Like filmmakers cutting together a movie, physicists have found a way to temporarily tear a hole in a beam of light. Events that occur during a brief period of time remain unseen, as does the hole itself.Moti Fridman and colleagues at Cornell University report the first experimental demonstration of such “temporal cloaking” online July 11 at arXiv.org.While this trick won’t be hiding bank robbers from security cameras anytime soon, it could find its way into optical and electronic devices.
Previous invisibility cloaks hid objects from view by bending light. Just as water flows around a rock in the middle of a river, light waves curve around a cloak and rejoin perfectly on the other side, leaving no trace of their detour.A time cloak conceals an event by changing light’s speed, not its direction.
With the speed of light capped at 299,792,458 meters per second, this trick works only when light travels slower than it would in a vacuum — such as through fiber-optic cables.The Cornell team, who declined an interview pending the paper’s publication, manipulated light in a fiber-optic cable using a time lens, a silicon device originally developed to speed up data transfer. Some of the light passing through this lens speeds up, and some slows down.
The waves divide, Moses-style, creating a gap of darkness. A second lens farther along the cable then stitches the light back together so that it arrives at its destination intact, with no record of a hole — or anything that happened during this brief window of opportunity.
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