Generation of a high amplitude shock wave by laser plasma in a water confinement regime has been investigated for an incident 25–30 ns/40 J/$\text{λ=1.064\hspace{0.17em}μ}\mathrm{m}$ pulsed laser beam. Experimental measurements of temporal and spatial profiles of induced shock waves for this regime of laser shock processing of materials were performed using a velocimetry interferometer system for any reflector system. Above a 10 ${\mathrm{GW/cm}}^{\mathrm{2}}$ laser intensity threshold, a saturation of the peak pressure is shown to occur while the pressure pulse duration is reduced by parasitic plasma occurring in the confining water. The observation of the interaction zone with a fast camera system shows that this breakdown plasma, which mainly occurs at the very surface of the water rather than within the water volume, limits the efficiency of the process. This plasma absorbs the incident laser energy, and the power density reaching the target gradually decreases with increasing power densities while the shock-wave duration is correspondingly reduced. Both pressure measurements and plasma observations allow explaining the current limit of high amplitude shock-waves generation by laser plasma in the water-confinement mode and open new research areas for the understanding of breakdown plasma effects at the surface of the confining water.

The first part of this article presents a review of the main process parameters controlling pressure generation in a confined mode. The effect of laser intensity, target material, laser pulse duration, and laser wavelength are, therefore, discussed. An optimized process can then be defined. The second part of this article deals with the surface modifications induced by laser-shock processing. The generation of residual compressive stresses is then highlighted. Finally, in the third part, the interest of laser-shock processing is discussed for several typical applications. A conclusion will present the future trends of this technique.