  We study controlled methods of preparing vortex configurations in atomic
Bose-Einstein condensates and their use in the studies of fundamental vortex
scattering, reconnection processes and superfluid sound emission. We explore
techniques of imprinting closed vortex rings by means of coherently driving
internal atomic transitions with electromagnetic fields which exhibit singular
phase profiles. In particular, we show that a vortex ring can be prepared in a
controlled way by two focused co-propagating Gaussian laser beams. More complex
vortex systems may also be imprinted by directly superposing simpler field
configurations or by programming their phase profiles on optical holograms.
This provides the controlled method of studying vortex reconnections in atomic
superfluids. We analyze specific examples of two merging vortex rings in a
trapped two-component Rb-87 condensate. We calculate the radiated sound energy
in the vortex ring reconnection process and show that the vortex relaxation and
the re-distribution of sound energy can be controlled by the imprinting
process. The energy is first concentrated towards the trap center and later
emitted outwards as sound and transformed to surface excitations. As another
such technique, we study creating pairs of 2D point vortices in Bose-Einstein
condensates using a 'light roadblock' in ultra-slow light propagation. We show
how this can be used to study vortex collisions in compressible superfluids and
how these collisions result in energy dissipation via phonons and, sometimes,
annihilation of vortex pairs.
