Two Holograms in One Surface

Nanoscale silicon posts can reflect light differently depending on the angle of incoming light.


Scientists at the Caltech have recently discovered a way to encode more than one holographic image in a single surface without any loss of resolution. The building accomplishment upsets a long-held supposition that a solitary surface could just extend a solitary picture paying little respect to the edge of the light.

The innovation basically relies on the capacity of a deliberately built surface to ponder light distinctively depending the edge at which approaching light strikes that surface.

Two Holograms in One Surface
(Artist’s rendering) In a proof-of-concept, Faraon’s team encoded two holograms (of the Caltech logo and the LMI logo) on a single silicon oxide and aluminum surface
Credit: Andrei Faraon/Caltech

Holograms are three-dimensional pictures encoded on two-dimensional surfaces. At the point when the surface is lit up with a laser, the picture appears to fly off the surface and winds up plainly obvious. Customarily, the edge at which laser light strikes the surface has been unimportant—a similar picture will be obvious notwithstanding. That implies that regardless of how you enlighten the surface, you will just make one hologram.

Under the guidance of Andrei Faraon, assistant professor of applied physics and materials science, scientists developed silicon oxide and aluminum surfaces studded with tens of millions of tiny silicon posts, each just hundreds of nanometers tall.

Each nnano postreflects light contrasting because of varieties in its shape and measure, and in light of the edge of approaching light.

Faraon (BS ’04), senior author of a paper said, “Each post can do double duty. This is how we’re able to have more than one image encoded on the same surface with no loss of resolution.”

Two Holograms in One Surface
Nanoposts of varying shapes can act as pixels in two different holograms.
Credit: Andrei Faraon/Caltech

“Previous attempts to encode two images on a single surface meant arranging pixels for one image side by side with pixels for another image. This is the first time that we’re aware of that all of the pixels on a surface have been available for each image.”

That last property enables each post to go about as a pixel in more than one picture: for instance, going about as a dark pixel if approaching light strikes the surface at 0 degrees and a white pixel if approaching light strikes the surface at 30 degrees.

Scientists designed and built a surface that when illuminated with a laser straight on (thus, at 0 degrees) projects a hologram of the Caltech logo but when illuminated from an angle of 30 degrees projects a hologram of the logo of the Department of Energy-funded Light-Material Interactions in Energy Conversion Energy Frontier Research Center, of which Faraon is a principal investigator.

Kamali, the first author said, “The process was labor intensive. We created a library of nanoposts with information about how each shape reflects light at different angles. Based on that, we assembled the two images simultaneously, pixel by pixel.”

“Theoretically, it would even be possible to encode three or more images on a single surface—though there will be fundamental and practical limits at a certain point. For example, Kamali says that a single degree of difference in the angle of incident light probably cannot be enough to create a new high-quality image.”

“We are still exploring just how far this technology can go.”

Down to earth applications for the innovation incorporate enhancements to virtual-reality and expanded reality headsets. We’re as yet far from seeing this available, yet it is an essential exhibit of what is conceivable.

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