Liquid Light

Spanish physicists have shown how the photons in a beam of laser light might be able to condense into "light droplets" with certain liquidlike properties.

Laser light, passing through a nonlinear optical medium, can undergo self focusing: the very presence of the intense light, with its strong electric and magnetic fields, can modify the material's index of refraction, causing the material to act like a lens.

At some point the streams of laser light making up the beam would have converged sufficiently to form a condensed state in analogy with the Van der Waals forces which create liquid drops from a gas cloud. These "droplets" would not be at rest but would continue to move at the speed of light.

Humberto Michinel (hmichinel@uvigo.es) and his colleagues at the Universidade de Vigo, the Universidade de Santiago, and the Chalmers Tekniska Hogskola (Goteborg, Sweden) argue that the light condensates can be considered as droplets because his study shows that they have these properties in common with liquids: they have a surface tension (elastic resistance to being deflected) and can sustain vortices like those in superfluids.

The light droplets, not yet demonstrated in the lab, would be useful as robust information bits in future optical computers. (Michinel et al., Physical Review E, June 2002.)