Coherence properties of high harmonics and their applications

We recall the main characteristics of high harmonic generation (HHG) by intense laser pulses in gas, which proceed from the fact that HHG is a laser-driven non linear process. We particularly outline the properties of intrinsic, spatial and temporal coherence which are investigated experimentally. We show that they can be controlled through various phase-matching parameters, on account of the particular form of the atomic dipole phase involved in HHG. Finally, we present two feasibility experiments demonstrating that this XUV source can be effectively used in time-resolved interferometry measurements, in particular in the diagnostic of laser-produced ultra-short dense plasmas.