title: Gain dynamics of a free-space nitrogen laser pumped by circularly polarized femtosecond laser pulses.
abstract: We experimentally demonstrate ultrafast dynamic of generation of the 337-nm nitrogen laser by injecting an external seed pulse into a femtosecond laser filament pumped by a circularly polarized laser pulse. In the pump-probe scheme, it is revealed that the population inversion between the C(3)Π(u) and B(3)Π(g) states of N(2) for the free-space 337-nm laser is firstly built up on the timescale of several picoseconds, followed by a relatively slow decay on the timescale of tens of picoseconds, depending on the nitrogen gas pressure. By measuring the intensities of 337-nm signal from nitrogen gas mixed with different concentrations of oxygen gas, it is also found that oxygen molecules have a significant quenching effect on the nitrogen laser signal. Our experimental observations agree with the picture of electron-impact excitation.
authors.forename: Jinping
authors.initials: J
authors.lastname: Yao
authors.forename: Hongqiang
authors.initials: H
authors.lastname: Xie
authors.forename: Bin
authors.initials: B
authors.lastname: Zeng
authors.forename: Wei
authors.initials: W
authors.lastname: Chu
authors.forename: Guihua
authors.initials: G
authors.lastname: Li
authors.forename: Jielei
authors.initials: J
authors.lastname: Ni
authors.forename: Haisu
authors.initials: H
authors.lastname: Zhang
authors.forename: Chenrui
authors.initials: C
authors.lastname: Jing
authors.forename: Chaojin
authors.initials: C
authors.lastname: Zhang
authors.forename: Huailiang
authors.initials: H
authors.lastname: Xu
authors.forename: Ya
authors.initials: Y
authors.lastname: Cheng
authors.forename: Zhizhan
authors.initials: Z
authors.lastname: Xu