Pixels control and analyze light on displays—they’re part of the reason you’re reading this sentence right now. But it’s typically one or the other. A pixel either controls or analyzes, but not at the same time.
Researchers from ETH Zurich in Switzerland, however, managed to create a new type of pixel that can simultaneously do both. This hypercharged pixel, called a Fourier pixel, can generate and sense arbitrary light fields and tap into a pixel’s full potential for carrying information by manipulating light’s intensity, oscillation phases, and polarization. The team reported its findings in a paper published yesterday in Nature.
Looking ahead, the team anticipates these pixels could support next-generation technologies such as holographic displays, augmented reality, or devices that can actively correct their output based on what they detect. The technology could also pave the way for camera–display devices that both display images and sense incoming light.
“A Fourier pixel expands the functionality of conventional pixels by exploiting surface waves that interact with a precisely designed wavy microstructure,” study co-authors Yannik Glauser and Sander Vonk told Gizmodo. “In this sense, it is not just an intensity pixel but a compact optical element for full-field light control.”
“This ability is important because light can carry a lot of information if we can completely control all of its attributes,” added David Norris, the study’s co-author and an optical physicist who led the team.
Unlocking light’s potential
Currently, pixels—short for “picture elements”—locally measure or emit light intensity, working only with one property of light, according to the paper. But in recent years, researchers have explored ways to tamper with varying properties of light in the search for next-generation information technologies, such as Microsoft’s Project Silica.
“As optical technologies become more advanced, whether in displays, sensing, communication, or imaging, we will need devices that can handle the full complexity of light,” explained Glauser and Vonk, a doctoral student and postdoctoral researcher in optics, respectively. Fourier pixels, which offer bidirectional control of light, represent one step in that direction, they added.
Ripples of the light
Fourier pixels are built on several basic phenomena in optical physics. They’re called that because the mathematical principles at play were devised by mathematician Joseph Fourier, explained Norris. In previous work, the team had come up with a technique to create arbitrarily wavy surfaces based on Fourier’s work.
This was a key component of Fourier pixels, Norris added, as they hinted to the team that there was a way for precisely engineered surfaces to interact with the various properties of light. For the latest results, the researchers expanded upon this idea. Specifically, they tested if these scattered lightwaves could be converted into guided waves and into an optical pattern that carries relevant information.
In other words, the pixel—here, the sculpted part of an interface—can both generate and sense the key properties of light (amplitude, oscillation phases, and polarization) to represent images or information. What’s more, designing these pixels requires relatively simple mathematics, which makes them “flexible and convenient for potential applications,” Norris said.
Pixels of the future
According to a university statement, Fourier pixels could contribute to two-way camera displays, in which each pixel both emits and detects light. To Gizmodo, Glauser and Vonk explained that these next-generation devices “could not only show an image but also sense how light from the environment or a user interacts with it.”
For the latest work, the team succeeded in creating very small arrays of Fourier pixels, Norris admitted, adding that such camera displays at the moment are in the realm of speculation. But it’s a fascinating step in an unexplored direction. In theory, Fourier pixels could come in handy in designing “adaptive optics, holographic displays, augmented reality, optical communication, or devices that actively correct their output based on what they detect,” said Glauser and Vonk.
“Personally, I find the combination of simple math and precise fabrication extremely beautiful,” Norris said. “The math predicts some crazy wavy pattern for a specific optical output. We go and make that pattern on the surface and the device immediately creates the output that we want. In other words, math really works!”
