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17 Jun 2002
Scientists propose a spiral architecture for commercially viable, three dimensional, photonic materials
Physicists Sajeev John and Ovidiu Toader at the University of Toronto in Canada say that they have created a blueprint of a three-dimensional photonic bandgap crystal that opens a new door for the development of all-optical devices.
Their chiral crystal architecture should result in a material that has a large photonic bandgap in three dimensions and that is easy and affordable to produce. "That's the crux of the matter," said John. "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."
Their design, reported in the 11 May issue of Science, is based on a tetragonal lattice structure - like a cubic lattice with square-shaped spiralling posts that are stretched in one direction. The material, they suggest, can be produced by a microfabrication technique known as glancing angle deposition (GLAD), which means growing the spiralling posts in a one-step process. The physicists' calculations suggest that the structure will have a photonic bandgap between the fourth and fifth bands of the photon dispersion relation that is very robust to variations in the crystal's geometrical parameters.
Previous microstructure designs have been produced using GLAD, but this is the first time that a blueprint defining the geometrical parameters for GLAD-based photonic bandgap synthesis has been proposed, and also the first time that square spiral posts have been proposed as a way of avoiding a phase-shift between spirals.
Prof. John is co-winner of the prestigious 2001 King Faisal International Prize for Science.
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