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A very thin ‘invisibility cloak’ that reflects the objects around it is the closes scientists have come in an attempt to remake Harry Potter’s famous invisibility cloak.
Invisibility cloaks work by bending the light around an object. The new cloak is very thin and has a flexible design which helps it blend in with its surroundings when wrapped around an object of any shape, researchers say.
The group of scientists at the Lawrence Berkeley National Laboratory (Berkeley Lab), created a fine film made out of a layer of magnesium fluoride (50 nanometres thick = 5.0 × 10-6 centimetres), on top of which they placed tiny gold antennas (30 nanometres thick = 3.0 × 10-6 centimetres). The golden antennas have six distinct sizes that vary from 90 to 175 nanometres wide and 30 to 220 nanometres long.
In order to test the invisibility cloak, they warped it around an object that measured 36 microns in diameter (1 micron = 0.0001 centimetres) and after shining a light on it they observed that the reflection was nearly perfect. The object was essentially turned into a tiny flat mirror.
The gold antennas adjust the scattering of the light, which makes the object that is warpped in the cloak appear to be invisible. Normally, when light reflects off an object it scatters, especially if the object has an irregular shape.
The new ultra-thin cloak has the power to preserve the frequency and phase of light with the help of the gold antennas. The effect it creates is similar to when the light is hitting a mirror. The edges of the new cloak are also invisible, the scientists reported.
“You could cover a tank with it and make it look like a bicycle”, said Xiang Zhang, the leader of the project and director of Martial Science at the Lawrence Berkeley National Laboratory.
However, the trick only works if the gold antennas are properly tuned, in order to match the background. You would have to stay still for the cloak to make you invisible.
Andrea Alù, an associate professor in the Electrical and Computer Engineering Department at The University of Texas at Austin, is sceptical about Zhang’s claims that the cloak can work with larger objects.
The new finding is nevertheless extraordinary. “The beauty of the paper is that you can control the reflection surface at the sub-wavelengths scale”, Alù added.
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Germaine Hicks
Germaine is an avid sports fan and as such, he decided on his current career path with the idea in mind that he would never, ever miss a Yankee game. Until now, he managed to make good on that promise. As you’ve probably guessed, he’s our go-to sports guy.
