Light can behave in very unexpected ways when you squeeze it into small spaces. In a paper in the journal Science, Mark Brongersma, a professor of materials science and engineering at Stanford University, and doctoral candidate Skyler Selvin describe the novel way they have used sound to manipulate light that has been confined to gaps only a few nanometers across—allowing the researchers exquisite control over the color and intensity of light mechanically.
The findings could have broad implications in fields ranging from computer and virtual reality displays to 3D holographic imagery, optical communications, and even new ultrafast, light-based neural networks.
The new device is not the first to manipulate light with sound, but it is smaller and potentially more practical and powerful than conventional methods. From an engineering standpoint, acoustic waves are attractive because they can vibrate very fast, billions of times per second.
Unfortunately, the atomic displacements produced by acoustic waves are extremely small—about 1,000 times smaller than the wavelength of light. Thus, acousto‑optical devices have had to be larger and thicker to amplify sound’s tiny effect—too big for today’s nanoscale world.
“In optics, big equals slow,” Brongersma said. “So, this device’s small scale makes it very fast.”
Simplicity from the start
The new device is deceptively simple. A thin gold mirror is coated with an ultrathin layer of a rubbery silicone‑based polymer only a few nanometers thick. The research team could fabricate the silicone layer to desired thicknesses—anywhere between 2 and 10 nanometers. For comparison, the wavelength of light is almost 500 nanometers tip to tail.
The researchers then deposit an array of 100‑nanometer gold nanoparticles across the silicone. The nanoparticles float like golden beach balls on an ocean of polymer atop a mirrored sea floor. Light is gathered by the nanoparticles and mirror and focused onto the silicone between—shrinking the light to the nanoscale.
To the side, they attach a special kind of ultrasound speaker—an interdigitated transducer, IDT—that sends high‑frequency sound waves rippling across the film at nearly a billion times a second. The high‑frequency sound waves (surface acoustic waves, SAWs) surf along the surface of the gold mirror beneath the nanoparticles. The elastic polymer acts like a spring, stretching and compressing as the nanoparticles bob up and down as the sound waves course by.
The researchers then shine light into the system. The light gets squeezed into the oscillating gaps between the gold nanoparticles and the gold film. The gaps change in size by the mere width of a few atoms, but it is enough to produce an outsized effect on the light.
The size of the gaps determines the color of the light resonating from each nanoparticle. The researchers can control the gaps by modulating the acoustic wave and therefore control the color and intensity of each particle.
“In this narrow gap, the light is squeezed so tightly that even the smallest movement significantly affects it,” Selvin said. “We are controlling the light with lengths on the nanometer scale, where typically millimeters have been required to modulate light acoustically.”
Starry, starry sky
When white light is shined from the side and the sound wave is turned on, the result is a series of flickering, multicolored nanoparticles against a black background, like stars twinkling in the night sky. Any light that does not strike a nanoparticle is bounced out of the field of view by the mirror, and only the light that is scattered by the particles is directed outward toward the human eye. Thus, the gold mirror appears black and each gold nanoparticle shines like a star.
The degree of optical modulation caught the researchers off guard. “I was rolling on the floor laughing,” Brongersma said of his reaction when Selvin showed him the results of his first experiments.
“I thought it would be a very subtle effect, but I was amazed at how many nanometer changes in distance can change the light scattering properties so dramatically.”
The exceptional tunability, small form factor, and efficiency of the new device could transform any number of commercial fields. One can imagine ultrathin video displays, ultra‑fast optical communications based on acousto‑optics’ high‑frequency capabilities, or perhaps new holographic virtual reality headsets that are much smaller than the bulky displays of today, among other applications.
“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.”
More information: Skyler Peitso Selvin et al, Acoustic wave modulation of gap plasmon cavities, Science (2025). DOI: 10.1126/science.adv1728. www.science.org/doi/10.1126/science.adv1728
Journal information: Science
Provided by Stanford University
News
Lab-grown corticospinal neurons offer new models for ALS and spinal injuries
Researchers have developed a way to grow a highly specialized subset of brain nerve cells that are involved in motor neuron disease and damaged in spinal injuries. Their study, published today in eLife as the final [...]
Urgent warning over deadly ‘brain swelling’ virus amid fears it could spread globally
Airports across Asia have been put on high alert after India confirmed two cases of the deadly Nipah virus in the state of West Bengal over the past month. Thailand, Nepal and Vietnam are among the [...]
This Vaccine Stops Bird Flu Before It Reaches the Lungs
A new nasal spray vaccine could stop bird flu at the door — blocking infection, reducing spread, and helping head off the next pandemic. Since first appearing in the United States in 2014, H5N1 [...]
These two viruses may become the next public health threats, scientists say
Two emerging pathogens with animal origins—influenza D virus and canine coronavirus—have so far been quietly flying under the radar, but researchers warn conditions are ripe for the viruses to spread more widely among humans. [...]
COVID-19 viral fragments shown to target and kill specific immune cells
COVID-19 viral fragments shown to target and kill specific immune cells in UCLA-led study Clues about extreme cases and omicron’s effects come from a cross-disciplinary international research team New research shows that after the [...]
Smaller Than a Grain of Salt: Engineers Create the World’s Tiniest Wireless Brain Implant
A salt-grain-sized neural implant can record and transmit brain activity wirelessly for extended periods. Researchers at Cornell University, working with collaborators, have created an extremely small neural implant that can sit on a grain of [...]
Scientists Develop a New Way To See Inside the Human Body Using 3D Color Imaging
A newly developed imaging method blends ultrasound and photoacoustics to capture both tissue structure and blood-vessel function in 3D. By blending two powerful imaging methods, researchers from Caltech and USC have developed a new way to [...]
Brain waves could help paralyzed patients move again
People with spinal cord injuries often lose the ability to move their arms or legs. In many cases, the nerves in the limbs remain healthy, and the brain continues to function normally. The loss of [...]
Scientists Discover a New “Cleanup Hub” Inside the Human Brain
A newly identified lymphatic drainage pathway along the middle meningeal artery reveals how the human brain clears waste. How does the brain clear away waste? This task is handled by the brain’s lymphatic drainage [...]
New Drug Slashes Dangerous Blood Fats by Nearly 40% in First Human Trial
Scientists have found a way to fine-tune a central fat-control pathway in the liver, reducing harmful blood triglycerides while preserving beneficial cholesterol functions. When we eat, the body turns surplus calories into molecules called [...]
A Simple Brain Scan May Help Restore Movement After Paralysis
A brain cap and smart algorithms may one day help paralyzed patients turn thought into movement—no surgery required. People with spinal cord injuries often experience partial or complete loss of movement in their arms [...]
Plant Discovery Could Transform How Medicines Are Made
Scientists have uncovered an unexpected way plants make powerful chemicals, revealing hidden biological connections that could transform how medicines are discovered and produced. Plants produce protective chemicals called alkaloids as part of their natural [...]
Scientists Develop IV Therapy That Repairs the Brain After Stroke
New nanomaterial passes the blood-brain barrier to reduce damaging inflammation after the most common form of stroke. When someone experiences a stroke, doctors must quickly restore blood flow to the brain to prevent death. [...]
Analyzing Darwin’s specimens without opening 200-year-old jars
Scientists have successfully analyzed Charles Darwin's original specimens from his HMS Beagle voyage (1831 to 1836) to the Galapagos Islands. Remarkably, the specimens have been analyzed without opening their 200-year-old preservation jars. Examining 46 [...]
Scientists discover natural ‘brake’ that could stop harmful inflammation
Researchers at University College London (UCL) have uncovered a key mechanism that helps the body switch off inflammation—a breakthrough that could lead to new treatments for chronic diseases affecting millions worldwide. Inflammation is the [...]
A Forgotten Molecule Could Revive Failing Antifungal Drugs and Save Millions of Lives
Scientists have uncovered a way to make existing antifungal drugs work again against deadly, drug-resistant fungi. Fungal infections claim millions of lives worldwide each year, and current medical treatments are failing to keep pace. [...]
