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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 groundbreaking 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,  in the Faculty of Arts & Science's .

“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  recognizes the excellence and impact of a recipient’s research. It is awarded annually by the Natural 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 previously treated tumour that was recurring and remained life-threatening. A final, successful surgery was carried out using a hollow-core photonic band gap fibre. Thousands of similar procedures have been performed using PBG fibres and several major medical centres are now testing PBG-fibre-based laser surgery tools.

"The University of Toronto congratulates Sajeev John on this important recognition,” says Professor Leah Cowen, U of T’s associate vice-president of research. “From his groundbreaking work on confining and harnessing the flow of photons to his leadership in exploring applications for his research in optical micro-chips, optical communications and information processing, laser technologies, solar energy-harvesting and clinical medicine – his impact has been remarkable.” 

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 U of T 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  and was named an  in 2017.