Observation of breakdown induced by CO₂ laser with air-breathing mode

In order to study the influence of flight parameters on laser-induced plasma when the pulse CO2 laser is used for the air-breathing mode, the experiment of laserinduced plasma using the UV-preionized TEA CO2 laser made in our laboratory is discussed. A cylinder with a parabolic inner surface was used in this experiment, whose aperture diameter was 60mm, and the focal lengths were 5mm and 10mm. The spectrum of laser-induced plasma, the distribution of characteristic lines, and the temporal behaviors of plasma in air-breathing mode were introduced in detail. The results show that the evolution of laser-induced plasma with air-breathing mode may last 20μs, and the signal intensity reaches maximum at 6μs. When the laser pulse has a complete effect, the signal begins to decay rapidly. In addition, the signal peak value and the persistence time of laser plasma produced by 10 mm parabolic inner surface are higher and longer than those by the short focal length flight.