Intensity clamping measurement of laser filaments in air at 400 and 800 nm

J.-F. Daigle, A. Jaroń-Becker, S. Hosseini, T.-J. Wang, Y. Kamali, G. Roy, A. Becker, S. L. Chin
2010 Physical Review A. Atomic, Molecular, and Optical Physics  
Molecular N 2 fluorescence excited by laser filaments formed from laser pulses at 400 and 800 nm propagating in air is investigated. A comparison showed that, when excited with 400 nm photons, the fluorescence from the first negative band of N 2 + was enhanced by a factor of 6.4 while that of the second positive band of neutral N 2 remained relatively constant. The enhanced N 2 + signal is attributed to a more efficient inner-shell multiphoton process (to the B 2 + u state) at 400 nm leaving a
more » ... arger population of N 2 + ions in the excited state. On the other hand, the stable fluorescence from neutral N 2 is due to the fact that the plasma density is more or less the same at both wavelengths. Using these results, a theoretical model is developed to determine the clamped intensities of the laser filaments at 400 and 800 nm.
doi:10.1103/physreva.82.023405 fatcat:bnyziqjgejhdhkocgm6eduzqrq