Shock Waves in Laser-Induced Plasmas

Abstract

The production of a plasma by a pulsed laser beam in solids, liquids or gas is often associated with the generation of a strong shock wave, which can be studied and interpreted in the framework of the theory of strong explosion. In this review, we will briefly present a theoretical interpretation of the physical mechanisms of laser-generated shock waves. After that, we will discuss how the study of the dynamics of the laser-induced shock wave can be used for obtaining useful information about the laser-target interaction (for example, the energy delivered by the laser on the target material) or on the physical properties of the target itself (hardness). Finally, we will focus the discussion on how the laser-induced shock wave can be exploited in analytical applications of Laser-Induced Plasmas as, for example, in Double-Pulse Laser-Induced Breakdown Spectroscopy experiments.

Temporally and Spatially Resolved Emission Spectroscopy of Hydrogen, Cyanide and Carbon in Laser-Induced Plasma

“…The detector pixels are binned in four tracks along the slit direction, resulting in obtaining 256 spectra for each time delay. Figure 3 shows accumulated raw data from 100 consecutive optical breakdown events, recorded at a time The laser-supported plasma expansion is consistent with previous focal volume investigations [27] and with the Taylor-Sedov blast-wave model [28,29]. Increased electron density and temperature occur in the outer region of the plasma kernel as evidenced by the bright-to-dark boundaries that appear to cause multiple reflections inside the shock wave.…”

“…The irradiance in the CN experiments is about 1 order of magnitude smaller than in the air-breakdown visualizations, therefore, the number of breakdown spots along the optical axis is reduced and the apparent shape of the breakdown region would become closer to spherical symmetry. The laser-supported plasma expansion is consistent with previous focal volume investigations [27] and with the Taylor-Sedov blast-wave model [28,29]. Increased electron density and temperature occur in the outer region of the plasma kernel as evidenced by the bright-to-dark boundaries that appear to cause multiple reflections inside the shock wave.…”

Temporally and Spatially Resolved Emission Spectroscopy of Cyanide, Hydrogen and Carbon in Laser-Induced Plasma

“…The laser-supported plasma expansion is consistent with previous focal volume investigations [25] and with the Taylor-Sedov blast-wave model [26,27]. Increased electron density and temperature occur in the outer region of the plasma kernel as evidenced by the bright-to-dark boundaries that appear to cause multiple reflection inside the shock wave.…”

Measurements of Gaseous Hydrogen–Nitrogen Laser-Plasma

“…Increases in electron density at the plasma edges are indications of the expanding shockwave. In order to estimate the shockwave radius as function of time delay, τ, it is advantageous to use the Taylor-Sedov formula [29] for spherically expanding plasma,…”