- The new optical gyroscope can detect rotation as slow as 37 degrees per hour.
- The device uses silicon nitride, compatible with standard CMOS fabrication processes.
- The gyroscope's sensitivity stems from the ring structure's ability to retain light.
- Researchers plan further testing outside the laboratory.
Researchers at the University of California, Santa Barbara, and the California Institute of Technology have developed a chip-scale optical gyroscope capable of detecting rotation as slow as 37 degrees per hour — nearly 2,000 times slower than earlier silicon nitride designs. The advance brings the sensor closer to Earth's rotation rate of 15 degrees per hour. Ultimately, it could help enable compact navigation systems for aircraft, vehicles, and spacecraft operating in environments where GPS signals are unavailable. Unlike conventional gyroscopes that rely on mechanical motion, the new device detects rotation by using light propagating in a ring-shaped optical path.
The researchers say the approach can deliver high-precision sensing in a smaller, more durable package.
Technical details of the gyroscope
The experimental gyroscope uses silicon nitride, a material compatible with standard CMOS chip fabrication processes. Its sensing circuit measures about 24 millimeters in diameter, while the packaged device is only a few centimeters wide. The researchers combined two previously developed technologies: a Brillouin laser gyroscope from Caltech and a low-noise chip-scale laser platform developed at UC Santa Barbara with support from the U.S. Air Force Research Laboratory. Inside the device, two semiconductor lasers send light in opposite directions around a ring circuit. The interaction between light and vibrations in the material produces two stable laser signals.
When the device rotates, the frequencies of these signals shift slightly relative to each other. Measuring this difference allows the gyroscope to determine the rotation rate.
Key factors in sensitivity
The ring structure's ability to retain light is critical to its sensitivity. Its quality factor — the efficiency with which the optical cavity stores light — exceeds 163 million, enabling the device to isolate a narrow 2-megahertz bandwidth from an optical signal of roughly 200 terahertz. Photons remain in the cavity for nearly 100 nanoseconds, allowing light to circulate repeatedly. A larger ring also boosts sensitivity, because optical gyroscopes detect smaller rotations when light encloses a greater area. 'Our new gyroscope combines several advanced technologies to achieve high sensitivity in a format that can use standard CMOS chip-processing methods, and with only milliwatts of optical power,' said research team lead Daniel J. Blumenthal.
To evaluate the device, the researchers mounted the packaged chip on a piezoelectric rotation stage that moved back and forth at controlled frequencies. A separate optical interferometer measured the stage's actual motion, providing a reference for comparison with the gyroscope's readings. The sensor produced a linear response and detected rotation as slow as 37 degrees per hour. Compared with the 72,000 degrees per hour measured by the researchers' earlier silicon nitride Brillouin gyroscope, the result demonstrates the improvement, confirming that low-noise lasers and high-quality optical cavities can enhance rotation sensitivity on photonic chips.
However, the new device has not yet achieved direct measurement of Earth's rotation and remains a laboratory prototype rather than a fully integrated navigation sensor. The researchers are working to reduce unwanted light scattering, which could affect measurement stability. They also plan to conduct tests outside the lab before integrating the lasers, photodetectors, and other components into a compact system. The findings have been published in Optics Letters.
Application potential of the new gyroscope
The development of this miniature optical gyroscope marks a significant advance in navigation technology, particularly for environments where GPS cannot be relied upon. Its high sensitivity and miniaturized design make it suitable for a range of applications including aircraft, vehicles, and spacecraft. As the technology matures further, such gyroscopes have the potential to play a key role in autonomous driving, drones, and other high-precision navigation systems. The research team's efforts focus not only on improving performance but also on addressing challenges such as light scattering to ensure the stability and reliability of the final product.