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Crystals Show Promise for Optical Communication

photonic crystal



SCIENCE
Researchers in the field of photonics aim to harness the power of light for use in communication and computing devices in a manner similar to how electrons flow through semiconductors. But in order for photonic crystals to function well as circuits, they need very specific defects that control the suppression and enhancement of light emission and bend the light along a prescribed pathway. Two groups report recent advancements toward this goal, representing small steps along the road to superfast optical and quantum computing.

A team from the Massachusetts Institute of Technology (MIT) led by Minghao Qi describe a new method for introducing precise defects into 3-D photonic crystals, the type of structures that will be necessary for optical quantum information processing. The team used lithography, in which a crystal is built up by depositing one layer on top of another, to manufacture photonic crystals. The scientists deliberately introduced point defects that act as waveguides for light at wavelengths useful for telecommunication applications. The fabrication process has relatively low costs and holds promise for a variety of 3-D nanostructures, the researchers write in the current issue of the journal Nature.

A second report in the current issue of the journal Science describes a 3-D photonic crystal, which emits light at optical communications wavelengths, manufactured using a different approach. Shinpei Ogawa and his colleagues at Kyoto University in Japan made a photonic crystal that resembles a stack of wood with each layer turned 90 degrees with respect to the one below it (see image). The team introduced defects within the "woodpile" and found that the defects gave off light whereas light emission was suppressed in other parts of the structure. The results, the authors conclude, "are an important step towards the complete control of photons in [photonic crystals]."

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