Sajeev John wins Canada's top science award for his work on trapping light in microchips

Professor Sajeev John is the recipient of this year’s Gerhard Herzberg Canada Gold Medal for Science and Engineering, Canada’s most prestigious award for science, for his work in trapping light in microchips.

TORONTO -

Sajeev John first came up with the concept of trapping light when he was a PhD student at Harvard in 1984 — now, decades later, he’s winning awards for the concept and working on how to apply this idea to revolutionize solar technology.

John, a theoretical physicist and professor at the University of Toronto, is the recipient of this year’s Gerhard Herzberg Canada Gold Medal for Science and Engineering, Canada’s most prestigious award for science, which includes a boost in funding.

“The funding is something that's very valuable to me,” he told CTVNews.ca in a phone interview.

The Gerhard Herzberg Medal, named for the Canadian physicist who won the Nobel Prize for Chemistry in 1971, is awarded by the Natural Sciences and Engineering Research Council of Canada. The recipient has their funding boosted for five years, adding up to $1 million in total.

The light trapping technology he first thought of more than three decades ago has been used to make optical fibres, with applications including lasers used in medicine.

“This has actually been used in medical therapies for laser surgery, for guiding high-intensity lights from a flexible endoscope […] to vaporize tumors and things like that,” he said.

This technology could play a key role in future supercomputers, but right now, the manufacturing cost is too high due to the level of perfection needed.

“The computer application is something that's a little bit further into the future,” John said.

Instead of supercomputers, John has his focus turned towards how light trapping could change solar technology — something that could be crucial in the ongoing fight against climate change.

“The amount of solar energy that's raining down on the surface is about a factor of a hundred thousand greater than the total power consumption of all humans on Earth,” he said. “So it’s a matter of capturing it efficiently.”

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WHAT DOES IT MEAN TO ‘TRAP LIGHT’?

John said the idea started when, as a student, he began to wonder if photons, “the elementary particles of light,” could be trapped “by some arrangement of matter” the way that electrons are contained inside atoms.

One thing that makes light very different from other particles is that light also acts as a wavelength, something that was first discovered in the 1860s.

“Since that time […] no one one had really conceived of a way of trapping a light wave and some considered it impossible since light is pure energy and it moves so fast,” John said.

“The idea was to make use of this wave character. Waves interfere — if a crest meets a crest, there's what's called constructive interference, but the crest meets the trough and they cancel out.

“So I was able to come up, theoretically, with an arrangement of matter — and by matter, I mean a material like silicon — that if you geometrically shaped it and arrange these chunks of silicon in a periodic matter, it would cause the light to interfere with itself in practically any direction it would like to try and escape from the point at which it was created.”

The base idea of trapping light became his PhD thesis, but the idea for how to trap it was fleshed out further in a paper in 1987 that he wrote when he was an assistant professor at Princeton, which described the theoretical idea of creating a material that could trap light on a scale comparable to its wavelength, something called photonic band gap materials.

“That's where the subject really started taking off,” he said. “And it drew a lot of interest because […] now there was actually a little bit of a path theoretically prescribed so that people could actually think about what type of material to make that would do this.”

Other scientists and groups hoping to experiment with this theory became interested at that point in finding ways to confirm John’s predictions and find applications for this idea.

And scientists are still finding new applications for it, John included.

CHASING NEW SOLAR TECHNOLOGY

“One of the things that I'm currently interested in is trapping light, not from a laser, but from the sun,” John said. “The source of most of our energy.”

His current project is designing solar cells capable of trapping light more efficiently than existing solar products.

“Now, sunlight comes over a very broad range of wavelength,” he said. “So we have to capture all those waves and we'd like to do it in a very thin material, which is very different from standard solar panels.”

He said that by introducing a mechanism for trapping light, you could make solar cells out of silicon — the material existing solar panels are largely made of — much thinner and even flexible.

“You could put them on a variety of different surfaces — building surfaces, automobiles, and even clothing,” he said. “It's this ability to trap light in a very thin material and a material that is very abundant and non-toxic such as silicon […] which is, I think, the breakthrough that we're trying to develop into something more of a technology right now.”

Experiments are already being run to test and refine this concept.

John said he had collaborators in Toronto, Australia and Germany who are working on making this a reality, including experts in traditional solar technology.

“The designs that I have developed theoretically are being implemented by this group ‘down under’ to put onto the top surface of a solar cell, this photonic crystal or light-trapping architecture, and this is being placed on a silicon structure, which already has the high-quality electronics built by the group in Germany that has world records in solar cells,” John said.

“So even as we talk right now, this is actually being implemented and being tested. I think we'll have some answers about device efficiency within the next year.”

If this technology works as it’s been designed, it could change how we think about solar energy, with potential applications as a coating on automobiles or buildings.

“You could make solar energy capture much more ubiquitous, not just on a few solar farms or a few rooftops,” John said.

He pointed out the silicon is abundant on Earth and is non-toxic, and if this method works, it may not require some of the more toxic chemicals required in traditional solar panels.

Another use of this light trapping technology that is being looked into is using it to more efficiently produce hydrogen fuel by splitting water into oxygen gas and hydrogen gas.

It’s called photocatalysis, but is sometimes thought of as “artificial photosynthesis,” John explained, as it’s using the energy from the sun to charge electrons and cause chemical reactions that can transform water, similar to how plants use the sun’s energy.

Trapping more light would streamline the process.

“If you could collect 10 times as much hydrogen, then it is more cost-effective — that’s the idea behind it,” John said.

Although he’s got his hands full right now, in the future, John said he would like to see if this technology could be used in medical imaging to potentially help detect diseases even earlier.

“The type of people I interact with, the beauty of the science itself, they’re certainly all tremendous inspiration,” he said.