Optics researchers from The University of Queensland and Nokia Bell Labs in the US have developed a new technique to demonstrate the time reversal of optical waves, which could transform the fields of advanced biomedical imaging and telecommunications.
Time reversal of waves in physics doesn’t mean traveling back to the future; it describes a special type of wave that can retrace a path backwards through an object, as if watching a movie of the traveling wave, played in reverse.
UQ’s Dr. Mickael Mounaix and Dr. Joel Carpenter, together with Dr. Nick Fontaine’s team at Nokia Bell Labs, are the first to demonstrate this time reversal of optical waves, using a new device they developed that allows full 3D control of light through an optical fiber.
“Imagine launching a short pulse of light from a tiny spot through some scattering material, like fog,” Dr. Mounaix said.
“The light starts at a single location in space and at a single point in time but becomes scattered as it travels through the fog and arrives on the other side at many different locations at many different times.
“We have found a way to precisely measure where all that scattered light arrives and at what times, then create a ‘backwards’ version of that light, and send it back through the fog.
“This new time reversed light wave will retrace the original scattering process like watching a movie in reverse — finally arriving at the source just as it began: a single position at a single point in time.”
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