Physicist Sajeev John receives the 2021 Gerhard Herzberg Canada Gold Medal for helping harness the flow of photons

November 17, 2021 by Chris Sasaki - A&S News

Theoretical physicist Sajeev John has received Canada’s highest science and engineering honour, the prestigious Gerhard Herzberg Canada Gold Medal.

John is receiving the award for his ground-breaking research and fundamental advancements in confining and harnessing the flow of photons of light in a manner analogous to harnessing the flow of electrons.

The medal also recognizes John for his leadership in efforts to transform this research into groundbreaking applications in optical micro-chips, optical communications and information processing, laser technologies, solar-energy harvesting and clinical medicine — including life-saving surgical tools and techniques.

"I am profoundly honoured and feel singularly energized to bring to broader fruition the work I began on light-trapping crystals," says John, a University Professor in the Faculty of Arts & Science's Department of Physics.

"The Herzberg Gold Medal offers a unique opportunity for creativity and unfettered pursuit of essential applications such as the world’s most efficient, lightweight silicon solar cells; light-trapping to enhance artificial photosynthesis for solar fuel production; development of the most compact lab-in-a-photonic-crystal sensors for early-stage disease detection and diagnosis; and much more."

Named after the Canadian physicist and Nobel laureate in chemistry, the Gerhard Herzberg Canada Gold Medal is given in recognition of the excellence and impact of a recipient’s research. It is awarded annually by the National Sciences and Engineering Research Council of Canada (NSERC).

"Professor John is truly deserving of the country’s highest scientific honour," says Melanie Woodin, dean of the Faculty of Arts & Science. "Not only has his work been foundational, it has also had an impact in physics, chemistry, engineering and medicine, and is leading to advancements that are benefiting people’s lives."

John's research provides a solution to the problem that photons do not tend to flow along confined pathways like electrons but instead disperse or are absorbed.

According to Kim Strong, chair of the Department of Physics, "Professor John’s research laid out the theoretical foundation for special materials — called Photonic Band Gap (PBG) materials — that allow confinement, or localization, of photons to a microscopic region with the size of the wavelength of light."

"Once you know how to confine photons to a single location," she says, "you can confine their motion along prescribed microscopic circuit paths, analogous to the way the motion of electrons is controlled on the nanometer scale in semiconductors."

Following up on his theoretical work, John and his collaborators built the first large-scale silicon PBG material out of a synthetic opal and have created PBG materials that are even easier and cheaper to manufacture.

The groundbreaking work has sparked the development of novel micro-structured materials known as Photonic Crystals, now referred to as 'semiconductors of light.' Ultimately, the breakthrough will enable computer chips to operate with photons instead of electrons.

Among many impacts beyond the lab, research into PBG materials has already produced life-saving advancements in clinical medicine. In 2004, laser surgery was performed on a patient to remove a tumour which had been treated previously but which kept recurring and remained life-threatening. A final surgery was carried out using a hollow-core photonic band gap fiber and was successful. Thousands of similar procedures have been performed using PBG fibers and several major medical centres are now testing PBG-fiber-based laser surgery tools.

In 1984, John received his PhD in physics from Harvard University where he published the original paper on light localization. He was an assistant professor at Princeton University where he pioneered the concept of photonic band gap materials. He joined the University of Toronto in 1989.

John’s research and scientific leadership earned him the 2001 King Faisal International Prize in Science (with Nobel Laureate C.N. Yang). In 2007, the Institute of Electrical and Electronics Engineers (IEEE) awarded him with the International Quantum Electronics Award for "the invention of and development of light-trapping crystals and the elucidation of their properties and applications."

He is holder of a Canada Research Chair in optical sciences and was named an Officer of the Order of Canada in 2017.