Role of background reservoir
Femtosecond laser pulses are known to propagate over long distances as robust
filamentary channels in air (and other media).
This is mainly due to a balance between the optical
Kerr effect causing a self-focusing of the pulse and defocusing from the plasma
self-generated due to multiphoton ionization. The important role and the large spatial
extent of the so-called energy reservoir has been demonstrated in a combined
experimental-theoretical study. The robustness of the filament does crucially
depend on diffraction of energy at the edges of the reservoir. This can be seen
from the result of a numerical simulation for the radial energy distribution
of a laser pulse propagating through a pinhole, which terminates the filamentation
process.
W. Liu et al., Opt. Lett. 30 (2005) 2602
Collaboration: S.L. Chin (Laval University, Quebec, Canada)
