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Waving the (spectral) wand of invisibility



This is an important step in taking cloaking technology from the lab and in the real world.

The device works by transferring energy from a particular color – red if it is a red apple that you want to make disappear – to other colors in the spectrum. After the wave has passed through the object, & # 39; & # 39; the device restores the light to the original state & # 39; & # 39 ;.

  A broadband wave illuminates an object, which reflects the green light in the example shown, making the object detectable. A cloak of spectral invisibility transforms the blocked color (green) into other colors of the wave spectrum. The wave spreads unaltered through the object, making the object invisible to the observer.

A broadband wave illuminates an object, reflecting the green light in the shown example, making the object detectable. A cloak of spectral invisibility transforms the blocked color (green) into other colors of the wave spectrum. The wave spreads 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 easiest way to think about it is to go back to the basic lessons we are taught about light at school: light is both reflected and absorbed by the objects it meets. A red apple is red because it reflects – or blocks – red light, while absorbing other colors.

If you remove the red from the spectrum, the apple is black. All colors and all the light have been absorbed; no light has been reflected.

In the experiment of the Montreal Institute, which used a green object, the energy of the green part of the spectrum was transferred to the other colors. But after the light was absorbed and passed from the object, the whole spectrum was restored.

"Our work represents a turning point in the search for the invisibility of masking," said Professor Jose Azana, co-author of an article, Invisibility of broadband at open field through the control of the frequency spectrum of reversible waves published in the journal Optica .

In a statement by the Optical Society of America, Professor Azana, said: "We have made a completely invisible target object under the observation of a realistic broadband illumination by propagating the illumination wave. through the object without detectable distortion, just as if the object and the mantle were not present. "

  The invisibility was a staple in the fantasy and fantasy realm. A cloak of invisibility turned out to be a powerful weapon in the Harry Potter series.

Invisibility was a base in the science-fiction and fantasy realm. A cloak of invisibility turned out to be a powerful weapon in the Harry Potter series. Credit: AP

The device has an immediate practical potential: current telecommunications 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 at certain periods of time – preventing interceptors from gathering information by probing a fiber optic network with light to broadband connection.

If all this sounds pretty good, then I suggest you go read a 2011 experiment by Cornell University researchers: they developed a "temporal mantle" that was able to hide a burst of light as if it were never It happened.

So look at this space … while you can still see it.


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