11 February 2011

The achievement of making an object totally invisible could speed things up

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Researchers have managed to make an object invisible in three dimensions. However, despite the popular reference to Harry Potter’s invisible cloak this is not the researchers’ aim. Instead, these results about controlling light on the finest possible scale could speed things up

One of the brains behind the invisible cloak is Professor Sir John Pendry at Imperial College London. “The cloak design has been around since 2006 when David Smith and I published our paper, but the first implementations were for radar waves. They have a long wavelength so everything is bigger and the engineering gets easier. Now it’s happening for visible light, but these cloaks although they are very precisely engineered are very tiny. They cloak fantastically small objects which are only a few microns across. I was surprised that my collaborator Professor Martin Wegener’s group could engineer so small things with such precision so soon. It’s a skillful team developing nanoengineering,” he said.

When Professor Martin Wegener and colleagues at the Karlsruhe Institute of Technology in Germany managed to make an object invisible in three dimensions for the first time in the end of 2009 they were very excited, because things turned out to work much better than they expected. The tiny objects have been cloaked in wavelengths of light close to those visible to humans. “For example, we expected this device to work only at 3 micron wavelength and not at 1.5 microns within the infrared range. That was a surprise and means the design is much more relaxed when it comes to making these structures,” Wegener said. Now the researchers are trying to cloak objects at visible wavelengths. “This is something we are working on and it means that things have to be miniaturized by a factor of two or so. I’m very optimistic that this will happen in the next half year. We’re still at the very edge of what can be done with today’s technology. Nevertheless, with this useful design tool called transformation optics we can make very special lenses which we might see within 5-6 years,” he said.

Pendry and colleagues did not design a cloak because they were particularly interested in hiding things. They guessed if they succeeded with the cloak people would understand how powerful these metamaterials and their design and technology were. He believes this invention instead could benefit Internet users. “This technology is all about controlling light on the finest possible scale and we thought if we could make a cloak that’s so spectacular we could do anything. I think the first applications are going to be about guiding light around the surface of a chip and directing it to where we want it to go. Most of the traffic of the Internet across the Atlantic goes as light in optical fibers, but then you‘ve got to switch it to different places. The first way people thought of was to turn light back into electricity, put it into a computer, let the computer do the switching and then turn it back to light. This is complicated so it’s expensive and it’s also slow because electrons aren’t as fast as light. People have worked on all optical switching and have technology for doing that now but it’s not on a small chip, it’s on a chip the size of a computer. The Internet is still growing with people watching YouTube and downloading videos and so on and the demand for fast data streams is growing enormously, so maybe the pressure will come and generate some funding to make these developments” he said. If Pendry and colleagues succeed the Internet traffic could become faster as well as cheaper.

A whole world has been seduced by Harry Potter’s invisible cloak and the researchers made a smart move by making this comparison to generate more attention to transformation optics. Potter’s cloak will probably never come true, but if it does the discussion of privacy through the perhaps much faster Internet might shift focus. “What a wonderful way of spying. You don’t need a microphone you can just listen to people…terrible, terrible. Perhaps people will pay me not to build it,” Pendry said.

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