Research

In a coherent control experiment, light pulses are used to guide the real-time evolution of a quantum system. This requires the coherence and the control of the pulses’ electric-field carrier waves. FERMI is the first fully coherent FEL, and possesses longitudinal coherence, which is not available at SASE FELs.  While many types of experiment performed with optical lasers have also been performed with SASE FELs, there have been none in the class of coherent control, because of the lack of longitudinal coherence. Only recently, the first demonstration of a coherent control experiment was performed [1]. By controlling the relative phase between two time-overlapped pulses with commensurate wavelengths, it was possible to guide the ionization pathways in neon (see Fig.3). Such a result demonstrates phase control at the attosecond level with FERMI, and opens the way for unique experiments in the EUV and soft X-ray regions, with complete control of the wavelength, polarization, phase and intensity. FERMI produces light with wavelengths down to 4 nm, providing access to core levels, and thus chemical specificity in coherent control experiments.
 

[1] K.C. Prince et al, Nat. Photon. 10, 176 (2016).