Termal self-action of high-power continuons pulse-periodic CO2 laser radiation in air: II. Laboratory experiments
G.N. Grachev1, A.A. Zemlyanov2, A.G. Ponomarenko1, V.N. Tishchenko1, Yu.E. Geints2, A.M. Kabanov2, A.A. Pavlov3,4, Al.A. Pavlov3,4, V.A. Pogodaev2, P.A. Pinaev1, A.L. Smirnov1, P.A. Statsenko1
1Institute of Laser Physics SB RAS, Ac. Lavrentyev's prosp., 13/3, Novosibirsk, 630090, Russia
2V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, 1, Academician Zuev square, Tomsk, 634021, Russia
3Khristianovich Institute of Theoretical and Applied Mechanics of Siberian Branch of Russian Academy of Sciences, 4/1, Institutskaya str., Novosibirsk, 630090, Russia
4Novosibirsk State University, 2, Pirogova Str., Novosibirsk, 630090, Russia
Keywords: лазерное излучение, тепловое самовоздействие, насыщение коэффициента поглощения, laser radiation, thermal self-action, absorption coefficient saturation
Abstract
The results of laboratory experiments on nonlinear propagation of intense pulse-periodic and continuous wave CO2 laser radiation in a gas medium are presented. Experiments were carried out in a cell containing a mixture of air and carbon dioxide at different partial concentrations (~ 1–10%), in the conditions of strong absorption and thermal blooming of laser radiation. The experimental conditions simulated the atmospheric propagation of intense laser radiation at a kilometer-length path. Sharply focused laser beams were used, and the areas of heat release along the beam channel were registered by the shadow imaging method. We found that the focal waist of the laser beam is characterized by the reduced heat release as compared with that in the pre- and post-focal beam regions. The most probable cause of this circumstance is considered to be the resonance absorption saturation of CO2 molecules, which becomes apparent at high intensities in a laser pulse (a “path cleaning” effect). For continuous wave radiation, this effect appears in a lesser extent.
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