Researcher Sandile Ngcobo.
The team has shown that laser beams can be digitally controlled from within a laser device. Their findings have just been published in a prestigious journal, Nature Communications, in the following issue: Nature Communications 4, no 2289, 2 August 2013.
There is hardly a domain of our modern existence which does not benefit from some form of laser technology. The domains range from devices for laser lighting displays in entertainment to office equipment such as laser printers, DVD players at home, barcode scanners in the shops, surgical technology in hospitals or devices to cut and weld industrial materials in factories.
“This groundbreaking development is further evidence of the great potential we have in scientific innovation – that the world’s first digital laser should come from our country is testimony to the calibre of scientists that South Africa has,” says Minister of Science and Technology, Mr Derek Hanekom.
Laser devices normally consist of mirrors, energy (light) and a casing containing a medium, for example crystal or glass. The medium changes the frequency of the light to create a laser beam with the perfect characteristics for these different applications.
In conventional lasers, the shape of the light that comes out is either not controlled at all, or a single shape is selected by expensive optics. For example, when a medical doctor undertakes surgery, the beam must be appropriate for precision-cutting.
Alternatively, the laser light can be shaped after exiting the laser using a spatial light modulator – a liquid crystal display (LCD) that can be digitally addressed with grey-scale images representing the desired change to the light. The CSIR team has demonstrated for the first time that this can all be done inside the laser.
“Our digital laser uses the LCD as one of its mirrors that is fitted at one end of the laser cavity. Just as with LCD televisions, the LCD inside the laser can be sent pictures to display. When the pictures change on the LCD inside, the properties of the laser beams that exit the device change accordingly,” says Prof Andrew Forbes, leader of the mathematical optics research group.
The researchers have shown that this allows a purely digital control of what comes out of the laser (laser modes) in real-time, hence the name ‘digital laser’.
“We showed that by sending an appropriate picture to the LCD, any desired laser beam could be created inside the laser device. This is a significant advancement from the traditional approach to laser beam control, which requires costly optics and realignment of the laser device for every beam change. Since this is all done with pictures, the digital laser represents a paradigm shift for laser resonators,” says Forbes.
In a ground-breaking experiment at the CSIR’s laboratories in Pretoria, the team programmed the LCD to play a video of a selection of images representing a variety of desired laser modes. The result was that the laser output changed in real-time from one mode shape to another.
“The dynamic control of laser modes could open up many future applications, from communications to medicine. Our device represents a new way of thinking about laser technology and we see it as a new platform on which future technologies may be built,” says Forbes.
CSIR Researcher Sandile Ngcobo, who conducted the breakthrough experimental work as part of his PhD studies, believes the significance of the research is to demonstrate the ability within the CSIR to lead innovation in this field.
"I believe the digital laser will be a 'disruptive' technology. This is technology which may change the status quo and which could create new markets and value networks within the next few years or decade. The research into the digital laser continues. It adds to the CSIR’s strong track record in the development of laser technology in mathematical optics,” says Ngcobo.
The work was done in the mathematical optics group at the CSIR National Laser Centre. The team was led by Prof Andrew Forbes, chief scientist and research group leader, supported by post-doctoral fellow, Dr Igor Litvin, and doctoral students, Sandile Ngcobo and Liesl Burger. The CSIR Researcher, Sandile Ngcobo, performed the breakthrough experimental work as part of his PhD studies.
Department of Science and Technology
Tel: (012) 843 6842
Cell: 082 944 0015
Professor Andrew Forbes
Mathematical Optics Research Group Leader
Tel: 012 841 2368
Skype: skype: andrew.forbes7795
Cell: +27 82 823 1836