Heriot-Watt team’s breakthrough makes light work of electromagnetic waves
Scientists at Heriot-Watt University have demonstrated what they describe as a world first in photonics research, using light itself to control how electromagnetic waves oscillate at ultra-fast speeds.
The breakthrough, published in Nature Photonics, centres on the control of polarisation, a fundamental property of light that influences how it interacts with materials and carries information. Researchers say the work overcomes a long-standing challenge in photonics by achieving a level of control that is both sufficiently fast and sufficiently strong for practical systems.
The study, titled 'All-optical polarization control in time-varying low index films via plasma symmetry breaking', was led by researchers at Heriot-Watt’s Institute of Photonics and Quantum Sciences alongside collaborators from Purdue University, the University of Brescia and the University of L’Aquila.
Dr Marcello Ferrera, of the School of Engineering and Physical Sciences, said controlling how light oscillates directly affects how it interacts with matter.
“How light oscillates has a huge impact on how it interacts with the physical world around us,” he explained. “For the first time, we now have full control over this property of light, for any polarisation state, and at ultra-fast speeds.”
To achieve this, the team designed an experiment using a thin transparent film made from aluminium zinc oxide, already used in applications such as touchscreens and solar panels. Under normal conditions, the material behaves similarly to glass. However, researchers exposed it to an engineered burst of light lasting less than a trillionth of a second.
During that brief interval, a second pulse of light passing through the film could have its oscillation behaviour controlled by the first pulse. According to the researchers, the initial pulse effectively “programmes” the second one, determining how it subsequently interacts with materials.
Crucially, the process relies entirely on light rather than electronics or moving mechanical components. The team says this enables changes to occur around 10,000 times faster than current state-of-the-art electronic approaches, while producing effects approximately 100,000 times stronger than previously recorded.
The work could represent an advance in time-varying photonics, where the properties of materials are deliberately altered while light is travelling through them.
Professor Ferrera said this differs fundamentally from most conventional photonics research, where materials remain static during light transmission.
“What makes this different is that the material itself is changing while the light is travelling through it,” he said. “That may sound subtle, but it fundamentally changes how we can manipulate light.”
Potential applications range from advanced medical diagnostics and drug development through to quantum technologies. The researchers note that polarised light is already used in pharmaceutical synthesis to distinguish between mirror-image molecules that can produce very different biological effects.
The findings may also have implications for quantum computing and secure communications systems, where information can be encoded in the polarisation state of light.
Professor Ferrera added that time-varying systems had largely remained a theoretical concept for decades, but that the latest results demonstrate their practical feasibility.
“This now opens up entirely new possibilities for future medical tools and next generation quantum technologies which have been held back by this limitation previously,” he said.
