Researchers from the Universities of Glasgow and Southhampton have demonstrated the three dimensional control that is possible to exist over light.

Using a computer-designed hologram, they created threads of darkness embedded in a laser beam. The hologram bends the direction of optical energy flow, so these dark threads form loops. The loops can then be linked together, or tied into knots.

Professor Miles Padgett, Dr Johannes Courtial, and Jonathan Leach in the Optics group in the University of Glasgow's Department of Physics and Astronomy worked in collaboration with Dr Mark Dennis, a University of Southampton mathematician,. Their findings are set out in a paper 'Knotted threads of darkness' which is published in Nature this week (11 November 2004).

The role of the Glasgow group was designing the hologram that produced the exact combination of beams required to form the loops and knots. A laser was used to illuminate the hologram and the detailed structures recorded by a sensitive camera.

This work is experimental confirmation of earlier theoretical predictions made by Dr Dennis, with Professor Sir Michael Berry at the University of Bristol. Scientifically the work dates back to Lord Kelvin, who tried to formulate a theory for atoms made of loops and knots, embedded not within light, but in the fictitious ether.

The team explains: 'In the present day, the ability to synthesize such knots demonstrates the precise three-dimensional control it is possible to exert over light. These dark loops, links and knots are exciting structures in themselves. They could also be used as traps for quantum mechanical matter such as Bose-Einstein condensates.'

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First published: 10 November 2004