Scientists at the University of East Anglia have uncovered a hidden property of light that allows it to twist, spin and behave differently - without mirrors, materials or special lenses.

In a breakthrough that could transform medical testing, data transmission and future quantum technologies, researchers from the UK and South Africa have shown that light can be “programmed” simply by exploiting its natural geometry.

The discovery overturns decades of scientific thinking and reveals that light can develop chiral behaviour - meaning it can act like a left or right hand - while travelling freely through space.

This, the team says, could ultimately lead to a world where light carries information, probes biology, manipulates matter and protects quantum signals.

Why ‘handed’ light matters

Chirality, or “handedness”, is a crucial concept in science. Many molecules, including those used in medicines, come in left and right-handed forms that look almost identical but can behave very differently inside the human body.

To tell them apart, scientists often use special forms of light that spin either clockwise or anticlockwise. Until now, creating and controlling this kind of light required carefully engineered surfaces, exotic materials or extreme focusing using powerful lenses.

But the new study shows that none of that is necessary.

“Our work shows that light can naturally develop this handed behaviour 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.

Light that twists like a corkscrew

“Most people think of light as travelling 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 polarised. This spin can be left-handed or right-handed - another form of chirality.”

A hidden feature finally revealed

Until now, interactions between the spin and twist of light were thought to be incredibly weak - so weak that they could only be detected under special conditions.

But the UEA team found that if light is prepared in a carefully balanced state, its spin can appear naturally as it moves through empty space.

“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.”

No mirrors. No special materials. Just light propagating freely.

The ‘topological fingerprint’ of light

According to Dr Isaac Nape, at the University of the Witwatersrand in Johannesburg, South Africa, the reason this happens lies in topology - a branch of maths that focuses on properties that stay the same, even when objects are stretched or reshaped.

“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.”

Light, it turns out, has its own version of this “hole count” - a hidden topological fingerprint buried in the way its polarisation is arranged. This fingerprint doesn’t disappear as light travels. Instead, it quietly guides how the beam evolves.

As the light moves forward, the hidden structure forces the spinning behaviour to emerge - giving scientists a powerful new way to control light using geometry alone.

“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.

Wide-ranging implications

“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 behaviour can be controlled using its own internal geometry,” he added.

Key future applications:

• Simpler medical and pharmaceutical tests, using specially structured light to distinguish left‑ and right‑handed molecules vital for drug safety and disease detection.
• Compact optical sensors capable of identifying biological and chemical substances quickly, cheaply and without laboratory‑grade equipment.
• More powerful communication technologies, where information is packed into multiple twisting and spinning states of light to boost data capacity and security.
• Advanced tools for biology and nanotechnology, allowing tiny particles, cells or molecules to be moved and rotated using light alone.
• More robust quantum technologies, with topology helping protect delicate quantum information from noise and disruption.

A quiet revolution in plain sight

The researchers say their work challenges long-held assumptions about what light can and cannot do on its own.

“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 behaviour has been there all along — just waiting to be seen.”

‘Topological Control of Chirality and Spin with Structured Light’ is published in the journal Light: Science & Applications.