New York, February 2, 2026 — The invention of tiny devices capable of precisely controlling the direction and behavior of light is essential to the development of advance technologies. Researchers at the Advanced Science Research Center at the CUNY Graduate Center (CUNY ASRC) have taken a significant step forward with the developed of a metasurface that can turn invisible infrared light into visible light and aim it in different directions—without any moving parts. The details of their work are explained in a new paper published in the journal eLight .
The novel metasurface is constructed of an ultra-thin chip patterned with tiny structures smaller than the wavelength of light. When hit with an infrared laser, the chip converts the incoming light to a higher color (or frequency) and sends the new light out as a narrow beam that can be steered simply by changing how the incoming light is polarized.
In their experiments, the team converted infrared light around 1530 nanometers—similar to the light used in fiber-optic communications—into visible green light near 510 nanometers and steered it to chosen angles.
"Think of it as a flat, microscopic spotlight that not only changes the color of light but also points the beam wherever you want, all on a single chip," said Andrea Alù, founding director of the CUNY ASRC Photonics Initiative and Distinguished Professor at the CUNY Graduate Center. "By making different parts of the surface work together, we get both very efficient conversion of light and precise control over where that light goes."
Addressing a long-standing tradeoff
Engineers have long used metasurfaces—flat, nanostructured materials—to bend and shape light. However, these devices usually face a tradeoff:
- Structures that control light at each pixel of the surface are flexible but not very efficient at boosting light.
- Structures that allow light waves to spread and interact across the whole surface can be very efficient, but they lose fine control over the beam shape.
The new CUNY device is the first to do both at once for nonlinear light generation, in which one color of light is converted into another. It uses a special kind of collective resonance—called a quasi–bound state in the continuum—to trap and amplify the incoming infrared light across the entire surface. At the same time, each tiny building block on the surface is rotated in a carefully designed pattern, giving the outgoing light a position-dependent phase, like a built-in lens or prism.
Because of this design, the chip produces third-harmonic light—light whose frequency is three times that of the incoming beam—while steering the new beam into specific directions. The direction flips when the polarization of the incoming light is flipped, offering a simple "knob" to control beam steering.
The result is a third-harmonic signal that is about 100 times more efficient than in comparable devices that can shape beams but lack these collective resonances.
Toward tiny light sources and on-chip beam steering
The ability to efficiently generate and steer new colors of light on a flat chip has wide-ranging potential uses.
"This platform opens a path to ultra-compact light sources and beam-steering elements for technologies like LiDAR, quantum light generation, and optical signal processing, all integrated directly on a chip," said lead author Michele Cotrufo, a former postdoctoral fellow at CUNY and now an assistant professor at the University of Rochester. "Because the concept is driven by geometry, not by one specific material, it can be applied to many other nonlinear materials and across different colors of light, including the ultraviolet."
Future designs could stack or combine several metasurfaces, each tuned slightly differently, to operate efficiently over a broader range of wavelengths, the researchers say.
This work was supported by the U.S. Department of Defense, the Simons Foundation, and the European Research Council.
DOI: 10.1186/s43593-025-00116-7
About the Advanced Science Research Center at the CUNY Graduate Center
The Advanced Science Research Center at the CUNY Graduate Center (CUNY ASRC) is a world-leading center of scientific excellence that elevates STEM inquiry and education at CUNY and beyond. The CUNY ASRC's research initiatives span five distinctive, but broadly interconnected disciplines: nanoscience, photonics, neuroscience, structural biology, and environmental sciences. The center promotes a collaborative, interdisciplinary research culture where renowned and emerging scientists advance their discoveries using state-of-the-art equipment and cutting-edge core facilities.
About the Graduate Center of The City University of New York
The CUNY Graduate Center is a leader in public graduate education devoted to enhancing the public good through pioneering research, serious learning, and reasoned debate. The Graduate Center offers ambitious students over 50 doctoral, master's, and certificate programs of the highest caliber, taught by top faculty from throughout CUNY — the nation's largest urban public university. Through its nearly 40 centers, institutes, initiatives, and the Advanced Science Research Center, the Graduate Center influences public policy and discourse and shapes innovation. The Graduate Center's extensive public programs make it a home for culture and conversation.
