Following its announcement in September of the successful development of the world’s first digital laser, the Council for Scientific and Industrial Research’s (CSIR’s) National Laser Centre (NLC) aims to apply this newly acquired knowledge and share it with the wider laser industry.
This is according to NLC chief researcher Andrew Forbes, who reports that the digital laser is currently at the stage of being a proof-of-principle demonstrator.
The NLC is the major photonics-based institute in South Africa and was established in 2000, when laser expertise, tech- nology and systems residing in government institutions and science councils at the time were combined, and the centre was transferred to the CSIR in 2003.
The digital laser was developed by the NLC’s Mathematical Optics Research Group, of which Forbes is the leader. The breakthrough, which has been well publicised, arose from experiments run by PhD candidate Sandile Ngcobo – he and Forbes comprise the digital laser team.
The digital laser enables the production of a variety of light patterns using holograms in a much simpler and easier way than before. This has huge potential benefits for a range of disciplines, including manufacturing, medicine and especially photonics-based communications.
The laser allows for arbitrary laser beams to be created on the fly and uses a liquid crystal display (LCD) as one of its mirrors, forming a digitally addressed holographic mirror.
The LCD inside the mirror can display digital images and as the pictures change on the LCD, the laser beam changes accordingly. The beam is digitally controlled in real time.
Forbes says that the development of the digital laser into a prototype for a parti- cular application will require significant engineering work in partnership with experts in a particular application area.
Although he notes that this could take three to five years, the NLC hopes this comes to fruition sooner.
“We want to present the digital laser to the wider laser community, which I will do at the International Society for Optics and Photonics’ (SPIE’s) Photonic West 2014 conference and exhibition in the US.
“I also have some ideas on expanding the power range, making it work at different laser wavelengths. We are also trying to create a version that is pulsed so that the light comes out in packets of energy,” Forbes says.
The NLC’s immediate application areas are communication, where it hopes to encode information into the patterns of light, and medicine, for more accurate surgery and additive manufacturing, where the digital laser might be used as a programmable device to produce the required patterns of light.
The NLC’s Mathematical Optics Research Group has been working for more than five years on digital holography and laser resonators, the combination of which was crucial to form a digital laser. This initiative was funded by the CSIR for fundamental research and later by the Photonics Initiative of South Africa.
Further developments of the digital laser include the demonstration of a tuneable laser that produces flat-top and Gaussian beams using the laser, as well as a pulsed digital laser, which is yet to be released.
Forbes notes that the NLC hopes to make an impact on society through science, whether it be socially by improving health systems or economically by developing new industries and markets.
The original goal for the digital laser was to accelerate the NLC’s own in-house testing of novel laser resonators.
“We have a long-term goal to secure communication systems of the future. Excellence in science has resulted in a wonderful invention. We want to progress in the development of the digital laser by showing that it is useful, rather than being a fun demonstration in the laboratory. The laser has attracted a lot of attention and we hope that the NLC’s being in the spotlight will increase the focus on the laser and the centre,” states Forbes.
He hopes that national funding will also pave the way for similar breakthrough technologies.
Forbes says that South Africa spends less than 1% of its gross domestic product on science and adds that this is far below the international average.
He states that the NLC receives a small grant that covers only half of the actual costs, while the remainder of the costs is covered by conducting contract research. The yearly total budget for the NLC is about R80-million, including funds that are distributed in South Africa in support of photonics research.
The Laser Sources Group at the NLC is developing high-average power systems, high-pulse energy systems and high-peak power systems that operate with near and mid- infrared wavelengths. Applications of such systems include plastics welding and cutting, bloodless surgery, high-speed ranging and remote sensing of gases. Forbes notes that the results of these systems have been published in various high-impact scientific journals.
The group is also establishing an advanced photonics manufacturing facility, which will be used to work closely with clients to develop tailored laser sources suited to their applications.
Such lasers could potentially have combinations of parameters that are not readily available, or have small form factors or have to operate in challenging environments. The group also offers laser characterisation services and consultations on lasers that are commercially available.
“In my group, we are working on tech- nologies for today and for tomorrow. In the immediate horizon is a new laser technology that dramatically increases laser brightness. Brightness is a parameter that captures the energy and the quality of the laser beam. Ideally, one wants both to be high, which means a higher degree of brightness. We think we can improve the brightness of many lasers by more than 100% with our concept,” Forbes states.
The NLC has embarked on a Technology Innovation Agency project to develop a prototype laser based on this concept. A laboratory demonstration has already shown positive results and Forbes believes that the challenge now is to convince large international companies to implement the new technology.
The NLC has also been developing a new laser diagnostic tool for characterising unknown light sources, based on digital holograms. The tool, like the digital laser, uses LCD screens to probe light rather than to create it.
The probing is done in an all-optical system using holograms written on LCD screens. Forbes states that the tool is versatile and can replace almost all the traditional laser diagnostic tools.
“Two of my students, Angela Dudley and Darryl Naidoo, are working on creating a company to commercialise this new tech- nology,” he reveals.
The centre is also developing new tech-niques for secure quantum communication and is testing methods to encode information into single photons – or particles of light – and encrypting this information using the laws of physics rather than a man-made algorithm.
“The idea is to make the communication perfectly secure, since the known laws of nature would have to be wrong for the code to be broken. What makes our work unique is that we encode many dimensions into each photon using the shapes of light and this is done with digital holograms. We are still very much at the laboratory testing stage, but are positive about the future,” Forbes says.
The NLC has a myriad of lasers, with a range of wavelengths, powers and operation modes, including the unique Laser Additive Manufacturing System. The laser in the heart of the system is a 1000 W fibre laser that can be controlled in five axes to provide a platform for laser manufacturing components by adding material instead of removing it.
The NLC also has two high-average power lasers – a 5 000 W gas carbon dioxide laser and a 4 400 W solid-state neodymium-doped yttrium aluminium garnet laser. These systems form the core of the lasers in the Lasers Materials Processing (LMP) division.
The NLC designs and builds its own lasers through its Mathematical Optics Research Group and Laser Systems Group. The Mathematical Optics Research Group designs and builds custom laser resonators to improve laser performance and usually result in a proof-of-principle concept.
The Laser Systems Group has, over the years, specialised in lasers that operate in the midinfrared wavelength range. This wavelength range has good transmission through the atmosphere and, therefore, is useful for the military.
Laser Materials Processing
The NLC’s LMP unit, which aims to provide the best access to laser-based manufacturing technology for the local manufacturing industry, also emphasises the development of new technologies, such as laser additive manufacturing (LAM) and mobile laser-based refurbishment.
LMP unit research group leader Herman Burger explains that LAM is a manufacturing technique that produces a component without having to remove material using a machining operation.
“The LAM technique produces a com- ponent by adding material in layers to a workpiece using a laser beam to fuse powder onto the previous layer until the required part geometry is obtained. The geometry of each layer is defined by a cross section of a computer-aided design model of the required component.
The mobile laser-based refurbishment is based on laser-cladding technology, in which a high-power industrial laser is used to generate a small puddle of molten metal on the surface of a metal, and new material in the form of a metal powder is injected into this weld pool.
When the laser beam and powder injection system are traversed across the workpiece, the metal surface and new layer deposited solidify, creating a new layer of material. This new layer is metal- lurgically bonded to the base material, ensuring excellent adhesion of the new layer to the metal substrate.
The cladded layer can be engineered by varying the material composition to increase the wear properties or corrosion-resistant properties of the base material. Owing to the highly localised heat input, there is little distortion and no significant change in microstructure and associated material performance degradation away from the cladded layer.
Burger says it has been proven that this technology can be used to effectively repair worn or damaged equipment, such as press tools, trim tools, rotating shafts and journals, as well as any other mechanical component which has become redundant owing to surface wear or damage.
The NLC is currently also involved in the development of a large-volume, high-speed selective laser melting system, which is a joint project with aero- nautical engineering and manu- facturing company Aerosud. The main objective of this project is to enable the manufacturing of large titanium components for the aerospace industry.
“The LMP unit focuses on the development of new laser-based manufacturing processes for industry. The drive is always to define development projects based on real industry needs. That is why the group prefers to establish research and development collaborations with industry partners to ensure that the projects we engage in are relevant and will have easy uptake in industry,” he states.
NLC and Education
The Higher Educational Insti-tutions (HEI) group competence area is one of the units in the NLC that has a variety of laser equipment and diagnostics at various laboratories in participating universities in South Africa.
The HEI unit aims to help universities grow the country’s skills base in the natural and laser sciences.
HEI competence area manager Paul Motalane says the unit also has in-house laboratories that are available to research teams on a shared basis.
He says the NLC is positioned to be a significant contributor to higher educational institutions in South Africa and adds that, by managing the African Laser Centre, which fosters laser-based research in Africa, the NLC significantly contributes to positioning Africa as a serious destination for photonics research and development.
The African Laser Centre was launched in 2003 as a programme within the NLC and is aimed at encouraging laser-based science and optics-related research collaboration between African researchers and facilitating researcher and student exchanges between African institutes.
“The NLC also benefits in terms of potential mutually beneficial collaboration with any of the research teams. Most importantly, through the HEI competence area, the NLC is well placed to deliver on one of its key reasons for existence, which is to establish a sustainable, world-class national laser-based research capacity,” Motalane says.
Some of the developments in the HEI unit include Light Detection and Ranging (LiDAR), which is a remote sensing technique mostly used to measure atmospheric parameters such as composition, wind, temperature and pollutants or trace gases, as well as aerosol and cloud properties.
The NLC has developed a unique mobile LiDAR system, which Motalane says is the only one in Africa that is currently available to university research teams that wish to be involved in environmental monitoring and studies, some of which involve pollution, forestry, agriculture, weather and insects.
The HEI team is upgrading this system with the addition of an X-Y scanner and radar to undertake two-dimensional mapping. This system is useful because the researcher is not confined to a fixed laboratory, as the system is mobile and can be taken to any area where the research is to be undertaken.
“The unit works closely with universities using a very success- ful programme, namely the Rental Pool Programme (RPP) grant scheme. The aim of this programme is to stimulate laser-based research at South African higher education institutions and other research organisations such as museums and science councils,” Motalane states.
However, he states that, owing to funding constraints, the RPP grant scheme only applies to universities. Through the programme, the NLC renders technical and scientific support to approved laser-based research projects that are undertaken externally at universities’ own laboratories or at the NLC using user-facility laboratories.
This year, the NLC has 25 laser- based research projects within its RPP grant scheme. Typical research projects include a research team at Rhodes University, in Grahamstown, led by Professor Tebello Nyokong, who is developing special drugs that are suitable for cancer treatment, using a novel treatment called photodynamic therapy.
A research team at the University of the Free State, led by Professor Hendrick Swart, develops special materials that may be used for display screens and lighting. A group at the Nelson Mandela Metropolitan University, in Port Elizabeth, led by Professor Ernest van Dyk, is involved in renewable-energy research concentrating on photovoltaic materials.
“The HEI unit hopes to build and develop sustainable photonics-skilled human capital for the benefit of the country and Africa. Photonics is a key enabling technology of this century. Currently, our thrust is on the development of master’s and doctoral-level students within the various fields of laser science,” Motalane says.