 |
 |
17 Jun 2002
Scientists have watched, for the first time, what happens when an optical vortex reverses its spin.
An optical vortex consists of a stream of photons spiralling around a dark core. By directing a laser through a series of skewed computer-generated holograms in free space, Gabriel Molina-Terriza and colleagues from the Universitat Politecnica de Catalunya, Spain and US-based Arizona University created such a vortex, (Phys.Rev.Letts., 87, no.2).
The skewed holograms diffracted the laser into several light waves, some of which contained the so-called canonical vortices. By carefully filtering the waves, the researchers extracted the diffracted wave that contained a vortex, and then passed it through a cylindrical lens.
Molina-Terriza and colleagues studied the optical vortex and its swirling energy with a charge-coupled-device camera. They noticed that once the vortex had passed through the lens it began to elongate and eventually form an ellipse. At this stage in the vortex's evolution, the researchers also observed its energy spiralling in the opposite direction.
Claiming that their observations are generic to all systems that contain vortices, the researchers believe the work will have direct relevance to other phenomena. "The [observations] can have direct implications to superfluidity, quantum photon states with angular momentum and interacting Bose-Einstein condensates," said Molina-Terriza.
The studies could also offer an insight into larger-scale events like tornadoes and whirl-pools.
 |  |  |  |  |  |  |
| © 2024 SPIE Europe |
|
