Circuits of the future

There is already a technique to make materials for a new generation of circuits

Published: Thursday 30 September 1999

one of the cherished goals of material scientists has been a circuit that has photons of light moving in it, instead of electrons. Such a circuit would not only be several times faster and efficient than the conventional electronic one, but could also be seamlessly integrated into other opto-electronic components. But this kind of a circuit has remained a dream because of the immense practical difficulties involved in the components. Scientists at the University of Toronto have now come up with a method to develop a material that could be used to fabricate the wires of a photonic circuit.

The main component of a photonic circuit would be what is known as photonic band gap ( pbg ) material, which prohibits light transmission in all directions for specific wavelengths. Such materials have been studied for almost a decade now. In the last couple of years, there have been successful tests of variants of pbg for visible light. But now K Busch and S John at the University of Toronto have reported that they are developing a new material, which they call inverse opal. This has a desirable property: it is tunable, meaning that the wavelengths that are blocked by the material can be controlled ( Physical Review Letters , Vol 83, p967).

Applying an electric field can do this. The material is about 75 per cent air surrounded by silicon. A layer of liquid crystal material (like gold) coats the inner surface of the entire material. A tiny electric field is used to control the transmission property of a liquid crystal. This is precisely what happens in liquid crystal displays of laptop computers, for example.

Though the research is still in the initial stages, the telecommunications industry is very interested in this technology. As more and more networks become fibre optic, the idea of photonic circuit components, which obviate the need of conventional circuits, is very lucrative.

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