Femtosecond laser pulses propagating in air are investigated. For input powers as high as 25 times the self-focusing threshold, the pulses are shown to break up into two spots, which coalesce into a self-guided beam.
Nonlinear Optics: Materials, Fundamentals, and Applications. Technical Digest. Postconference Edition. TOPS Vol.46 (IEEE Cat. No.00CH37174)