Caltech chip steers light beams in 74 femtoseconds using metasurfaces
Researchers have created a metasurface-based system that uses the optical Kerr effect to redirect light beams at unprecedented speeds. This development offers a new approach for managing data in fields such as telecommunications and high-speed computing.
Researchers at the California Institute of Technology have developed an optical device capable of redirecting light beams at extreme speeds, an advance that addresses a longstanding bottleneck in photonic technology. The new system achieves beam steering in 74 femtoseconds, or 74 quadrillionths of a second. This duration is approximately equivalent to the time required for a light pulse to cross the width of a single human hair.
The achievement, described in a study published on June 22, 2026, in the journal Nature Nanotechnology, offers a new method for managing data and signals in fields ranging from telecommunications to high-speed computing. The team behind the research includes lead author Claudio Hail, now of UC Berkeley, along with Harry Atwater and Lior Michaeli.
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Overcoming Electronic Bottlenecks
Traditional optical modulation typically relies on electrical signals to alter the properties of a material. In these conventional systems, electrons are pushed to higher energy states before eventually relaxing back to their baseline. This process is constrained by the time needed for the electrons to dissipate that excess energy, usually limiting switching speeds to nanoseconds or picoseconds. According to Sciencesprings, the Caltech group bypassed these electronic constraints by avoiding electrical signals entirely.
Instead, the researchers utilized a two-beam system. A powerful "pump" beam, featuring a specific optical pattern, modifies the refractive index of a target material through a phenomenon known as the optical Kerr effect
. This effect shifts the motion of electrons within their atomic orbitals without exciting them into long-lived energy states. As a result, the modification to the material occurs almost instantaneously. A second, weaker "probe" beam then passes through the material and is deflected based on the pattern established by the pump.
Enhancing the Kerr Effect
While the optical Kerr effect provides the necessary speed, it is traditionally too weak to be practical for beam steering on its own. To amplify the process, the team engineered a metasurface from amorphous silicon. This sheet consists of nanoscale pillars, each designed to be smaller than the wavelength of the pump light. These structures cause light to linger and recirculate within the material, magnifying the refractive index change and creating a signal robust enough to redirect the probe beam by up to 13 degrees.
According to the research team, the current speed of 74 femtoseconds is limited primarily by the duration of the pump laser pulses rather than the physical properties of the metamaterial itself. Further refinement may enable even faster modulation speeds, potentially aligning the technology with theoretical developments such as time crystals and synthetic time-varying optical media.
Comparative Approaches to Beam Steering
| Mechanism | Primary Limitation | Typical Speed |
|---|---|---|
| Electrical/Liquid-Crystal | Electron relaxation | Nanoseconds to Picoseconds |
| Optical Metasurface | Laser pulse duration | 74 Femtoseconds |
Broader Context in Photonics
The field of beam steering remains a competitive area of development. Other institutions have pursued different strategies to achieve dynamic control over light. For example, researchers at Sandia National Laboratories previously demonstrated the ability to steer incoherent light sources, such as LEDs, using metasurfaces integrated with quantum dots. While that work focused on low-power applications like augmented reality and remote sensing, it similarly aimed to prove that light could be manipulated at speeds faster than a trillionth of a second.
Elsewhere, projects such as the MITRE Quantum Moonshot have focused on scaling quantum computing by steering millions of light beams using arrays of microscopic mechanical cantilevers.
The work at Caltech was supported by the Air Force Office of Scientific Research, the Swiss National Science Foundation, the Fulbright Fellowship program, and the Breakthrough Foundation, with infrastructure support from the Kavli Nanoscience Institute.
