On the dot: The NRC's quantum-dot laser technology hits the mark

- Ottawa, Ontario

A reliable and inexpensive multi-wavelength semiconductor laser draws global attention

Lasers have been lighting up the world since 1960. You've probably been entertained by laser shows in science centres, and at the light shows on Parliament Hill in our Nation's capital. Lasers are used to deter art thieves in museums, slice through metal in manufacturing and repair failing eyesight. Behind the scenes, they also power performance and image resolution for your smart TV, scan barcodes in the supermarket and connect you to the internet.

Dr. Zhenguo Lu examining semiconductor chips of quantum-dot coherent comb lasers under microscopes.

Laser waves transmit huge amounts of information by sending pulses of infrared light through a transparent, flexible fibre about the thickness of a human hair. These optical fibres are used widely by telecommunications companies to carry voice, internet and cable television data. In order to pack ever more data in those fibres, multiple lasers emit at different wavelengths (or channels) at one end of the fibre, and are sorted by filters at the other end.

As technological connectivity grows by leaps and bounds, markets are demanding increasingly higher data rates and more channels, requiring superior performance in consumer electronics and optical networks. Existing technology is struggling to keep up.

Historically, fibre-optic networks needed hundreds of individual semiconductor lasers to carry data. Those lasers consume power, contributing to the ever growing power demands on the system. For example, data centres consume as much energy as the entire civil aviation sector. This amounts to about 5% of our total energy consumption, with the demand doubling every 5 years. Lasers are also very heat-sensitive, so their output fluctuates with temperature. At 85 °C they might need 3 times as much current to produce the same amount of light as at 25 °C. To maintain the output, developers must either cool them down or introduce extra circuitry, a costly and time-consuming exercise.

"A promising solution to these issues is the quantum-dot (QD) laser," says Zhenguo Lu, Team Leader of Photonics at the Advanced Electronics and Photonics Research Centre of the National Research Council of Canada (NRC). "QDs are tiny nanocrystals made of semiconducting material. With enough dots—millions or billions—a laser will emit at multiple wavelengths, using less space and power, while output remains steady regardless of the temperature."

Connecting the dots

Dr. Zhenguo Lu experimenting with quantum dot coherent comb lasers for terabit/s networking systems.

After a decade of research into laser technology, Lu and his project team demonstrated an innovative QD multi-wavelength laser garnering the interest of a number of collaborators, including a Canadian start-up who included the technology in their product offering as of 2015. Lu's team has since continued developing the technology for optical coherent network systems and 5G and beyond wireless networks. "We demonstrated record-breaking data transmission capacity of 12.03 terabits (Tbits) per second by using only a single QD laser," he says. A single semiconductor laser can transmit more than 15.6 million high-resolution Netflix movies.

Lu points out that this trailblazer will allow even the highest-performing microchips to operate consistently at temperatures of up to 180 oC. Since it has many wavelengths, one QD laser can be used to carry different data streams, unlike previous networking systems that needed hundreds of individual lasers to carry data. "Old networks were large and cumbersome and consumed a lot of power," he adds. "By contrast, our QD laser-based solution uses nanotechnology, so it is not only some 30 times smaller, but also powerful enough to lower that energy demand."

While this approach will revolutionize the industry, Lu admits that it still needs considerable R&D before it can be marketed. The good news is that a number of academic and industry collaborators are working closely with the NRC to pull all the pieces together.

A key partner in the R&D is Karin Hinzer, University of Ottawa Professor and Research Chair in Photonic Devices for Energy. "Our research group takes photonic devices such as lasers and solar panels and makes them ultra efficient and cost effective," she says. "Quantum-dot nanomaterial is an attractive technology because it is compact and uses very little electricity." The collaboration means that the 2 research groups can share not only knowledge, but also software and hardware for assorted tests. Hinzer reports that they have strong support from the NRC research centre's High-throughput and Secure Networks Challenge program.

Prototyping is the final step in development before the product can be launched. One of the research centre's clients, Ciena Inc., has purchased QD lasers and is testing various prototypes. A global networking systems, services and software company, Ciena sees potential for QD technology applications in multi-carrier optical transmitters.

"The Advanced Electronics and Photonics Research Centre's Canadian Photonics Fabrication Centre (CPFC) is a world-class R&D resource and trusted R&D collaborator," says Maurice O'Sullivan, Ciena's Senior Director, Optical Systems. "Working together provided us with a better understanding of the technology."

Dotting the i's and crossing the t's

The Quantum-Dot Laser Team won the NRC's Research and Technology Breakthrough award in 2018. Featured from left to right:
Back row – Martin Vachon, John Weber, Craig Storey
Front row – The NRC's President: Iain Stewart, Youxin Mao, Zhenguo Lu, Chun-Ying Song, Philip Poole
Absent from this photo: Jiaren Liu

These high-speed, low-power, temperature-stable QD lasers have caught the attention of global technology giants that see the value of integrating them within their systems to reduce costs while meeting rapidly growing global needs.

Lu has fielded considerable interest in the solution, which uses materials that can be produced in only 2 countries—France and Canada. His published papers are cited often, he is in high demand internationally as a conference speaker and has had discussions with many multinational companies.

The QD laser market is projected to expand to around US$50 billion by 2025 with a compound annual growth rate of some 60%. With their innovative QD technology, the NRC and its partners have a winning formula for "exciting" this world.

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