Experimental Observation of Fluidlike Motion of Optical Vortices

We have observed the fluidlike rotation of a pair of identical optical vortices (OV's) as they propagate through free space. Similar to vortex filaments in a fluid, the initial rotation rate is found to be inversely proportional to the squared distance of separation. Owing to unusually small vortex cores, we obtained rotation rates that were 2 orders of magnitude larger than expected for ``conventional'' large core OV's.