Light-bending metasurfaces open new opportunities in advanced imaging, display
Magic Leap is working on a head-mounted virtual retinal display that superimposes 3D computer-generated imagery over real-world objects by projecting a digital light field into the user’s eye, allowing virtual imagery to coexist and interact with a viewer’s actual surroundings in real time. The latest achievement uses silicon-based, ultrathin optical components to enable the manipulation of light over wide angles, and across the visible light spectrum, in a very efficient way.
“We are now able to create silicon surfaces that can take in light from a large number of input angles and wavelengths with minimal loss of diffraction efficiency,” says Stefano Cabrini, director of the Nanofabrication Facility at Berkeley Lab’s Molecular Foundry. “The input flexibility and the degree of control these nanostructures have over the output beam has never been seen before.”
Such nanoscale manufactured optical devices could, say the researchers, usher in a new generation of affordable devices with advanced functionality for telecommunications, medicine, and consumer products. Potential applications include smart surfaces that can repel fluids, ultrafast data processing, holograms, and even “invisibility” cloaks that can conceal objects by manipulating light.
The new technology uses “optical metasurfaces” – 2D structures designed to interact with light waves in ways that natural materials cannot. Ultrathin and able to be integrated into a variety of systems, the materials can have layers that are a few nanometers thick, and contain nanoscale optical antennas that can control the reflection or transmission of light.
The metasurfaces were created by carving a pattern of silicon nanobeams – arranged to control either the transmission or reflection of light – using a focused beam of electrons and then transferring the design onto an ultrathin layer of silicon. By making the metasurfaces out of silicon, the researchers were able to take advantage of widely available fabrication technology, which also allows the devices to be more easily scaled up to mass production.
Founded in 2010, Magic Leap has not yet released a product to the market. This latest research may provide a hint at what technology will be incorporated in any eventual AR glasses from the company.
For more, see “Optical metasurfaces for high angle steering at visible wavelengths.”
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