Researchers at Stanford University have developed a nanodevice that uses high-frequency acoustic waves to control light at the nanometer scale. The team, led by Mark Brongersma, professor of materials science and engineering, and doctoral candidate Skyler Selvin, described their work in the journal Science.
The device consists of a thin gold mirror coated with an ultrathin layer of silicone-based polymer. Gold nanoparticles are arranged on top of this polymer layer. By attaching an interdigitated transducer (IDT) to the side, the researchers generate surface acoustic waves that move across the film at nearly a billion times per second. These sound waves cause the gold nanoparticles to oscillate above the gold mirror.
When light is shined into the system, it is confined in the tiny gaps between each nanoparticle and the mirror. The size of these gaps—controlled by adjusting the acoustic waves—determines both the color and intensity of light emitted from each nanoparticle.
“In optics, big equals slow,” Brongersma said. “So, this device’s small scale makes it very fast.”
Selvin added, “In this narrow gap, the light is squeezed so tightly that even the smallest movement significantly affects it. We are controlling the light with lengths on the nanometer scale, where typically millimeters have been required to modulate light acoustically.”
Brongersma noted his surprise at how effective small changes were in altering light properties: “I was rolling on the floor laughing. I thought it would be a very subtle effect, but I was amazed how much nanometer changes in distance can change the light scattering properties so dramatically.”
The research could lead to advances in several fields such as ultrathin video displays, improved holographic virtual reality headsets, 3D holographic imagery, optical communications and new types of ultrafast neural networks using light instead of electricity.
“When we can control the light so effectively and dynamically,” Brongersma said, “we can do everything with light that we could want – holography, beam steering, 3D displays – anything.”
Other contributors include former postdoctoral scholar Majid Esfandyarpour; PhD students Anqi Ji, Yan Joe Lee and Colin Yule; research scientist Jung-Hwan Song; and postdoctoral scholar Mohammad Taghinejad. Brongersma is also affiliated with Stanford Bio-X, Wu Tsai Human Performance Alliance and Neurosciences Institute as well as being an affiliate of Precourt Institute for Energy.
The study received funding from both the Department of Energy and Meta Platforms Inc.
