title: Sonographic probing of laser filaments in air.
abstract: The acoustic wave emitted from the plasma channel associated with a filament induced by a femtosecond laser pulse in air was detected with a microphone. This sonographic detection provides a new method to determine the length and the spatial profile of the free-electron density of a filament. The acoustic wave is emitted owing to the expansion of the gas in the filament, which is heated through collisions with high-energy photoelectrons generated by multiphoton ionization. Compared with other methods, the acoustic detection is simpler, more sensitive, and with higher spatial resolution, making it suitable for field measurements over kilometer-range distances or laboratory-scale studies on the fine structure of a filament.
authors.affiliation: Laboratoire de Spectrométrie Ionique et Moléculaire, Unité Mixte de Recherche, Centre National de la Recherche Scientifique 5579, Université Claude Bernard-Lyon 1, 43, Bd. Du 11 Novembre 1918, F-69622 Vulleurbanne Cedex, France. jinyu@lasim.univ-lyon1.fr
authors.forename: Jin
authors.initials: J
authors.lastname: Yu
authors.forename: Didier
authors.initials: D
authors.lastname: Mondelain
authors.forename: Jérôme
authors.initials: J
authors.lastname: Kasparian
authors.forename: Estelle
authors.initials: E
authors.lastname: Salmon
authors.forename: Sylvain
authors.initials: S
authors.lastname: Geffroy
authors.forename: Catherine
authors.initials: C
authors.lastname: Favre
authors.forename: Véronique
authors.initials: V
authors.lastname: Boutou
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Wolf