True holograms – 3D images captured like photographs – are still a long way from replicating the flashy stage tricks that masquerade under the title. Although most holograms are still pretty tiny, a team from Australia's RMIT and the Beijing Institute of Technology (BIT) have created the world's thinnest holographic display, encoding a 3D image onto a material just 25 nanometers thick.
Holograms are created with lasers, by modifying a material so that different sections reflect light back in different phases, giving the viewer the illusion of depth. Normally, that requires the medium to be a certain thickness, usually on the scale of millimeters at least. But the researchers have managed to create a hologram on a surface 100 times thinner, using a material called a topological thin film insulator and a carefully-controlled laser.
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"We produced a new type of material, a topological insulator thin film, which means on the surface of this material, it behaves like a metal, and inside the material it's like an insulator, like plastic," lead researcher on the project, Min Gu, tells New Atlas. "We fire a laser into this material, and depending on the intensity of the laser, we can modify the properties of this material. That modulation gives us the capability to encode a hologram into such a thin film."
Not only does that technique allow for thinner surfaces to become holographic displays, but it allows them to create smaller pixels. By changing the spot size of the laser, the team says each pixel is currently about 100 nm, and that in turn allows the image to be seen more clearly from a wider range of angles.
"The size of the pixels determines the viewing angle," Gu says. "We can squeeze the laser beam down to a small region, and in fact our viewing angle is larger than the normal 3D display. With a usual 3D display, you wear glasses, and [you can see] plus or minus 10 degrees. In this paper, we demonstrated we can do up to 20 degrees viewing angle."
In future, the team plans to try to shrink the spot size, and as a result the pixels, down below 100 nm, which would allow them to encode more information into each hologram, and effectively create a higher definition image and a wider viewing angle.
"What we want to do in the next step is try to reduce the pixel size. That's an important step so many people are working on it, but we probably have an advantage because we know how to nano-engineer the beam."
With better definition, the system could eventually lead to films that layer 3D projections over 2D screens.
"The next stage for this research will be developing a rigid thin film that could be laid onto an LCD screen to enable 3D holographic display," Zengyi Yue, co-author of the paper, says in a statement. "But beyond that, we are looking to create flexible and elastic thin films that could be used on a whole range of surfaces, opening up the horizons of holographic applications."
The research was published in the journal Nature Communications and the team describes the hologram in the video below.