Researchers at NIST have developed a highly sensitive nanophotonic motion sensor that can be batch-fabricated on a silicon chip at low cost. The device combines a microelectromechanical system (MEMS) with a sensitive optical resonator that can be accessed using conventional optical fibers.
The sensor consists of a silicon microdisk optical cavity with a silicon nitride ring suspended a few hundred nanometers above it. Changes in the distance between the disk and ring are measured by changes in the strength of the interaction between the evanescent light at the disk’s surface and the ring.
The cavity’s high optical quality factor allows light to make several thousand round-trips before leaking out, accumulating information about the ring’s position with each round-trip. This enables precision displacement measurements close to the limit imposed by the quantum mechanical uncertainty principle.
The researchers have also developed a feedback system that reduces the Brownian motion of the actuator by a factor of 1000, increasing the mechanical force-sensing bandwidth by more than a factor of 2000. The overall device achieves a combination of speed and precision that is completely unreachable with conventional MEMS sensors.
The next step is to integrate these sensors and actuators into highly sensitive, stable and compact cantilever probes for atomic force microscopy.
Keywords: Metrology, Nanoscale, Precision, Sensing, Uncertainty
