Phys.org  June 28, 2019
An international team of researchers (Spain, USA – University of Colorado) has discovered a new property of light—self-torque. Their experiments involved firing two lasers at a cloud of argon gas—doing so forced the beams to overlap, and they joined and were emitted as a single beam from the other side of the argon cloud. The result was a type of vortex beam. Then they changed the the orbitatl momentum so that the lasers had different orbital angular momentum and they were slightly out of sync. This resulted in a beam that looked like a corkscrew with a gradually changing twist. And when the beam struck a flat surface, it looked like a crescent moon. The researchers noted that looked at another way, a single photon at the front of the beam was orbiting around its center more slowly than a photon at the back of the beam. They called the new property self-torque…read more. TECHNICAL ARTICLE
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