TORONTO – Sajeev John invented the concept of light trapping when he was a doctoral 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, theoretical physicist and professor at the University of Toronto, is this year’s recipient of Canada’s Gerhard Herzberg Gold Medal for Science and Engineering, Canada’s most prestigious scientific award, which includes an increase funding.
“Funding is something that is very valuable to me,” he told CTVNews.ca in a telephone interview.
The Gerhard Herzberg Medal, named after the Canadian physicist who won the Nobel Prize in Chemistry in 1971, is awarded by the Natural Sciences and Engineering Research Council of Canada. The recipient sees its funding increase over five years, totaling $ 1 million.
The light-trapping technology he first thought about over three decades ago has been used to make optical fibers, with applications such as lasers being used in medicine.
“This has actually been used in medical therapies for laser surgery, to guide 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 at present the manufacturing cost is too high due to the level of perfection required.
“The computer application is something that is a little further into the future,” John said.
Instead of supercomputers, John is focusing on how light trapping could change solar technology, which could be crucial in the ongoing fight against climate change.
“The amount of solar energy that rains on the surface is about a hundred thousand times greater than the total energy consumption of all humans on Earth,” he said. “So it’s about capturing it effectively.”
WHAT DOES ‘TRAP THE LIGHT’ MEAN?
John said the idea started when, as a student, he began to wonder if photons, “the elementary particles of light”, could be trapped “by a certain arrangement of matter” in 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, which was first discovered in the 1860s.
“Since that time […] nobody really imagined a way to trap a light wave and some considered it impossible because light is pure energy and it travels so fast, ”said John.
“The idea was to use this wave character. Waves interfere – if a ridge meets a ridge, there is what is called constructive interference, but the ridge meets the trough and they cancel each other out.
“So I was able to propose, theoretically, an arrangement of matter – and by matter, I mean a material like silicon – that if you shaped it geometrically and arranged these pieces of silicon in periodic matter, it would cause light. to interfere with himself in virtually any direction he would like to try to escape from the point where he was created.
The basic idea of trapping the light became his doctoral dissertation, but the idea of how to trap it was explored further in an article in 1987 he wrote while he was an assistant professor at Princeton, which described the theoretical idea of creating a material that could trap light at a scale comparable to its wavelength, so-called photonic bandgap materials.
“This is where the topic really started to take off,” he said. “And it generated a lot of interest because […] now there was actually a little theoretically prescribed path for people to actually think about what kind of material to make that would do that.
Other scientists and groups hoping to experiment with this theory became interested in finding ways to confirm John’s predictions and find applications for the idea.
And scientists are always finding new applications for it, including John.
HUNTING NEW SOLAR TECHNOLOGY
“One of the things I’m interested in right now is trapping light, not from a laser, but from the sun,” John said. “The source of most of our energy. “
His current project is to design solar cells capable of trapping light more efficiently than existing solar products.
“Now sunlight is coming over a very wide range of wavelengths,” he said. “So we have to capture all these waves and we would like to do it in a very thin material, which is very different from standard solar panels.”
He said that by introducing a light-trapping mechanism, you could make solar cells from silicon – the material that much of existing solar panels are made of – much thinner and even flexible.
“You can put them on a variety of different surfaces – construction surfaces, automobiles and even clothing,” he said. “It’s this ability to trap light in a very fine material and a very abundant, non-toxic material like silicon. […] which is, I think, the breakthrough we’re trying to develop into something more technological right now.
Experiments are already underway to test and refine this concept.
John said he had collaborators in Toronto, Australia and Germany working to make this a reality, including experts in traditional solar technology.
“The designs that I developed theoretically are implemented by this group ‘down below’ to put on the top surface of a solar cell, this photonic crystal or light trapping architecture, and that is placed on a structure. silicon, which already has high quality electronics built by the group in Germany which has world records in solar cells, ”said John.
“So even as we speak right now, this is being implemented and tested. I think we will have answers on the efficiency of the devices over the next year.
If this technology works as it was designed, it could change our perception of solar energy, with potential applications as a coating on automobiles or buildings.
“You could make the capture of solar energy a lot more ubiquitous, not just on a few solar farms or a few rooftops,” John said.
He pointed out that silicon is abundant on Earth and is not toxic, and if this method works, it might not require some of the more toxic chemicals required in traditional solar panels.
Another use of this light trapping technology that is being investigated is to use it to produce hydrogen more efficiently by dividing water into gaseous oxygen and gaseous hydrogen.
It’s called photocatalysis, but is sometimes referred to as “artificial photosynthesis,” John explained, because it uses energy from the sun to charge electrons and cause chemical reactions that can transform water, in the same way. that plants use energy from the sun.
Trapping more light would streamline the process.
“If you could collect 10 times more hydrogen then it’s more profitable – that’s the idea behind,” John said.
While his hands are 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 disease even earlier.
“The type of people I interact with, the beauty of the science itself, they are certainly all a tremendous inspiration,” he said.
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