Published: 14 August 2013, 09:22
Together with colleagues from the Max-Planck-Institute of Quantum Optics, the Fraunhofer Institute for Laser Technology Aachen and the University of Aachen, the ACP principal scientists Jens Limpert and Andreas Tünnermann have recently published an original research article on "Compact high-repetition-rate source of coherent 100 eV radiation" (Nature Photonics 7, 608-612, 2013).
Abstract: Coherently enhancing laser pulses in a passive cavity provides ideal conditions for high-order harmonic generation in a gas, with repetition rates around 100 MHz. Recently, extreme-ultraviolet radiation with photon energies of up to 30 eV was obtained, which is sufficiently bright for direct frequency-comb spectroscopy at 20 eV. Here, we identify a route to scaling these radiation sources to higher photon energies. We demonstrate that the ionization-limited attainable intracavity peak intensity increases with decreasing pulse duration. By enhancing nonlinearly compressed pulses of an Yb-based laser and coupling out the harmonics through a pierced cavity mirror, we generate spatially coherent 108 eV (11.45 nm) radiation at 78 MHz. Exploiting the full potential of the demonstrated techniques will afford high-photon-flux ultrashort-pulsed extreme-ultraviolet sources for a number of applications in science and technology, including photoelectron spectroscopy, coincidence spectroscopy with femtosecond to attosecond resolution and characterization of components and materials for nanolithography.