Holograms — three-dimensional images formed by the interference of light beams — have been around for quite some time. They can be created with magnetic fields, and they have potential applications in autonomous vehicle sensors, space communications and optical wireless networks.
So why is it that we generally see them only in science-fiction films like Star Wars? The rare-earth materials used to create them are expensive, brittle and opaque. Some will work only in temperatures as cold as the vacuum of outer space.
Yet researchers from the University of Michigan and the Federal University of São Carlos (UFSCar) have demonstrated an approach to create holograms at room temperature using an inexpensive nanoparticle gel. This could enable mass-market 3D displays, holographic projectors and a new generation of light detection and ranging (LIDAR) — one of the key technologies that gives “sight” to autonomous vehicles.
In a paper published in Science, the researchers show how nanoparticles based on cobalt oxide, a white-colored, magnetic semiconductor, can be suspended in a transparent, elastic, room-temperature gel and used to control circularly polarized light — in essence, “twisted” light. The trick, the researchers found, is to twist the nanoparticles themselves, by coating them with amino acids. This produces a heightened sensitivity to magnetism and strengthens the interaction to light, allowing the application of a magnetic field to change the light’s intensity.
“This opens the road to the wide proliferation of magneto-optical devices with exciting possibilities emerging in 3D displays and real-time holography — all utilizing circularly-polarized light,” says Nicholas Kotov, a chemical engineering professor at Michigan. “Furthermore, the small size of the nanoparticles enables their use in computer engineering and large-scale manufacturing of magneto-optical composites.”
The University of Michigan is currently pursuing patent protection for the intellectual property, and seeking commercialization partners to help bring the technology to market.