Researchers at Tel Aviv University have for the first time demonstrated the backflow of optical light propagating forward. The phenomenon, theorized more than 50 years ago by quantum physicists, has never before been demonstrated successfully in any experiment until now.
“This phenomenon reveals an unintuitive behavior of a system comprised of waves, whether it’s a particle in quantum mechanics or a beam of light. Our demonstration could help scientists probe the atmosphere by emitting a laser beam and inducing a signal propagating backward toward the laser source from a given point in front of the laser source. It’s also relevant for cases in which fine control of light fields is required in small volumes, such as optical microscopy, sensing and optical tweezers for moving small particles,” Dr. Bahabad says.
Light is similar to quantum particles in that both can be constructed from interfering waves. Such a construction, in which several waves are added together to produce a new wave, is known as a superposition. If a special superposition of waves, all propagating forward, is constructed, the overall wave can realize what’s called “optical backflow“.
The paper has been published in Optica,