Abstract

High order harmonic generation (HHG) is a non-linear process resulting from the interaction of an intense and short laser pulse with matter. This process consists in the up-conversion of the laser fundamental frequency to provide a broad frequency comb covering photon energy from UV to XUV , allowing the production of attosecond pulses in a very robust way.

The process of HHG can be understood as a subsequent of 3 steps where an electronic wavepacket is first free in the continuum by tunnel ionisation, driven away then back to the parent ion by the laser field and then recombine with the core inducing the emission of harmonics photons. These 3 steps can be seen as Feynman paths that can be controlled in order to reveal dynamical processes in atoms and molecules. In the last past year I demonstrated a unique technique where conditions can be found to make these Feynman paths interfere. This technique is now named ‘quantum path interferences’. I will present how I first demonstrate this technique in atoms and how it is possible to use it to reveal ultra-fast molecular dynamics after ionisation. It is crucial to found self-referenced technique that allow us to retrieve information on charge migration after ionisation (nuclear and/or electronic) as this is these ultra fast dynamics that underpins structural changes in molecules within activation or inhibition of molecular properties.