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New Metahologram Design Created

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A multifunctional meta-hologram design, developed by researchers at Pohang University of Science and Technology (POSTECH), can be used to create different hologram images depending on the direction of the incident light that falls on the device. Conventional meta-holograms can display images when the incident light falls in one direction only. The POSTECH meta-hologram was created from a monolayer meta-holographic optical device.

To design directional sensitivity into their meta-hologram, the researchers included direction-controlled, spin-dependent holographic recordings in the monolayer structure. The metasurface hologram they designed consists of nano half-waveplates of low-loss, hydrogenated amorphous silicon. The half-waveplates are designed and optimized for circularly polarized illumination, and can excite electric and magnetic resonances simultaneously, as well as antiferromagnetic modes, to ensure high transmission for the cross-circularly polarized light. The dual magnetic and antiferromagnetic resonances make the device more efficient than a conventional meta-hologram.

The new meta-hologram demonstrated a diffraction efficiency higher than 60% with clear, high-quality images. Because silicon is used to make the meta-hologram, it can be easily produced through a conventional semiconductor manufacturing process.

Meta-hologram optical device that operated in forward and backward directions. Courtesy of Junsuk Rho(POSTECH)

Meta-hologram optical device that operates in forward and backward directions. Courtesy of Junsuk Rho (POSTECH).

The researchers believe that their meta-hologram, which operates in forward and backward directions, could be the basis for a new hologram platform that could transmit information to multiple users from different locations, overcoming the limits of conventional meta-holograms, which can only transmit one image to a limited number of locations.

“A microscopic, ultrathin, ultralightweight, flat optical device based on a metasurface is an impressive technique with great potential, 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,” professor Junsuk Rho said. “We developed a meta-hologram optical device that operates in forward and backward directions and that can 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.”

The research was published in Nanoscale Horizons (www.doi.org/10.1039/C9NH00460B). A correction to the paper was also published (www.doi.org/10.1039/D0NH90006K).

Photonics Spectra
Apr 2020
GLOSSARY
multiplexing
The combination of two or more signals for transmission along a single wire, path or carrier. In most optical communication systems this is referred to as wavelength division multiplexing, in which the combination of different signals for transmission are imbedded in multiple wavelengths over a single optical channel. The optical channel is a fiber optic cable or any other standard optical waveguide.
holography
The optical recording of the object wave formed by the resulting interference pattern of two mutually coherent component light beams. In the holographic process, a coherent beam first is split into two component beams, one of which irradiates the object, the second of which irradiates a recording medium. The diffraction or scattering of the first wave by the object forms the object wave that proceeds to and interferes with the second coherent beam, or reference wave at the medium. The resulting...
Research & TechnologyeducationAsia-PacificPohang University of Science and Technologyimaginglight sourcesmaterialsopticsDisplayshologramsmeta-hologramsmetasurfacesmultiplexingholographyCommunicationsTech Pulse

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