  Fragmentation of liquid metal droplets irradiated by linearly and circularly
polarized femtosecond laser pulses is observed in our experiment. The obtained
shadowgraph snapshots demonstrate that a circularly polarized pulse may produce
several randomly-oriented jets effused from the expanding droplets, while a
linearly polarized laser pulse generates strictly the cruciform jets. The
latter orientation is tied with polarization plane, rotation of which causes
rotation of the cruciform jets by the same angle. To shed light on the
experimental data we performed molecular dynamics simulation of droplet
expansion induced by angle-dependent heating.
  Our simulation shows that the jet directions are determined by an oriented
angle-dependent energy distribution within a frontal hemisphere layer of
droplet after absorption of linearly polarized light. As a result, the produced
flow velocity field guided by surface tension forms two high-speed opposite
jets oriented across the electric field vector as in our experiment.
  A shock-wave pulse generated in the frontal layer has angle-dependent
amplitude inherited from the oriented energy deposition. The release part of
shock pulse produces a cavitation zone nearby the droplet center, and thus an
expanding spherical shell is formed from the droplet. The flow velocities
within a rearside hemisphere of the shell, produced after reflection of the
shock wave from the rear side of droplet, generate two low-speed opposite jets
oriented along the electric field vector. Thus we found that the cruciform jets
are originated independently from the frontal and rear sides of droplet, and a
pair of frontal jets is faster than a pair of rearside jets.
