Angela Pirri - Novel Coherent Sources

Novel Coherent Sources and Applications

The fascinating world of non-linear process

What happens if short and intense laser pulses interact with gaseous targets?

At LENS, European Laboratory for Non-linear Spectroscopy, we investigated the High Order Harmonic Generation process, HOHG, the properties of harmonic radiations, and we used these Extreme ultraviolet and ultrashort radiations with Ramsey Spectroscopy. HOHG is a powerful tool as we can use in experiments a novel coherent source in the extreme ultraviolet (xuv) and soft X-ray regions, where others sources are scarce and not so user-friendly. Moreover, they are the starting point for the generation of blocks or trains of attosecond pulses.

Interference fringes were observed for the 15th harmonic in argon. The bright central region corresponds to emission from the short electronic trajectory, while the outer diffuse halo derives from the long one.

Phys. Rev. A

Picture of the harmonic generation region in the 5-hole gas jet configuration; the plasma light generated by intense laser ionization is evident in correspondence with the gas jets, separated by about 400 micrometers.

Phys. Rev. A

Fringe contrast vs pulse delay, where the solid lines are theoretical curves obtained for varied values of the Fano parameter.

Optics Letters

The first use of the original two-pulse Ramsey scheme to study high-lying bound atomic states, whose long-level lifetimes allow us to put to a stringent test the spectral resolution limits of the technique.