Interference Measurement of Superposition of Laser-Induced Shock Waves in Water

Time-resolved phase distributions of laser-induced breakdowns and the subsequent shock waves generated by two pulses in water were observed by a pump-probe interference microscopy. When the two pulses overlapped temporally, the optical interference of the two pulses resulted in a fluctuation in pulse energy inducing breakdown. However, the effect of the optical interference could be avoided by delaying one pulse by a time longer than the pulse duration. When shock waves emitted from two breakdown points overlapped, the pressure in the overlapping region was the sum of the pressures of the individual shock waves, showing the possibility of shock synthesis, such as pressure enhancement and wavefront shaping, by inducing multiple breakdowns. (C) 2009 The Japan Society of Applied Physics