We report an efficient transfer of 800 nm energy into both the ultraviolet and the far infrared (IR) during the filamentation in air of an appropriately shaped laser pulse. The multiorder enhancement of the IR supercontinuum in the 3–5 μm atmospheric transmission windows was achieved thanks to spectral-step cascaded four-wave mixing occurring within the spectrum of the shaped femtosecond laser pulse. These results also point out the limit of the self-phase modulation model to explain the spectral broadening of a filamenting laser pulse.
Original Manuscript: December 6, 2012
Revised Manuscript: February 7, 2013
Manuscript Accepted: February 7, 2013
Published: May 1, 2013
Francis Théberge, Philippe Lassonde, Stéphane Payeur, Marc Châteauneuf, Jacques Dubois, and Jean-Claude Kieffer, "Efficient spectral-step expansion of a filamenting laser pulse," Opt. Lett. 38, 1576-1578 (2013)