May 14, 2001 Two University of Toronto physicists have spiralled a new twist out of the old subject of optics by creating a blueprint for a photonic crystal that paves the way for better, faster and perhaps unprecedented optical devices.
In the May 11 issue of Science, University of Toronto physics professor Sajeev John and graduate student Ovidiu Toader report that they have created a blueprint of a three-dimensional photonic bandgap crystal that opens a new door for the development of devices like all-optical micro-transistors, optical wavelength converters and other components for optical microchips. They say it is a simple design that has potentially far-reaching implications for the networking and telecommunications industry.
"In terms of making a material that's three-dimensional with a large photonic bandgap, there's been a bottleneck in the field over the past 10 years," says John, who is also a Canada Research Chair holder. "Other types of designs or blueprints for large photonic bandgaps have been created but their production is so complex or time consuming that for all intents and purposes they are commercially unusable. Our blueprint can be mass-produced at a very low cost, and that's the crux of the matter."
Research institutions around the world have been pouring vast resources into photonics research. The reason: to break ground in new methods and materials that will help us control and manipulate light in ways similar to how semiconductor chips guide the flow of electrons. Light is currently used in fibre optic cable as a super-efficient transmitter of information; in concentrated form, it is also used as laser beams to perform delicate surgery or scan compact discs or bar codes. John and Toader's new blueprint allows optically based technology to be carried at the microscopic level.
The physicists say their design should come as a surprise to fellow scientists who didn't believe it was possible.
"People thought that to cover a broad wavelength range, photonic bandgap materials had to resemble a diamond lattice," explains Toader. "But diamond structures are very difficult to make because they have very intricate three-dimensional designs. In the past, scientists tried to mimic the diamond structure with something called the 'woodpile' structure - looking something like a stack of Lincoln logs - but they are extremely arduous to make. The structure must be grown one layer at a time, and after several years of work, they've only managed to grow about eight layers."
The photonic bandgap crystal design created by John and Toader is based on something called a tetragonal lattice, like a cubic lattice with spiralling posts that are stretched in one direction. They say it is much easier to make and can be done by a micro-fabrication technique known as glancing angle deposition (GLAD), which means growing the spiralling posts in a one step process.
"Photonic bandgap crystals can do most of the functions required in telecommunications," says John. "It allows you to control the flow of light through passive optical devices, but also create active devices that no one has ever made before like micro-transistors. This could affect not only telecommunications but also the computing industry."
John is one of the world's leading experts in photonics research. He is co-winner of the prestigious 2001 King Faisal International Prize for Science. This research was supported by the Natural Sciences and Engineering Research Council of Canada and the John Simon Guggenheim Foundation.
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