Researchers develop new way to generate superluminal pulses

May 3, 2012

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In four-wave mixing, researchers send "seed" pulses of laser light into a heated cell containing atomic rubidium vapor along with a separate "pump" beam at a different frequency. The vapor amplifies the seed pulse and shifts its peak forward, making it superluminal. At the same time, photons from the inserted beams interact with the vapor to generate a second pulse called the "conjugate." Its peak, too, can travel faster or slower depending on how the laser is tuned and the conditions inside the gain medium. Credit: NIST

(Phys.org) -- Researchers at the National Institute of Standards and Technology (NIST) have developed a novel way of producing light pulses that are "superluminal"—in some sense they travel faster than the speed of light. The technique, called four-wave mixing, reshapes parts of light pulses and advances them ahead of where they would have been had they been left to travel unaltered through a vacuum. The new method could be used to improve the timing of communications signals and to investigate the propagation of quantum correlations.