Scientists have discovered a surprising ability of light that allows it to develop spinning patterns as it moves through empty space, without relying on special lenses, mirrors, or materials. The finding reveals that light possesses a hidden geometric structure that can influence its behavior in ways researchers previously thought were difficult to achieve.
The discovery comes from an international team led by researchers at the University of East Anglia (UEA) in the United Kingdom, working with scientists in South Africa. Their experiments demonstrate that carefully prepared light can be controlled through its own internal geometry, offering a new approach to manipulating how light spins and twists.
The findings challenge long-standing assumptions about how different properties of light interact. They could eventually lead to more sensitive medical tests, faster and more secure communications, and advanced quantum technologies that use light to transmit and protect information.
Why the Direction of Light’s Spin Matters
One of the most intriguing aspects of the discovery involves chirality, a scientific term describing the difference between left-handed and right-handed structures.
Human hands provide a familiar example. Although they are mirror images of each other, a left hand cannot be perfectly superimposed on a right hand. Many molecules have a similar property, including compounds used in medicines. Two versions of the same molecule can have nearly identical chemical structures yet produce very different effects in the body.
Scientists can distinguish these molecular forms by studying how they interact with light that has a particular rotational behavior. Traditionally, producing and controlling such light has often involved specialized materials, carefully designed surfaces, or powerful lenses that focus beams extremely tightly.
The research demonstrates that appropriately prepared light can develop this behavior naturally as it travels, without requiring those additional optical components.
“Our work shows that light can naturally develop this handed behavior all on its own,” said Dr. Kayn Forbes from UEA’s School of Chemistry, Pharmacy and Pharmacology.
“You just have to prepare it in the right way.
“Most people think of light as traveling in straight lines. But scientists can also create structured light — light whose brightness, shape, and direction are carefully arranged.
“One extreme example is light that twists as it travels, forming a corkscrew shape known as an optical vortex. Each twist can carry information, making this kind of light valuable for high-speed internet, secure communications, and advanced sensors.
“Light can also spin as it travels, depending on how it is polarized. This spin can be left-handed or right-handed — another form of chirality.”
Scientists Discover How Light Develops a Hidden Spin
Light can exhibit different kinds of rotational behavior. An optical vortex, for example, has a wave pattern that twists around its direction of travel, much like a corkscrew. Light also has a property known as polarization, which describes how its electric field oscillates. Certain polarization patterns produce a form of rotation called spin.
Physicists have long studied the relationship between these two properties. However, the interactions responsible for the newly observed effect were generally considered extremely weak and difficult to detect without specialized experimental conditions.
The researchers found that the situation changes when a beam of light is prepared in a particular balanced configuration.
Under those conditions, the beam can initially have no spin, yet distinct regions with spinning behavior emerge as it travels through free space. The effect does not require the light to pass through engineered materials or additional optical devices.
“It starts off with no spin at all,” explained MSc student Light Mkhumbuza, who carried out key experiments. “But as the beam travels forward, spinning regions appear and separate out — almost as if the spin was hiding and then revealed itself.”
Rather than creating spin through an external optical component, the researchers demonstrated how the beam’s existing internal structure can determine where spinning regions develop during propagation.
The Hidden Geometry That Controls Light
To explain this unexpected behavior, the researchers turned to topology, a mathematical field concerned with properties that remain unchanged when objects are continuously stretched, bent, or reshaped.
Dr. Isaac Nape, from the University of the Witwatersrand in Johannesburg, South Africa, offered a simple way to understand the concept.
“To explain it, imagine a mug and a doughnut,” he said. “You can morph one into the other without tearing it, because they both have one hole. That hole is a topological feature.”
The researchers found that structured light possesses its own topological characteristics, encoded in the arrangement of its polarization.
This underlying pattern acts like a mathematical fingerprint. Even as the light beam changes shape while traveling, its topological structure remains, influencing how different regions of the beam evolve.
As a result, the arrangement of the light itself can determine where its left-handed and right-handed spinning patterns become visible.
The discovery gives scientists a way to guide this behavior by designing the beam’s initial structure, rather than depending on specialized materials to produce the desired effect.
“This gives us a completely new tuning knob for light. By adjusting its topology, we can decide how and where chirality appears,” said Dr. Nape.
Potential Breakthroughs in Medicine and Communications
The ability to control light through its geometry could eventually make several important optical technologies simpler, more affordable, and more versatile.
One particularly promising application involves medical diagnostics and pharmaceutical research. Because many biologically important molecules have left-handed and right-handed forms, carefully structured light could help scientists identify these differences with greater sensitivity. Such tools could be valuable for evaluating drug safety and detecting biological markers associated with disease.
The same principles could support smaller optical sensors capable of identifying chemicals or biological substances without requiring large, sophisticated laboratory instruments.
Communications technology could also benefit. By encoding information into different twisting and spinning patterns, researchers may be able to increase the amount of data carried by individual light beams. This could contribute to faster optical communications, improved information security, and future quantum networks.
Other potential uses include manipulating microscopic particles, cells, and molecules with light, as well as developing more resilient quantum systems. Topological properties may help protect delicate quantum information against certain forms of noise and interference.
“The implications are wide-ranging,” said Dr. Forbes. “This work could lead to simpler and more sensitive medical tests, especially in drug development.
“It could also be used to pack more information into laser beams — boosting data capacity for communications, including future quantum networks.
“And because the effect doesn’t rely on fragile materials or precision-engineered surfaces, it could be easier and cheaper to use in real-world technologies.
“This research could lay the foundations for a new generation of light-based technologies, by showing that light’s behavior can be controlled using its own internal geometry,” he added.
These applications remain possibilities for future development, but the underlying discovery provides researchers with another way to design and control the behavior of light.
A Hidden Property of Light Finally Revealed
For decades, scientists have relied on increasingly sophisticated optical equipment to produce and manipulate unusual forms of light. The findings suggest that some of these behaviors can instead arise from carefully designed structures already encoded within a light beam.
By showing how topology governs the emergence of spinning regions during propagation, the team has revealed a previously underappreciated connection between light’s geometry and its physical behavior.
The discovery also illustrates how much remains to be learned about something as familiar and extensively studied as light.
“For something so familiar, light is proving to be far richer, stranger and more powerful than anyone imagined,” said Dr. Forbes.
“And astonishingly, this new behavior has been there all along — just waiting to be seen.”
The research, ‘Topological Control of Chirality and Spin with Structured Light’, was published in the journal Light: Science & Applications.
