title: Time-resolved investigation of low-density plasma channels produced by a kilohertz femtosecond laser in air.
abstract: By employing pump-probe back longitudinal diffractometry, the electron density and decay dynamics of a weak plasma channel created by a 1-KHz fs laser in air has been investigated. With ultrashort laser pulses of 50 fs and low energy of 0.6 mJ, we observe weak plasma channels with a length approximately 2 cm in air. An analytical reconstruction method of electron density has been analyzed, which is sensitive to the phase shift and channel size. The electron density in the weak plasma channel is extracted to be about 4 x 10(16) cm(-3). The diameters of the plasma channel and the filament are about 50 and 150 microm, respectively, and the measurable electron density can be extended to less than 10(15) cm(-3). Moreover, a different time-frequency technique called linearly chirped longitudinal diffractometry is proposed to time-resolved investigate ultrafast ionization dynamics of laser-irradiated gas, laser interaction with cluster beam, etc.
authors.affiliation: State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P. O. Box 800-211, Shanghai 201800, People's Republic of China. michaeljs_liu@mail.siom.ac.cn
authors.forename: Jiansheng
authors.initials: J
authors.lastname: Liu
authors.forename: Zuoliang
authors.initials: Z
authors.lastname: Duan
authors.forename: Zhinan
authors.initials: Z
authors.lastname: Zeng
authors.forename: Xinhua
authors.initials: X
authors.lastname: Xie
authors.forename: Yunpei
authors.initials: Y
authors.lastname: Deng
authors.forename: Ruxin
authors.initials: R
authors.lastname: Li
authors.forename: Zhizhan
authors.initials: Z
authors.lastname: Xu
authors.forename: See Leang
authors.initials: SL
authors.lastname: Chin