Direct focusing of laser induced underwater shock wave from concave surface

Abstract

Underwater micro shock wave generated from metal surface by irradiation of single pulse laser has been investigated and observed with shadowgraph method. In order to produce underwater micro shock wave, flat and concave glasses coated with 100 nm thick titanium have been used. In this experiment, we used relatively low laser intensity, ranged from 0 to 200 GW/m² and shock wave was generated due to photo-acoustic effect in metal induced by laser irradiation. Shock wave was focused immediately using concave surface and we confirmed the focusing effect by optical observation and pressure measurement. The strength of shock wave from concave surface has attained approximately twice of flat one.