  The paper describes the production of thin, focused microjets with velocities
up to 850 m/s by the rapid vaporization of a small mass of liquid in an open
liquid-filled capillary. The vaporization is caused by the absorption of a
low-energy laser pulse. A likely explanation of the observed phenomenon is
based on the impingement of the shock wave caused by the nearly-instantaneous
vaporization on the free surface of the liquid. An experimental study of the
dependence of the jet velocity on several parameters is conducted, and a
semi-empirical relation for its prediction is developed. The coherence of the
jets, their high velocity and good reproducibility and controllability are
unique features of the system described. A possible application is to the
development of needle-free drug injection systems which are of great importance
for global health care.
