Motion sensing just got smaller

Inertial navigation systems are widely used to determine the position of ships, aircraft, spacecraft, and other vehicles without relying on external references. Instead, they use internal sensors, such as accelerometers and gyroscopes, to continuously track their movement. Because even small measurement errors can accumulate over time, improving the accuracy and long-term stability of accelerometers is critical for achieving more precise and reliable inertial navigation.

Optomechanical sensors are a promising accelerometer technology, offering exceptional sensitivity and highly accurate measurements. However, achieving the long-term stability required for inertial navigation remains challenging, as their measurements can be affected by sources of drift. Ge et al. developed a different optomechanical accelerometer architecture designed to reduce sensitivity to these effects while maintaining high acceleration sensitivity.

“Many previous optomechanical accelerometers rely on optical resonances to detect the extremely small displacement of a mechanical proof mass,” said author Matt Eichenfield. “While resonant optical readout can provide very high sensitivity, the optical resonance itself is also sensitive to temperature fluctuations, laser wavelength drift, and other environmental perturbations. These effects can appear as apparent acceleration signals and degrade long-term stability.”

Instead of relying on optical resonance, the authors developed their accelerometer using a non-resonant, differential interferometric readout. Their device contains an on-chip Mach-Zehnder interferometer, which produces an optical phase shift in response to acceleration. Environmental disturbances, however, affect both arms of the interferometer equally, producing no change. This approach allows the device to maintain high sensitivity while improving its long-term stability.

Beyond inertial sensing, the same differential optomechanical approach could potentially be extended to other precision sensors, including force sensors and magnetometers.

“A particularly exciting next step is to extend this sensing architecture to an optomechanical vibratory Coriolis gyroscope,” said author Chang Ge. “By integrating piezoelectric actuators to drive the proof mass orthogonal to the sensing direction, the differential optical readout could be used to measure rotation rate with the goal of achieving low bias instability and ultimately enabling chip-scale inertial sensing for GPS-free navigation.”

Source: “Towards navigation-grade optomechanical accelerometers on a chip,” by Chang Ge, Daniel Dominguez, Allison Rubenok, Michael Miller, and Matt Eichenfield, APL Photonics (2026). The article can be accessed at https://doi.org/10.1063/5.0333148 .