XUV Ultrafast Laser Laboratory

Short light pulses in the extreme ultraviolet (XUV) range find a wide variety of applications in studies on electronic and structural dynamics of molecules and molecular complexes. The modern femtosecond laser technology provides the possibility to develop XUV light sources of femtosecond pulse duration, which is by orders of magnitude shorter than the typical pulse duration of synchrotron radiation and is comparable to the pulse length of a free-electron laser. This can be achieved via upconverting the laser frequency in the process of high-order harmonic generation (HHG) induced in a gas medium. The great advantage of using the HHG method in a pump-probe experiment is that the pump and the XUV-probe pulses are intrinsically synchronized, since typically the same laser system is used to generate both pules.

In our setup, we employ a Ti: sapphire laser system, delivering pulses of 800 nm wevelength and 25 fs duration, to pump the HHG process in argon gas. The beam of the 21st harmonic of the fundamental frequency (32.55 eV photon energy) is selected by means of a reflection zone plate, yielding the XUV pulse duration of 45 fs after monochromatization.

Setup for ultrafast XUV photoelectron spectroscopy based on a HHG light source.