South Africa’s Digital Laser
“One day, Ngcobo walked into my office and placed a graph on my desk. The thing is I didn’t expect it to work and when he brought this one particular graph into my office I immediately realised this laser had worked this time and I knew that people all over the world had been trying to make it work. It really was an amazing graph to see, to realise that you’ve just re-invented a 50-year-old technology.
I ran down the corridor shouting, ‘Do you know what this means?’. This was the response of Professor Andrew Forbes, director of the Mathematical Optics Research Group in the National Laser Centre of the CSIR to the development of the first Digital Laser in the world by University of KwaZulu-Natal PhD student, Sandile Ngcobo.
He later added: “The major challenge was a mental barrier, actually, because if you’re trying to do something at the cutting edge and you don’t know that it actually can be done and you keep trying it and every time you try it it fails … then it kind of keeps reinforcing what you believe, ‘Oh, this hasn’t been done because it’s not possible to do’. Getting over that mental barrier was the most difficult thing, but we kept persevering.”
In principle, lasers are simple devices that comprise mirrors, a source of energy, usually light, and a lasing cavity in which the light can be bounced back and forth so as to create a highly-focused beam of a single frequency. In conventional lasers the shape of the emitted light is either not controlled at all or only a single shape can be selected using expensive optics.
In 2013 Ngcobo created the first laser with a beam that can be controlled and shaped digitally.
The solution was simple: instead of placing a light modulator in front of the laser, build it into the device. In this way, the modulator shapes the beam as it is being amplified, with the result that it is already shaped in the required way when it emerges from the laser cavity.
Using this Digital Laser, the operator can change the beam shape at the touch of a button and without any timeconsuming set-up. This dynamic control of laser modes represents a totally new way of thinking about laser technology and has created a platform on which future laser technology is being built, opening up many future applications, from communications to medicine.
Another outstanding South African invention! • Mike Bruton is a retired scientist and a busy writer; mikefishesbruton@gmail.com