When we look at the world around us, all that we see is thanks to light. It reflects, refracts, and interacts, carrying shape and depth from the objects it touches.
But what about light itself?
Physicists have now visualized the simulated shape of a photon (the smallest unit of light) emitted from the surface of a nanoparticle using a novel theoretical model. These findings offer new insights into how light behaves, potentially paving the way for innovations in nanophotonics and quantum technology.
“We were able to produce this image of a photon, something that hasn’t been seen before in physics,” said theoretical physicist Ben Yuen, lead author of the study.
What Does a Photon Look Like?
The visualization, produced by researchers at the University of Birmingham, is not a photograph; you can’t simply photograph a photon. Instead, it’s a detailed simulation derived from quantum calculations. “Our calculations enabled us to convert a seemingly insolvable problem into something that can be computed,” said Dr. Yuen. “And, almost as a by-product of the model, we were able to produce this image of a photon, something that hasn’t been seen before in physics.”
The “shape” of a photon, as physicists define it in this case, is an intensity distribution—a map of where the photon is most likely to be found at a given moment. Brighter regions indicate areas where the photon is more likely to appear. Dr. Yuen explained further for New Atlas: “Because it’s a quantum particle, you cannot measure it in one go as the measurement destroys it. However, if you were to repeat the measurement many times, you would see exactly this distribution.”
This achievement required a profound leap in quantum field theory, combining complex analysis and nanoparticle interactions. By simulating a photon emitted from an atom sitting on a silicon nanoparticle, the researchers highlighted an important observation: the environment profoundly shapes the photon. The nanoparticle, for example, made the photon thousands of times more likely to be emitted and even allowed it to be reabsorbed by the atom multiple times.
Why Does It Matter?
By better understanding the fundamental interactions between light and matter, scientists can design advanced technologies. The findings could be useful in fields ranging from quantum computing to renewable energy. “By understanding this, we set the foundations to engineer light-matter interactions for future applications,” said Yuen. “Think better sensors, improved photovoltaic energy cells, or quantum computing.”
In quantum information systems, for example, the shape of a photon could determine how efficiently it carries data. In biological systems, it could help scientists understand how light drives chemical reactions like photosynthesis.
Traditionally, scientists model this interaction using simplified equations that treat light as moving through empty space or bouncing between mirrors in a cavity. These methods break down, however, when light interacts with complex materials—like nanoparticles, quantum dots, or biological molecules—where the geometry of the surroundings dramatically reshapes the photon itself.
“The geometry and optical properties of the environment has profound consequences for how photons are emitted, including defining the photon’s shape, color, and even how likely it is to exist,” said co-author Angela Demetriadou, a theoretical nanophotonics professor at Birmingham.
This means a photon doesn’t have a universal form. Each one is sculpted by the environment from which it emerges—its “body” molded by the surrounding electromagnetic fields. So every photon’s ‘shape’ will be different, depending on the materials with which it interacts.
In this case, Yuen and Demetriadou simulated a photon emitted from a silicon nanoparticle just one micrometer in diameter. The result was a lopsided, lemon-shaped structure—its asymmetry a direct imprint of how the particle’s surface influenced the quantum fields from which the photon was born.
“This is really the point of nanophotonics,” Yuen said. “By shaping the environment, we can really shape the photon itself.”
For a particle as elusive as the photon, this discovery is nothing short of illuminating.
The findings appeared in the journal Physical Review Letters.
This article originally appeared in November 2024 and was updated with new information.
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