Dynamics of laser-driven shock waves in water

Shock waves were produced in water by directing unfocused 0.4-J, 20-ns ruby (?=0.693 ?m) or 3-J, 8-ns Nd-glass (?=1.06 ?m) laser light onto the metalized surface of a thin plastic foil. The illuminated areas were 0.35 and 2.3 cm2, respectively, corresponding to laser irradiances of 52.6 and 68.4 MW cm-2. The radial propagation velocity and the profile of the generated waves have been measured via double-exposure interferometric holography and shadowgraphy. Using the obtained values of the shock velocities and the fringe shift in the interferograms, the pressure on the shock wave front, the thickness of the compressed water layer, the laser energy consumed in producing this layer, and the time required for its formation have been calculated.