Sonographic probing of laser filaments in air.
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.
Yu
Jin
J
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
Mondelain
Didier
D
Kasparian
Jérôme
J
Salmon
Estelle
E
Geffroy
Sylvain
S
Favre
Catherine
C
Boutou
Véronique
V
Wolf
Jean-Pierre
JP