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

• Published in: Physical review. A, Atomic, molecular, and optical physics Atomic, molecular, and optical physics, 2010-08, Vol.82 (2), Article 023405
• Main Authors: Daigle, J.-F., Jaroń-Becker, A., Hosseini, S., Wang, T.-J., Kamali, Y., Roy, G., Becker, A., Chin, S. L.
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; AIR; ATOMIC AND MOLECULAR PHYSICS; BOSONS; CHARGED PARTICLES; COLLISIONS; COMPARATIVE EVALUATIONS; ELECTROMAGNETIC RADIATION; ELEMENTARY PARTICLES; ELEMENTS; EMISSION; EVALUATION; FILAMENTS; FLUIDS; FLUORESCENCE; GASES; IONS; LASER RADIATION; LASER-PRODUCED PLASMA; LUMINESCENCE; MASSLESS PARTICLES; MOLECULAR IONS; MOLECULE COLLISIONS; MOLECULES; MULTI-PHOTON PROCESSES; NITROGEN; NITROGEN IONS; NONMETALS; PHOTON COLLISIONS; PHOTON EMISSION; PHOTON-MOLECULE COLLISIONS; PHOTONS; PLASMA; PLASMA DENSITY; PULSES; RADIATIONS
• ISSN: 1050-2947; 1094-1622
• DOI: 10.1103/PhysRevA.82.023405

Molecular N{sub 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{sub 2}{sup +} was enhanced by a factor of 6.4 while that of the second positive band of neutral N{sub 2} remained relatively constant. The enhanced N{sub 2}{sup +} signal is attributed to a more efficient inner-shell multiphoton process (to the B{sup 2{Sigma}}{sub u}{sup +} state) at 400 nm leaving a larger population of N{sub 2}{sup +} ions in the excited state. On the other hand, the stable fluorescence from neutral N{sub 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.