Analysis of spectra of acoustic signals generated by high-power pulsed laser radiation propagating in the atmosphere. 2. Spectra of acoustic signals from laser sparks

Sound generation in the atmosphere upon exposure to high-power milli- and microsecond laser pulses

“…In this section, the characteristics of acoustic signals from long laser sparks made by HPLR focusing into the atmosphere are discussed. In [33], results of two series of measurements were presented. In the first series of measurements, the spark was made by focusing pulsed electroionization CO 2 laser radiation (λ = 10.6 μm, E L max = 500 J, and τ L = 0.3 μs) into the atmosphere at distances of 50-150 m. The laser energy density in the caustic region varied from 9 to 15 J/cm 2 .…”

“…Spectra of acoustic signals recorded in the first and second series of measurements [11,33,34] are shown in Fig. 10.…”

“…For laser energy densities less than this threshold value, the atmospheric aerosol does not change its phase state, and acoustic radiation is generated due to the thermal expansion of the HPLR propagation channel (the thermooptical mechanism of sound pulse generation). Experimental and theoretical investigations into the mechanisms of acoustic wave generation in the atmosphere upon exposure to laser radiation and the special features of acoustic pulses from solid and liquid aerosol particles have been performed at the Institute of Atmospheric Optics of the Siberian Branch of the Russian Academy of Sciences since 1980 [1- 20,22,23,[27][28][29][30][31][32][33][34]41]. A brief review of experimental and theoretical works on laser-induced shock waves through 1990 was presented in [16].…”