The evolution of the filamentation of a femtosecond laser pulse in air is measured. The divergence of the filament core is almost constant over a long distance, encompassing a zone with efficient ionization followed by another where ionization is much weaker. At the end, the core diverges out linearly with a low divergence due to self-spatial filtering.
© 2007 Optical Society of America
Original Manuscript: July 12, 2007
Revised Manuscript: September 19, 2007
Manuscript Accepted: October 23, 2007
Published: December 3, 2007
Yanping Chen, Francis Théberge, Olga Kosareva, Nikolay Panov, Valerii P. Kandidov, and See Leang Chin, "Evolution and termination of a femtosecond laser filament in air," Opt. Lett. 32, 3477-3479 (2007)