, optimize and use processes leading to nanolocalized plasmonic fields within ordered nanostructures for HHG at MHz repetition rates which ultimately reach into the attosecond regime.

Team: Dr. S. Stebbings, F. Süssmann, Y. Yang, W. Schneider & Prof. M. Kling

Partners: Dr. A. Apolonskiy & Prof U. Kleineberg (LMU), Prof. M. Stockman (GSU Atlanta), Dr. J. Schuck & Dr. A. Weber-Bargioni (Molecular Foundry, Berkeley), Prof. E. Rühl (FU Berlin), Dr. V. Yakovlev, Dr. E. Goulielmakis & Prof. F. Krausz (MPQ)

2. Development of a high-power MHz few-cycle laser source

We aim for the development of a passive, phase-stable enhancement cavity which can support and enhance sub-10fs laser pulses for the intra-cavity production of (sub-fs) XUV pulses via high harmonic generation. The enhancement cavity will be seeded by a few-cyle amplified MHz Ti:sa oscillator. The realization of a high-power, multi-pass MHz Ti:sa amplifier is an important step towards the goal of this project.

Team: Dr. S. Stebbings, W. Schneider, N.N., Y. Yang, Prof. M. Kling & Prof. F. Krausz

Partners: Dr. E. Fill, I. Pupeza, J. Kaster, Dr. A. Apolonskiy, A. Vernaleken, Dr. T. Udem, Dr. P. Hommelhoff (MPQ), Dr. A.M. Azzeer & Dr .Z.A. Alahmed (King Saud University)