Honest-to-God Holograms Will Use Sound to Shape Light

Holographic videos are a hallowed part of our conception of the future, and a mainstay of science fiction. An ersatz version of the technology has even allowed concert goers to be experience posthumous performances of celebrities like Tupac Shakur or Freddie Mercury.

Though these optically reincarnated celebrities aren't actually holograms, it might not be too long until genuine holographic video reaches the public, according to a study published today in the Review of Scientific Instruments. Led by electrical engineer Daniel Smalley, founder of the Electro-Holographic Research Group, the study proposes using acoustic waves to sculpt light into ideal angles and color compositions.

To create a hologram, engineers have to meticulously plan out how to diffract light into paths and patterns that will amount to a 3D image that can be viewed from multiple angles. Creating holographic videos further complexifies the process, because it requires a constantly changing set of parameters that add up to animated motion.

It turns out that sound waves can efficiently guide light along the precise yet complex paths needed to generate realistic holograms. This concept has been around for well over a decade now, and was developed into a prototype video display called the Mark-II by MIT professor Stephen Benton.

A video demonstration of Mark-II. Credit: Ikua Nakamura/Vimeo

But Smalley has built on the Mark-II by swapping out the Mark-II's tellurium dioxide crystals for lithium niobate crystals, which have flexible optical properties enabling much higher resolution.

The lithium niobate contain microscopic pathways that direct light through the crystal, called "waveguides." Smalley and his colleagues attached a tiny electrode to each waveguide that produces certain sound wave frequencies that shape light waves passing through the crystal into highly resolved colors and combinations. They are capable of updating at 30 frames a second, thus producing holographic motion.

"What's most exciting about [the new chip] is that it's a waveguide-based platform, which is a major departure from every other type of spatial light modulator used for holographic video right now," Smalley told Photonics.com in 2013, when he first announced the technique. Today's study provides a full overview of the apparatus.

"One of the big advantages here is that you get to use all the tools and techniques of integrated optics," he added. "Any problem we're going to meet now in holographic video displays, we can feel confident that there's a suite of tools to attack it relatively simply."

Smalley's work, in conjunction with the invention of a "trixel"—a 3D pixel—by an Austrian team of engineers, suggests that true holographic images and videos are finally on the horizon. The so-called "television renaissance" of recent years is defined by morally and intellectually multi-dimensional characters. It's only fitting that they gain a new visual dimension next.