Postfilament supercontinuum on 100 m path in air.

Abstract

Pulses at 744 nm with 90 fs duration, 6 mJ energy, and a weakly divergent wavefront propagate for more than 100 m and generate a filament followed by an unprecedently long high intensity (≥1TW/cm2) light channel. Over a 20 m long sub-section of this channel, the pulse energy is transferred continuously to the infrared wing, forming spectral humps that extend up to 850 nm. From 3D+time carrier-resolved simulations of 100 m pulse propagation, we show that spectral humps indicate the formation of a train of femtosecond pulses appearing at a predictable position in the propagation path.