title: Lasing of ambient air with microjoule pulse energy pumped by a multi-terawatt infrared femtosecond laser.
abstract: We report on the lasing action of atmospheric air pumped by an 800 nm femtosecond laser pulse with peak power up to 4 TW. Lasing emission at 428 nm increases rapidly over a small range of pump laser power, followed by saturation above ∼1.5  TW. The maximum lasing pulse energy is measured at 2.6 μJ corresponding to an emission power in the MW range, while a maximum conversion efficiency of 3.5×10(-5) is measured at moderate pump pulse energy. The optical gain inside the filament plasma is estimated to be in excess of 0.7/cm. Lasing emission shows a doughnut profile, reflecting the spatial distribution of the pump-generated white-light continuum that acts as a seed for the lasing. We attribute the pronounced saturation to the defocusing of the seed in the plasma amplifying region and to the saturation of the seed intensity.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Point
authors.forename: Yi
authors.initials: Y
authors.lastname: Liu
authors.forename: Yohann
authors.initials: Y
authors.lastname: Brelet
authors.forename: Sergey
authors.initials: S
authors.lastname: Mitryukovskiy
authors.forename: Pengji
authors.initials: P
authors.lastname: Ding
authors.forename: Aurélien
authors.initials: A
authors.lastname: Houard
authors.forename: André
authors.initials: A
authors.lastname: Mysyrowicz