In the process of high harmonic generation (HHG), several laser harmonics are generated collinearly with the laser beam, at odd multiples of the fundamental laser energy. We are interested in XUV harmonics, which requires a dedicated high vacuum beamline to be selected and refocused on the experimental end stations.

The HHG beamline of Harmonium@LACUS

As shown in the pictures, the harmonics are produced in a gas target in the HHG chamber, followed by a monochromator (MONO).

In Harmonium, we use a special monochromator to select a well-defined XUV harmonic, designed to minimize the temporal broadening of our pulses. The monochromator was developed in collaboration with the CNR-IFN institute in Padova, Italy. The performance of the light source are shown in the graphs below:

Harmonium can generate HHG either in Ar, with a monochromatize flux higher than 1011 ph/s around 37 eV, or in Ne , reaching photon energies higher with 100 eV, with a flux >108 ph/s.

Recently, in collaboration with the LUMES unit, a new light source has been integrated in our setup. The KM Yperion laser employes a new concept to generate narrow bandwidth (<30 meV) XUV pulses at around 10 eV, at a very high pulse repetition rate (1 MHz), ideally suited for ARPES experiments.

To learn more in detail the capabilities of Harmonium, please check the following publications and PhD theses.

Technical publications about Harmonium:

Harmonium: A pulse preserving source of monochromatic extreme ultraviolet (30–110 eV) radiation for ultrafast photoelectron spectroscopy of liquids

J. Ojeda; C. A. Arrell; J. Grilj; F. Frassetto; L. Mewes et al. 

Structural Dynamics. 2016. Vol. 3, num. 2, p. 023602. DOI : 10.1063/1.4933008.

Harmonium: An Ultrafast Vacuum Ultraviolet Facility

C. A. Arrell; J. Ojeda; L. Longetti; A. Crepaldi; S. Roth et al. 

Chimia. 2017. Vol. 71, num. 5, p. 268-272. DOI : 10.2533/chimia.2017.268.
PhD Thesis

Ultrafast Photoelectron Spectroscopy of Liquid Samples

J. J. P. Ojeda Andara / M. Chergui (Dir.)  

Lausanne, EPFL, 2016.