Chip-scale magnetometer uses light for high-precision magnetic sensing

(Press-News.org) WASHINGTON — Researchers have developed a precision magnetometer based on a special material that changes optical properties in response to a magnetic field. The device, which is integrated onto a chip, could benefit space missions, navigation and biomedical applications.

High-precision magnetometers are used to measure the strength and direction of magnetic fields for various applications. However, many of today’s magnetometers must operate at extremely low temperatures — close to 0 kelvin — or require relatively large and heavy apparatus, which significantly restricts their practicality.

“Our device operates at room temperature and can be fully integrated onto a chip,” said Paolo Pintus from the University of California, Santa Barbara (UCSB) and the University of Cagliari, Italy, co-principal investigator for the study. “The light weight and low power consumption of this magnetometer make it ideal for use on small satellites, where it could enable studies of the magnetic areas around planets or aid in characterizing foreign metallic objects in space.”

In Optica, Optica Publishing Group's journal for high-impact research, the research team, led by Galan Moody of UCSB, with Caroline A. Ross of MIT also serving as a co-principal investigator, describe their new magnetometer. They show that the device can achieve a sensitivity comparable to that of other high-performance, but less practical, magnetometers.

“The magnetometer could be useful for magnetic navigation, providing an alternative navigation source in environments where GPS is jammed, spoofed or unavailable such as underwater, in tunnels or during electronic warfare,” said Pintus. “It could also benefit medical imaging methods such as magnetocardiography and magnetoencephalography, which currently depend on highly sensitive magnetometers that require bulky, costly equipment.”

Turning light into magnetic insight

The new magnetometer was developed as part of the U.S. National Science Foundation’s Quantum Sensing Challenges for Transformational Advances in Quantum Systems program. It builds on previous works in which the researchers used magneto-optic materials to develop a magneto-optic modulator and integrated magneto-optic memories for photonic in-memory computing.

For the new device, the researchers used a magneto-optical material called cerium-doped yttrium iron garnet (Ce:YIG), which was provided by Yuya Shoji from the Institute of Science, Tokyo. When an external magnetic field is present, light propagating through Ce:YIG experiences a phase shift that can be detected with an optical interferometer.

Optical interferometers work by splitting light into two paths and then recombining those paths. By placing the magneto-optic material in one of the paths, the researchers were able to measure whether the light in that path becomes brighter or dimmer, which was then used to determine the strength of the magnetic field.

To make the magnetometer practical, the researchers built it on silicon photonics, a technology that creates tiny optical devices using the same silicon found in microchips. This allowed them to create a device with minimal size, weight and power consumption that can be integrated with other chip-based optical components such as lasers and photodetectors.

“Historically, magneto-optic materials have been used almost exclusively in optical isolators and circulators, a specialized class of devices that enforce unidirectional light propagation,” said Pintus. “By incorporating magneto-optic materials directly onto a photonic integrated circuit, we expand the range of integrated photonic components and introduce functionalities that stem from their unique properties.”

The magnetometer operates with ordinary laser light, but the authors have shown that injecting quantum light can improve its performance. “The idea is similar to what’s already done in large optical interferometers used to detect gravitational waves, like LIGO,” explained Pintus. “By using squeezed light — a special quantum state of light — we can reduce noise and increase the instrument’s sensitivity.”

High sensitivity from a small device

Using a combination of multi-physics simulations and experimental measurements, the researchers showed that the device can detect magnetic fields ranging from a few tens of picotesla to 4 millitesla. For comparison, Earth’s magnetic field is about 100,000 times stronger than the minimum detectable field, yet around 1,000 times weaker than the maximum field the instrument can measure. This sensitivity matches that of high-performance cryogenic magnetometers, without their restrictive temperature, size, weight or power constraints.

“This research effort brought together specialists in modeling and fabrication of integrated optical devices, material science and quantum-level modeling of light–matter interactions,” said Pintus. “The synergy among these disciplines enabled us to demonstrate a high-performance device with capabilities that would not be attainable through any single field alone.”

Now that the researchers have taken an important step toward demonstrating the feasibility of their approach, they are working to improve performance by exploring alternative magneto-optic materials and integrating quantum elements for even greater sensitivity. They note that transitioning the research into a commercial product would require the challenging task of creating a fully integrated chip-based system that includes other key components, such as an integrated laser and photodetector.

Paper: P. Pintus, H. Wang, S. Srinivasan, S. Pinna, D. Huang, Y. Shoji, C. A. Ross, J. E. Bowers, G. Moody, “Integrated magneto-optic based magnetometer: classical and quantum limits” 12, (2025).

DOI: 10.1364/OPTICA.577791.

About Optica Publishing Group

Optica Publishing Group is a division of the society, Optica, Advancing Optics and Photonics Worldwide. It publishes the largest collection of peer-reviewed and most-cited content in optics and photonics, including 19 prestigious journals, the society’s flagship member magazine, and papers and videos from over 1200 conferences. With over 505,000 journal articles, conference papers and videos to search, discover and access, its publications portfolio represents the full range of research in the field from around the globe.

About Optica

Optica is an open-access journal dedicated to the rapid dissemination of high-impact peer-reviewed research across the entire spectrum of optics and photonics. Published monthly by Optica Publishing Group, the Journal provides a forum for pioneering research to be swiftly accessed by the international community, whether that research is theoretical or experimental, fundamental or applied. Optica maintains a distinguished editorial board of more than 60 associate editors from around the world and is overseen by Editor-in-Chief Prem Kumar, Northwestern University, USA. For more information, visit Optica.

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