Within the tight confines of a fiber-optic cable, some researchers at Cornell have managed to create an invisible flash of light. It's invisible not because the flash is manipulated to be hidden, but because the stretch of time during which it happened is erased by the time the flash gets to the other end of the cable. It has achieved temporal invisibility.
Traditional invisibility cloaks confuse the senses by taking the incoming light from behind an object and reproducing it, perfectly, on the other side. Sometimes the light is recorded and then reproduced. Sometimes the light is bent from the far side to the onlooker's side, around the object. Many of these devices, while not good enough to fool the eye in every situation, are fairly advanced. Cornell researchers have taken a different tack. They've created a set up that erases any visual record of the time when the object blocked out the background.
Their temporal invisibility set-up is rudimentary right now. It's simply the lack of a flash in a fiber-optic cable, but it may represent a new approach to invisibility. Light waves speed down a fiber-optic cable until they hit a time lens. The word 'time lens' sounds awesome, but it has been around for a while. It quickens the transfer of data by staggering the light, speeding some waves up and slowing others down. Between these two, is a little hole of darkness. The hole lasts only 15 trillionths of a second, just enough time for small pulses of light to go down the cable. At the other end of the cable, a lens puts back together the original beam of light, as if the pulses had never been.
This is an early step, and not as impressive as other invisibility cloaks, but it's also a new kind of invisibility. Instead of something interactive, that needs to be bent around an object, the world could be made to be just like a video recording. Snip out the bits that shouldn't be seen and put the tape back together, and it's like nothing was ever there in the first place.
Via Science News.
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