Coherent Harmonic Generation at DELTA: A New Facility for Ultrashort Pulses in the VUV and THz Regime

Synchrotron radiation sources producing high-brilliance radiation with tunable wavelength in the VUV to X-ray regime are ideally suited to study the structure of matter on the atomic scale. With a pulse duration of typically 30-100 ps (FWHM), however, they cannot resolve dynamic phenomena such as lattice vibrations, phase transitions, chemical reactions, or fast magnetization changes. Mode-locked lasers, on the other hand, produce intense pulses with a duration below 100 fs, but only at near-visible wavelengths. In the quest for short pulse duration and short wavelength, good progress has been made. High harmonic generation (HHG) or X-rays from a laser-generated plasma have become standard techniques in many laser laboratories. Linac-based free-electron lasers (FELs) have reached the Ångström wavelength regime, a pulse duration of a few femtoseconds, and unprecedented peak brilliance [1 Emma, P. 2010. Nature Photonics, 4: 641[Crossref], [Web of Science ®] , [Google Scholar]]. As for conventional synchrotron light sources, pulses of a few picoseconds can be produced by lowering the momentum compaction factor and thus reducing the bunch length (see e.g. [2 Abo-Bakr, M. 2003. Phys. Rev. Lett., 90: 094801[Crossref], [Web of Science ®] , [Google Scholar]]). Even shorter pulses are obtained by combining electron bunches with femtosecond laser pulses.