A laser pulse (seen as a brief white flash at the focus) generates a hot expanding bubble. After reaching maximum size, the bubble collapses and rebounds, involuting to form a jet (in a manner similar to that shown in the simulation found by clicking here). Buoyancy makes it rise, the main large cavity rising with a greater speed than the smaller bubble fragments. This is qualitatively similar to underwater explosion events such as can be used against shipping. (EPSRC contract GR/S01764/01, “An experimental investigation of laser generated cavitation and its effects on surface coatings” - PR Birkin, TG Leighton, JG Frey)