Moving South Africa into the light fantastic
Whereas the 20th century was defined by electronics, this is the century of photonics. “In 2007, the total revenue of photonics exceeded that of electronics and has done so ever since,” says Professor Andrew Forbes from the school of physics at the University of the Witwatersrand (Wits).
Photonics refers to the study of photons, which are single particles of light.
Over the past 10 years, Forbes has done much to put South African photonics on the map.
In 2004, he joined the Council for Scientific and Industrial Research’s national laser centre (CSIR NLC). He established the research group user facility in 2005 and approached local universities to promote photonics. Soon more than 10 university groups were visiting the laboratories every year, with students staying up to a month.
Mathematical Optics Group
Forbes’ own research was also a primary focus. In 2007, he began the Mathematical Optics Group, now one of the most productive laboratories within South African photonics.
While laser beam shaping — a field where the professor is regarded as an international expert — was the start of the research programme it has evolved to include digital holography, optical communication, optical trapping and tweezing, and high-dimensional quantum entanglement.
Digital holography involves changing the shape of a laser beam with a small LCD TV (about the size of a thumb). In 2006, Forbes was the first person in South Africa to introduce digital holography as a tool for the shaping of light.
Forbes and his group are currently exploring new techniques with optical communication. It involves packing information into light, sending it over custom fibre optics, and unpacking it on the other side. “We have demonstrated that we can do this with patterns of light, potentially increasing the bandwidth of present communication systems by orders of magnitude,” says Forbes.
The optical trapping and tweezing technique can be compared to conventional tweezers except the trapping and control is done purely through light. In 2007, Forbes built the first optical trapping and tweezing system in South Africa, demonstrating the control of micro-particles and biological cells.
New frontiers with quantum optics
In 2009, Forbes applied his beam shaping expertise at the single photon level, and created a new quantum optics laboratory. This is where the first quantum entanglement experiment in Africa was conducted. The facility is one of a few in the world and has produced world firsts, such as high-dimensional quantum key distribution.
Understanding quantum entanglement requires understanding a little of the quantum world. The term “classical world” describes our everyday experience of the world. “However, when you go down to the very small, as in the quantum world, things work very differently. In fact, many of the actions appear counterintuitive,” explains Forbes.
Take light as an example. In the classical world, it operates as a particle or a wave. Within the quantum environment, it can act as both. The basic principles of lasers work within the quantum world.
“In the classical world, if you send two particles of light in two different directions, one wouldn’t affect the other. This is not the case in the quantum world,” says Forbes. Photons are inextricably linked on the quantum level and this is known as quantum entanglement.
After producing the first quantum correlations ever seen in Africa in 2011, Forbes could then demonstrate high-dimensional entanglement in 25 dimensions. This has progressed to several world firsts, including the quantum key distribution experiment.
Quantum entanglement is very useful in encryption, among other things. Because of the quantum link between photons (quantum entanglement), if a message is intercepted the person sending the message will see that this has happened, plus the message is destroyed. This makes for the highest level of security. “The only way to decode the message would be if the laws of physics are wrong,” says Forbes.
High-dimensional quantum key distribution is a new technology for encoding information into entangled quantum states and propagating this securely over long distances. This is currently at demonstration stage, but the future is very promising.
In 2012, Forbes developed a technique for measuring light fields called modal decomposition. This was another a world first.
Modal decomposition makes the measurement of unknown laser beams — an essential requirement with industrial lasers — much faster and more accurate. There have been numerous journal outputs and a patent. It is also in the process of being commercialised through a spin-out company.
The first digital laser
Forbes has also been shaping light inside lasers (intra-cavity beam shaping), mostly for industrial applications, since 2005.
There have also been a number of world firsts within this field, including the development of the world’s first digital laser in 2013. This innovation was chosen as one of the top 20 advances in optics of that year by the Optical Society of America.
From research to outreach
His research — only some of which has been described here — has been published extensively in scientific journals, as well as general and popular science media. Forbes and his students have also won over 50 awards at national and international physics events.
He is a founding member of the Photonics Initiative of South Africa (Pisa), which aims to influence the direction of SA photonics. A new Pisa flagship programme will see Forbes leading a consortium to demonstrate long-distance secure quantum communication for space communication.
Forbes sits on numerous national and international photonics committees and is on the editorial board of the Journal of Optics, UK. He has held honorary professorships at the University of Stellenbosch and the University of Kwazulu-Natal, and is an elected member of the South African Academy of Science.
This man, who is committed to driving photonics in South Africa, also plays his part in outreach and public education. He has given numerous talks and demonstrations at primary and high schools, as well as at science shows. He includes the general public through lectures and the media.
In terms of tertiary education, Forbes has delivered photonics course lectures at various universities to promote the subject matter. In 2009, he started a project to introduce photonics into previously disadvantaged institutions.
Due to this intervention, the University of Fort Hare has its first photonics course at fourth year physics level, has graduated its first MSc students, and now has its first PhD students. The intention is to expand the programme to other institutions.
Within Africa, Forbes has organised and hosted several African photonics training workshops, delivered special courses and lectures, and has co-hosted the annual African Laser Centre Student Workshop for the past several years.
New visions for photonics
Forbes became a distinguished professor of physics at the University of the Witwatersrand in March 2015. He has started a new laboratory for structured light, a field within which he has made significant international contributions (structured light describes moulding or controlling light). At the same time, he will continue to work closely with CSIR NLC.
“The future is looking very bright,” says Forbes. In particular, there is a new National Research Foundation project that asks the open question: can a quantum computer be built with classical light? This involves the merging of tools and technology where classical work blends with quantum work.
Since entities such as photons behave differently in the classical world and the quantum world, there is extensive debate as to whether it’s possible to merge these two worlds. “If we are right, there is a grey area where the classical and quantum worlds can be brought together.”