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Putting light to good use

- By Wits University

New research in structured light will have exciting outcomes for telecoms and other industries.

Professor Andrew Forbes is researching how to pack information into light, transmit it over distance and then unpack the information on the other side. He works with a vibrant team in the new Structured Light Laboratory that he established at Wits.

“We do this in both optical fibres and free space and at the classical and quantum levels,” explains Forbes, who took up his Distinguished Professorship in the Wits School of Physics in March 2015. “The aim of our research is to increase traditional bandwidth by at least two orders of magnitude (100 times) and to improve security between remote sites.”

The outcomes would be of interest to the telecoms industry, banks and the military. Light patterning can also be used to image complex structures such as nanostructures for drug delivery.

The achievement of these goals requires input from some of the best minds in physics when you consider that the diameter of an optical fibre is one-tenth the diameter of a human hair.

Enter Forbes, who worked on South Africa’s largest laser project years ago – uranium enrichment. In 2005, he joined the Council for Scientific and Industrial Research’s (CSIR) National Laser Centre, where he established a new research area in structured light (how to pattern light for a range of applications).

“This got me interested in laser beam propagation and the control of light,” he explains. “It was a small step from here to laser beam shaping.”

He explains that the challenge of using patterns of light to transmit information is that you need to be able to create patterns that can travel – and even accelerate – over long distances. You also need to be able to decode them. “Every time you see the light structure that looks like a particular petal shape pattern, that’s the letter ‘A’; another pattern will be the letter ‘B’, and so on. It’s essentially sophisticated Morse code.”

Forbes and his team design the patterns by using digital holograms and are working on designing the most efficient mode of patterning, and on refining the transmission process. They also need to ensure that the information is secure and encrypted – it’s called quantum cryptography.

In addition to its communication potential, light patterning can also be used to image complex structures such as nanostructures for drug delivery.

“To build more complex nanostructures you need to be able to see them so that you can move them around,” he explains. “Our ability to image these complex structures and to use light as a tool to move them around would significantly contribute to the advancement of nanostructures.”

He concludes: “I would like to patent and licence our work for start-up companies. This is what Africa needs – to start with good people and excellence in science and then to make an economic impact by leveraging on this.” 

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