Passion for light earns student NSERC prize
Kenneth Chau has discovered that terahertz light can be transmitted through metals
NSERC winner Kenneth Chau
Asked about his research, Kenneth Chau starts talking about “oscillating electromagnetic waves.” What? “Oh,” says the first-year Ph.D. student in the ultra-fast photonics lab of Dr. Abdulhakem Elezzabi at the University of Alberta, “that’s how we always talk about light here in the lab.”
While Chau’s language airily reflects the rarefied jargon of niche physics, the energy behind his words is simple: curiosity is his passion. It’s guided the 24-year-old engineering student to major insights into the nature of light and its interaction with materials.
His research has now earned him the 2005 Natural Sciences and Engineering Research Council of Canada Andr� Hamer Postgraduate Prize, worth $10,000.
A case in point is Chau’s recent discovery that terahertz (THz) light - invisible light whose frequency lies between that of far infrared and microwave radiation - can be transmitted through metals.
“Metals are usually perfect reflectors,” notes Chau. Imagine trying to shine a flashlight through a metal spoon. Impossible, of course. “Yes,” he thought, “but I’ll try it anyway.”
“It was pure curiosity. Professor Elezzabi encouraged me to explore,” Chau said of his master’s research.
He was exploring how samples of solids changed a single wave of THz radiation shone through them. THz radiation is of major interest as an alternative to X-rays for biomedical imaging. With only a fraction of the energy of X-rays, THz rays can still pass through tissues, but without damaging cells.
First, Chau beamed the THz ray through sapphires. Then, with a “let’s just see what happens” approach, he turned the ray onto a sample of chromium powder. To his astonishment, the wave appeared to pass through the sample. With further research, he determined that the THz wave didn’t actually travel directly through the metal. Instead, the light wave energized surface electrons on the metal which in turn propagated a wave of energy through the metal, resulting in the emission of a THz wave on the metal’s far side.
Not only was this fundamental insight published in Physical Review Letters, a top international physics journal, it could have major commercial applications.
Chau has found that different metals alter the THz signal in different ways as it passes through them. This raises the possibility of using metals to tune a THz signal. For example, a THz signal in a photonics communication network could be split in two, with each of the resulting beams separately tuned by a metal.
As a doctoral student, Chau is continuing his THz exploration with greater focus on applied aspects. True to his intrepid nature, he’s onto another project that changes what we think is possible - in this case, a new way of converting sunlight directly into electricity.
When electrons on the surface of a solid are energized by light, they usually randomly scatter, like billiard balls at the first break. But nanotechnology researchers at the U of A have developed tiny structures they can build into solids that act as electron deflectors, channelling energized electrons in a single direction. The technology works with very low-energy light. Now Chau and Elezzabi are developing computational simulations to see if these devices could be used to harness the sun’s THz radiation to produce electricity more efficiently than existing photovoltaic panels.
“I love the research,” Chau said. “I’m an experimentalist at heart, and at the same time I want to see my research applied somewhere.”
Source: U. Alberta Folio