Effect of focusing conditions on laser-induced shock waves at titanium–water interface

Abstract

The spatial and temporal evolution of laser-induced shock waves at a titanium-water interface was analyzed using a beam deflection setup. The focusing conditions of the source laser were varied, and its effect onto the dynamics of shock waves was elucidated. For a tightly focused condition, the speed of the shock wave was ~6.4 Km/s, whereas for a defocused condition the velocities reduced to <3 km/s at the vicinity of the titanium-water interface. When the laser is focused a few millimeters above the target, i.e., within the water, the emission of dual shock waves was observed toward the rear side of the focal volume. These shock waves originate from the titanium-water interface as well as from the pure water breakdown region, respectively. The shock wave pressure is estimated from the shock wave velocity using the Newton's second law across a shock wave discontinuity. The shock wave pressure for a tightly focused condition was 18 GPa, whereas under a defocused condition the pressure experienced was ≤1 GPa in the proximity of target.

Raman spectra from Symmetric Hydrogen Bonds in Water by High-intensity Laser-induced Breakdown

“…The water pressure declines slowly and uniformly19. The shockwave generates approximately 17 Gpa pressure and 350 K temperature2324252627282930 when the shock wave pulse falls (Point 1* in Fig. 2).…”

Stimulated Raman scattering of lattice translational modes in liquid heavy water

“…When the irradiance value of the laser reaches 10 9 W∕cm 2 , heavy water will break down and ionize, generating laser-induced plasma, which causes shock waves to be generated [10]. The basic mechanism of laser-induced plasma is highly complex and nonlinear [11]. The breakdown starts after the focused laser is absorbed.…”

Stimulated Raman scattering from ice-VIII by shock-induced compression in liquid water

“…The water pressure declines slowly and uniformly. 38 The shock wave generates approximately 10 GPa pressure and 270 K temperature 32,36,39,40 when the shock wave pulse falls. Under these conditions, ice-VIII can be obtained.…”