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Thursday, 13 February 2020

As seen in Movies, Holograms can be used as a communication tool

For the time being the team has only managed to transmit letters and small messages, but the future is promising, as seen in this art. [Image: Nanoscale Horizons]


Those who  have watched the film Black Panther saw people from the Wakanda Kingdom communicating through holograms. And that specific scene of fiction can become a reality sooner than you might imagine, allowing you to exchange different information with people from different locations.

This possibility is being made possible by the creation of "meta-holograms", which are modified versions of the same holograms used to prevent counterfeiting, in notes and credit cards.

The difference is that the meta-holographic structures are capable of showing one image when the incident light is in one direction, and another different image when the light is coming from the other direction.

In addition, the meta-holograms created now by a team at Pohang University in South Korea are thin and light, making them easier to apply in practice - they fall into the field of metamaterials , the same ones that manipulate light to create the mantles of invisibility.



Televisions and beam projectors can only transmit intensity of lights but holographic techniques can save light intensity and its phase information to play movies in three-dimensional spaces. At this time, if metamaterials are used, a user can change nano structures, size, and shapes as desired and can control light intensity and phase at the same time. Meta-hologram has pixel sizes as small as 300 to 400 nanometers but can display very high resolution of holographic images with larger field of view compared to existing hologram projector such as spatial light modulator.

Device illustration (left) and real images transmitted to one side and the other (right) - consider that the meta-surface is in the center of the black square.

To get ahead, the team used two different types of meta-surfaces - essentially flat metamaterials. The first meta-surface was designed to have phase information when the incident light is in the "forward" direction, while the other operates when the light is in the "back" direction.

As a result, different images are displayed in real time, depending on the direction of the light - or, in other words, transmitting different information to different locations.

In addition, the team applied dual magnetic resonances and antiferromagnetic resonances, which are phenomena occurring in silicon nanopillars, to nanostructure design to overcome low efficiency of the conventional meta-hologram. This newly made meta-hologram demonstrated diffraction efficiency higher than 60% (over 70% in simulation) and high-quality and clear images were observed.

Furthermore, the new meta-hologram uses silicon and it can be easily produced by following through the conventional semiconductor manufacturing process.



Junsuk Rho who is leading research on metamaterials said, 'Microscopic, ultrathin, ultralightweight flat optical devices based on a metasurface is an impressive technique with great potentials as it can not only perform the functions of the conventional optical devices but also demonstrate multiple functions depending on how its metasurface is designed. Especially, we developed a meta-hologram optical device that operated in forward and backward directions and it could transmit various visual information to multiple users from different locations simultaneously. We anticipate that this new development can be employed in multiple applications such as holograms for performances, entertainment, exhibitions, automobiles and more."


Bibliography:

Article: Engineering spin and antiferromagnetic resonances to perform an efficient direction-multiplexed visible meta-hologram

Authors: Muhammad Afnan Ansari, Inki Kim, Ivan D. Rukhlenko, Muhammad Zubair, Selcuk Yerci, Tauseef Tauqeer, Muhammad Qasim Mehmood, Junsuk Rho

Magazine : Nanoscale Horizons

DOI: 10.1039 / D0NH90006K

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