What technology is used to make holograms

Metastructure creates hologram videos

Star Wars sends its regards: Holographic videos will be easier to produce in the future - thanks to tailor-made nano columns and “corkscrew light”. Because through the combination of a metastructured surface and light with an orbital angular momentum, moving 3D images can not only be projected onto flat surfaces, they are also easier to digitize, as the researchers report in the specialist journal "Nature Nanotechnology".

Whether the holodeck from “Star Trek” or the holographic call for help from Princess Leia from “Star Wars”: video holograms have long been part of everyday life in fiction. But in reality, bulky devices, thick carrier materials and sequential scanning of holograms are necessary for this. Although some of these video holograms allow free-floating images and even a tactile impression, they only work within special boxes and are small and with low resolution.

Nanopillars manipulate the light

This could change now. Researchers working with Haoran Ren from the Ludwig Maximilians University in Munich have developed a process with which holographic videos can be produced on the basis of meta-surfaces - surfaces with a nanostructure that refracts the light in a special way. The result is ultra-thin, flat optics that influence the amplitude, phase and polarization of the light in such a way that a holographic visual impression is created.

Specifically, the hologram display consists of a meta-surface with hundreds of nano-polymer columns in different orientations and heights. This tailor-made nanostructure surface is produced simply with the help of a 3D printer, as the researchers explain.

Screwed light as a hologram carrier

In order to generate the hologram video, this surface is irradiated with “corkscrew light”. This light has an orbital angular momentum (OAM) that twists the light wave into a helical shape. This twisted light can then be used to transport information such as video data.

The big advantage: These "light screws" can encode and transport more data than conventional light signals. Because in addition to wavelength, polarization and angle of incidence, the orbital angular momentum can also encode information. “This degree of freedom of light has an unlimited number of special modes that can function as independent information channels,” explains Ren.

New applications for hologram videos

The researchers developed a meta-surface hologram with complex amplitude and phase control for their holography. “Our holographic technology, based on the orbital angular momentum, can distribute signals to up to 200 independent OAM channels,” explain Ren and his team. In a first test, the combination of meta-surface and corkscrew light produced hologram videos with around 100 individual images each and a resolution of 260 pixels per inch.

According to the scientists, this form of hologram displays opens up completely new possibilities: "Our 3D laser printing on meta-surfaces could inspire new types of meta-surface designs for a multitude of applications in which the current flat optics have a significant impact," says Ren's colleague Stefan Maier . They could enable holographic head-up displays, wearable devices for augmented reality and deep learning microscopy, among other things. (Nature Nanotechnology, 2020, doi: 10.1038 / s41565-020-0768-4)

Source: Ludwig Maximilians University of Munich

October 1, 2020

- Nadja Podbregar