EDM Studio Inc. - Optical Vortices

We are all familiar with the seemingly-bent shape of a straw sitting in a glass of water. This optical illusion occurs when light rays leaving the water undergo a sudden change of direction at the water-air interface. More generally, light bends (refracts) when the medium through which it is travelling varies. Physicists characterize this variation as a material's so-called "index of refraction".

Ring Instability: As the beam propagates, the initially symmetric ring forms two isolated orbiting spots.

In these simulations of actual experiments, a rotating donut-shaped laser beam travels through a specially-prepared crystal. The crystal has an interesting property - its index of refraction is increased by the presence of the laser beam. Where the beam is brightest (orange), the index is increased most. Local changes to the index of refraction are indicated by the dips in the surface.

As the beam propagates, a natural instability causes the ring to break-up into two filaments (middle image, yellow). The increased brightness of the two spots brings a concomittent change to the index of refraction. The stable spots then move off tangentially (bottom image).

Physicists at the Australian National University are investigating ways of suppressing this beam break-up, research that might one day form the basis of self-configurable optical telecommunication or storage devices.