Abstract
The threshold of a laser-induced breakdown of air is determined experimentally
and theoretically. We find that the ionization of air has two steps: the first step is a
multi-photon ionization process, which provides enough “seed electrons” to initiate the
next step, and the second one is predominated by cascade ionization, which continues to
produce free electrons geometrically until the critical free-electron density for
breakdown is reached. So a two-step model based on the Morgan ionization model is
established to describe the breakdown process. It is found that the time node dividing
the two steps is about 9.8 ns in atmospheric air, and the threshold derived from the
two-step model proposed here is more consistent with the experimental results than
traditional ionization model.
© 2016 Chinese Laser Press
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