Holograms Created with New Technique to Increase Variety

Scientists have developed new techniques in order to create a new variety of holograms. The new methods can be used to create idea geometric phase holograms for any kind of optical pattern, which is a significant advance over the limitations of previous techniques.

A geometric phase hologram is a thin film that manipulates light. Light moves as a wave, with peaks and troughs. When the light passes through a geometric phase hologram, the relationship between those peaks and troughs is changed. By controlling those changes, the hologram can focus, disperse, reorient or otherwise modify the light.

An ideal geometric phase hologram modifies the light very efficiently. This means that little of the light is wasted. However, ideal geometric phase holograms also produce three different, well-defined "wavefronts," or transformed versions of the light that passes through the thin film.

"We can direct light into any one or more of those three wavefronts, which allows us to use a single ideal geometric phase hologram in many different ways," said Michael Escuti, one of the researchers, in a news release. "We've come up with two ways of making ideal geometric phase holograms that are relatively simple but allow us to control the orientation of the molecules that ultimately manipulate the light."

The researchers first used lasers to create a high-fidelity light pattern. A photoreactive substrate records the light pattern, with each molecule in the substrate orienting itself depending on the polarization of the light it was exposed to. The pattern that is recorded then serves as a template for a liquid crystal layer that forms the finished hologram.

"Using these techniques, we're above to create ideal geometric phase holograms in nearly any pattern," said Escuti. "Theoretically, there are patterns that are too small for us to make, but we've been able to make these patterns for every practical application we've addressed so far-from astronomical instruments to art installations."

The findings are published in the journal Optica.

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