Laser-induced shock process in under-liquid regime studied by time-resolved photoelasticity imaging technique

Stress enhancement in laser-induced shock process by plasma-confining effect of liquid overlay was demonstrated visually and its dependence on liquid layer thickness was studied. Time-resolved photoelasticity imaging technique in bright-field mode was used to observe the stress wave in solid phase and the shock wave, plasma, and cavitation bubble in the liquid phase simultaneously. From the photoelastic images, intensity of the laser-induced stress wave (LSW) inside a solid was evaluated semi-quantitatively. We prove that LSW is weaker with thinner liquid layer. To achieve the same effect with bulk liquid, the liquid film needs to be thicker than a threshold value. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4798532]