Fragmentation process induced by nanosecond laser pulses

A fiber-optic stress sensing technique is applied to evaluate the fragmentation mechanism induced by nanosecond laser pulses. We demonstrate that fragmentation is achieved in response to the shock induced by the laser initiated plasma expansion. This shock is followed by a second shock of similar magnitude observed some hundreds of microseconds later, which originates from the collapse of the induced cavitation bubble. The strength of this second shock is able to induce further fragmentation of the target. This is in contrast to the fragmentation process observed with microsecond pulses where the shock induced by the cavitation bubble collapse is the governing phenomenon.