Physicist who found a way to trap light wins Canada’s top science prize

November 17, 2021
Physicist who found a way to trap light wins Canada's top science prize
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Sajeev John, a professor and scientist who developed a way to confine and control particles of light, similar to the way electrons are controlled in electronics, has been awarded Canada’s top science prize.

John was named this year’s recipient of the $1-million Gerhard Herzberg Canada Gold Medal — the highest honour given out by the Natural Sciences and Engineering Research Council of Canada (NSERC) — on Wednesday.

The medal is awarded annually for “sustained excellence” and “overall influence” of research conducted in Canada.

“Thanks to his discoveries, it may be possible to process information optically rather than electronically, enabling a supercomputing technology more stable and scalable than quantum computers,” said a statement from NSERC.

The technique is now being used for non-invasive laser surgeries and the development of a thin solar cell “coating” for buildings, cars and even clothing.

John, a professor and Canada Research Chair in Optical Sciences at the University of Toronto, said the phone call from NSERC president Alejandro Adem, informing him he had won, took him by surprise.

While he’s been given more than a dozen other awards, including an appointment as an officer of the Order of Canada and a Citation Laureate celebrating “Nobel-class” scientists, John said this one is “special, in that it comes from my home country and it’s a real shot in the arm in terms of carrying out future research.”

The Herzberg medal comes with up to $1 million in research funding over five years. It was one of 26 prizes announced by the agency Wednesday. All the prizes are awarded based on nominations by peers and colleagues.

How he figured out how to trap light

John, 64, was born in India, but grew up mostly in Ottawa, where his father, also a physicist, did a postdoctoral fellowship, and in London, Ont.

He went to the U.S. for university and completed his PhD at Harvard University at a time when there was a lot of interest in trapping and manipulating electrons in semiconductors, which rely on their ability to behave as both particles and waves.

“My supervisor suggested, ‘Why don’t you do something different from what everyone else is doing?'” he recalled. “And so I started thinking about other types of waves.”

At first, he tried to figure out if it was possible to trap soundwaves; then he realized that doing the same thing with light would be a big deal, “because light is, you know, everywhere.”

A key difference between electrons and light is that light has a much longer wavelength. That means structures to control them needed to be thousands of times bigger than those used to control electrons in a semiconductor, said John.

“So the trick was designing something like that.”

John was a theoretical physicist, though. So once he had his design, the second challenge was bringing together experts in material science and semiconductor physics to actually make it.

The result was the invention of “photonic band gap materials” or “photonic crystals.”

Using trapped light for healing, climate change

One application of such materials has been in laser surgery, used for procedures such as destroying tumours. Traditionally, surgeons had to cut a patient open in order to shine a laser into the right spot. While regular light can be shone in through a fibre-optic cable, requiring only a tiny incision, lasers can still damage the solid cable. 

With photonic band gap materials, light could be guided through a cable with a hollow core. That has allowed it to be used in surgeries on patients who couldn’t withstand the trauma required for traditional laser surgeries.

John’s current research focus, though, is on something quite different and could potentially help tackle one of the biggest challenges of our time — climate change.

“The area that I’m most excited about right now is in using the concept of trapping light to trap light from the sun,” he said.

His goal is to create thin, lightweight, flexible, high-efficiency solar cells by using photonic crystals to trap the light. John envisions such materials being applied to buildings, vehicles — and maybe even clothing, because it’s so lightweight. “So it could make energy harvesting much more ubiquitous,” he said.

He’s collaborating with other researchers around the world, testing the efficiency of early designs.

“The Herzberg Canada Gold Medal will be very useful in attracting other aspiring young scientists to work on my team and be a part of this effort,” John said. “So quite a lot of it is going to be used to, you know, to bring in good PhD students, postdocs, visiting scientists — people that can work on the project.”

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