Abstract
Sparks in the form of long, thin filaments having quasi-periodic longitudinal light and dark regions (striations) in time-integrated images have been observed in various gases using a CO2 TEA laser. Typically, a 50-mJ pulse will produce a filament 1 cm long and 130 μm in diameter, with more than 150 striations spaced 50 μm apart in atmospheric air. Each striation is associated with the formation of a plasma region by one pulse in a train of pulses from the mode-locked laser, and the filament results from the formation of successive (nearly identical) regions, each displaced from the previous one toward the laser. The possible use of these sparks as a light source in diagnostics is noted.
© 1979 Optical Society of America
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