Droplet deformation and fragmentation by ultra - short laser pulses

We report on the experimental studies of the deformation and fragmentation of liquid metal droplets by picosecond and subpicosecond laser pulses. The experiments were performed with laser irradiance varying in 10-10 W/cm range. The observed evolution of the droplet shape upon the impact dramatically differs from the previously reported for nanosecond laser pulses. Instead of flattening the droplet undergoes rapid asymmetric expansion and transforms into a complex shape which can be interpreted as two conjunct spheroid shells and finally fragments. We explain the described hydrodynamic response to the ultra-short impact as a result of the propagation of the laser-induced convergent shockwave through the volume of droplet.