Sajeev John

Condensed Matter Physics, crystals, magnets, superconductors, semiconductors

Developed the theory and built the first materials that can make optical computing a reality.

Sajeev John came to Canada from India when he was four years old. He grew up in London, Ontario, then went on to study physics at the Massachusetts Institute of Technology (MIT) and at Harvard University. He is currently a professor at the University of Toronto.

Dr. John made the theoretical breakthrough that many think will lead to computer chips that operate with photons instead of electrons. The difficulty of using photons instead of electrons is that, by nature, photons of light scatter. They will travel off in any direction and normally cannot be confined or restrained. That is, they cannot be made to travel along a designated path similar to the way electrons travel through wires. (Optical fibers are no different. Photons travel through the fibres by reflecting off the interior walls; they still scatter and are absorbed by the fibre, and need to be regularly "recharged")

The theoretical framework for special materials called Photonic Band Gap (PBG) materials was laid out by Dr. John in his Harvard PhD thesis, and then refined by him while working at Princeton University. The materials would, at least in theory, allow photons to be confined to a single location. Physicists refer to this containment as "localization." It means that the photon is held in one place without scattering or being absorbed by electrons in adjacent atoms, as it normally would. Once you learn how to confine photons to a single location, you can then learn how to confine their motion to a tube, analogous to the way the motion of electrons is confined to a wire.

Many believed that even though such a material could exist in theory, it could not actually be built. However, after returning to Canada to work at the University of Toronto, Dr. John assembled and led an international team of physicists who built the first PBG material out of a synthetic opal. Since then, he and fellow researchers have refined the theory and their techniques, creating PBG materials that are easier and cheaper to manufacture.

The discovery and creation of PBG materials is important because it could lead to a revolution in computing. Computer chips built with optical transistors will run a thousand times faster, use much less power, and will be smaller than computers built with traditional electrical transistors. The PBG materials being created by Dr. John and his team might also turn out to be the essential hardware required for building quantum computers, which can be super fast, solving some problems in seconds rather than years.

Superfast computers are not Dr. John's only area of research though. He is also working on medical imaging and high-temperature superconductivity.

His work with medical imaging uses light as a diagnostic tool. By analyzing the way light scatters and reflects in living tissue, researchers should be able to create devices that can detect certain cancerous tumours before they create any structural damage. The technique will also allow blood tests to be performed without having to draw blood.

Dr. John and his colleagues are also developing a microscopic theory of the superconducting phase of high temperature cuprate superconductors. If successful, the theory might lead to the ability to build superconducting materials that operate at room temperature. Current superconductors need to be cooled to around 200 degrees below zero in order to operate, which makes them difficult and expensive to use.

Author: Jeff Schering

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Image source: University of Toronto

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