Scientific Results

Femtosecond interferometry of propagation of a laminar ionization front in a gas

Year: 2006

Authors: Gizzi LA., Galimberti M., Giulietti A., Giulietti D., Koester P., Labate L., Tomassini P., Martin Ph., Ceccotti T., De Oliveira P., Monot P.

Autors Affiliation: CNR – IPCF, Area Ric, Intense Laser Irradiat Lab, I-56124 Pisa, Italy;
Ist Nazl Fis Nucl, Pisa, Italy;
Physique à Haute Intensité, CEA DSM DRECAM SPAM, Bât. 522 p. 148, 91191 Gif sur Yvette Cedex, France

Abstract: We use optical interferometry to investigate ultrafast ionization induced by an intense, ultrashort laser pulse propagating in a helium gas. Besides standard phase shift information, our interferograms show a localized region of fringe visibility depletion (FVD) that moves along the laser propagation axis at luminal velocity. We find that such a loss of visibility can be quantitatively explained by the ultrafast change of refractive index due to the field ionization of the gas in the laser pulse width. We demonstrate that by combining the post facto phase shift distribution with the probe pulse transit effect in the ionizing region, the analysis of the observed FVD yields significant information on the ultrafast dynamics of propagation of the ionization front in the gas.

Journal/Review: PHYSICAL REVIEW E

Volume: 74 (3) part 2      Pages from: 036403-1  to: 036403-5

KeyWords: electron-beams; laser plasmas; channel; pulses; helium
DOI: 10.1103/PhysRevE.74.036403

Citations: 18
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