OLEDs may be the key to holography

Imagine sitting in your living room, and instead of pulling up a flat screen, you switch on a device the size of a matchbox. A crisp holographic image appears in midair, a lifelike projection that feels pulled straight from science fiction.

That vision just came a little closer to reality, thanks to new research from the University of St Andrews in Scotland. In a paper published in Light: Science & Applications, physicists Junyi Gong, Mohammad Biabanifard, Kou Yoshida, Graham A. Turnbull, Andrea Di Falco, and Ifor D. W. Samuel unveiled a compact way to project holographic images using something already inside your smartphone: OLEDs.

If you own a modern smartphone or television, you’re already familiar with OLEDs, or organic light-emitting diodes. These ultra-thin, flexible, and energy-efficient light sources are made from carbon-based materials. They’re widely used in consumer electronics because they produce vivid colors while being lightweight and relatively simple to manufacture.

OLEDs do have limitations, however. Unlike lasers, which emit a highly focused, coherent beam of light, OLEDs produce light in a more scattered, less orderly way. That makes them ideal for screens but less suited to applications like holography, which require precise control of light waves to form detailed three-dimensional images.

Enter the metasurface

This is where metasurfaces come in. These are extremely thin materials patterned with nanoscale structures that can bend, twist, and shape light in ways ordinary lenses cannot. Rather than simply allowing light to pass through, a metasurface actively directs it.

Metasurfaces are already being explored for augmented reality glasses, advanced microscopes, and even security features on banknotes. Most of these uses, however, rely on lasers, precisely because of the coherence they provide. Using something as scattered as OLED light for holograms once seemed impossible.

The St Andrews team asked: what if an OLED could be paired with a metasurface to project holographic images, without lasers?

Their solution was a working prototype made up of three parts: an OLED, a bandpass filter, and a specially designed metasurface. The OLED supplied the light, the filter narrowed the color range to improve clarity, and the metasurface sculpted the light into an image.

In one demonstration, the researchers used a red-emitting OLED and a metasurface patterned to project the image of a Dalmatian dog. Initially the projection was blurry, a reflection of OLEDs’ limitations. But with the addition of a filter that trimmed the color spectrum, the image sharpened dramatically, revealing clear features of the dog.

Just as important, the setup was compact. The OLED and metasurface needed only 3 to 6 centimeters of separation, making the system small enough to imagine being built into everyday devices.

You might wonder why this is necessary when projectors and screens already exist. The advantages lie in the unique qualities of OLEDs and metasurfaces.

Unlike bulky laser projectors, this system is lightweight and compact enough to fit in a pocket. OLEDs are safer and cheaper than lasers, which can be hazardous to the eye and costly to manufacture. They can also be made on flexible substrates, opening the door to wearable holographic displays.

Together, these qualities hint at a future where holography is not confined to science fiction but used in daily life: AR headsets that project images directly into view, portable projectors that display holograms on any surface, or smart devices that communicate through floating, interactive visuals.

One of the clever solutions proposed in the study was tackling the “coherence problem.” Lasers emit neat, ordered waves of light, while OLEDs emit more chaotic ones. To address this, the researchers adjusted the distance between the OLED and the metasurface. Moving the OLED slightly farther back improved the coherence of the light, sharpening the image.

It’s similar to adjusting the focus of a flashlight: set the distance just right, and the beam appears cleaner. Combined with color filtering, the result was an image that rivaled what you might expect from a laser-based setup, but created with everyday OLED technology.

The prototype remains a proof of concept. The images were dimmer than those from laser systems, and the setup required an external filter. Still, the potential is significant. With further refinements, such as integrating filters directly into the OLED or metasurface, or fabricating metasurfaces from inexpensive polymers, this approach could leap toward mass-produced holographic displays.

The implications range from video calls where the caller appears as a hologram to interactive 3D maps manipulated by hand. This research points to a future where holography becomes a practical, widely used technology.

What makes this study compelling is the fact that the same OLED technology already present in billions of devices could be repurposed to create holographic displays, without the need for bulky lasers. This opens the door to a new kind of display technology, one that could make holograms an ordinary part of our visual world.

If you want to learn more, read the original article titled "OLED illuminated metasurfaces for holographic image projection" on Light: science & applications at http://dx.doi.org/10.1126/scirobotics.adl2976.