Mix ‘n’ probe with waves at FERMI

Transient grating pump-probe setup successfully tested at FERMI.

In the first days of July 2014, a team of scientists carried out a transient grating experiment on the DiProI beamline of FERMI, the FEL source operating at the Elettra research center in Trieste, Italy.

In this successful experiment, the scientists split a FEL pulse in two and recombine it at the sample with a finite crossing angle. “This generates a dynamic XUV grating”, says team leader Filippo Bencivenga, “which we then probe by an optical pulse coming from the seed laser of the FEL in a pump-probe, four-wave-mixing scheme. The coherent, non-linear, interaction of the three pulses originated a detectable coherent beam propagating along the phase matching direction.”

Such kind of non-linear XUV/soft x-ray wave-mixing experiments will be further developed at FERMI in a dedicated beamline (EIS-TIMER), also exploiting the unique capability of FERMI to radiate multi-colour seeded FEL pulses. A multi-colour transient grating approach would enable, for instance, to follow charge flows between constituent elements in molecules with femtosecond resolution, or to study energy transfer processes at the molecular scale.