Physicists at the University of East Anglia, working with colleagues in South Africa, have found that light can develop spinning, twisting behavior as it travels through empty space, without needing special lenses, mirrors, or engineered materials. The team prepared beams of structured light in a particular balanced configuration and observed that distinct regions with left- and right-handed spin appeared and separated as the beam moved forward, even though it began with no spin at all.
The finding challenges long-standing assumptions about how light's properties interact. Previously, producing such chiral behavior typically required specialized surfaces, tightly focused beams, or other optical components. The researchers show that a beam's own internal geometry—its topological structure—can determine where and how these spinning patterns emerge during propagation, a mechanism that was thought to be extremely weak and difficult to detect.
According to the researchers, this hidden geometric structure acts like a mathematical fingerprint that remains stable as the beam changes shape. The work could eventually enable more sensitive medical tests, faster and more secure communications, and advanced quantum technologies that use light to transmit and protect information.