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This is a major step in taking cloaking technology out of the laboratory and into the real world.
The device works by transferring the energy from a particular colour – red if it’s a red apple you want to vanish – to other colours in the spectrum. After the wave has passed through the object, ‘‘the device restores the light to its original state’’.
A broadband wave illuminates an object, which reflects green light in the shown example, making the object detectable. A spectral invisibility cloak transforms the blocked colour (green) into other colours of the wave’s spectrum. The wave propagates unaltered through the object, making the object invisible to the observer. Credit:Luis Romero Cortés and José Azaña, Institut National de la Recherche Scientifique
The simplest way to think of it is to go back to the basic lessons we get taught about light in school: light is both reflected and absorbed by the objects it encounters. A red apple is red because it reflects – or blocks – red light, while allowing the other colours to be absorbed.
If you take red out of the spectrum, the apple is black. All the colours and all the light have been absorbed; none of the light has been reflected.
In the Montreal institute experiment, which used a green object, the energy of the green part of the spectrum was transferred into the other colours. But after the light was absorbed and passed by the object, the full spectrum was restored.
‘‘Our work represents a breakthrough in the quest for invisibility cloaking,’’ said Professor Jose Azana, co-author of a paper, Full-field broadband invisibility through reversible wave frequency-spectrum control, published in the journal Optica.
In a statement from the Optical Society of America, Professor Azana, said: ‘‘We have made a target object fully invisible to observation under realistic broadband illumination by propagating the illumination wave through the object with no detectable distortion, exactly as if the object and cloak were not present.’’
Invisibility has been a staple in the sci-fi and fantasy fiction realm. A cloak of invisibility proved a powerful weapon in the Harry Potter series.Credit:AP
The device has immediate practical potential: current telecommunication systems use broadband waves as data signals to transfer and process information. Spectral cloaking could be used to selectively determine which operations are applied to a light wave and which are “made invisible” to it over certain periods of time – preventing eavesdroppers from gathering information by probing a fibre optic network with broadband light.
If all that sounds pretty cool, then I advise you go and read up about a 2011 experiment by Cornell University researchers: they developed a “temporal cloak’’ that was able to conceal a burst of light as if it had never occurred.
So watch this space … while you can still see it.