New High Precision Chip-Based Laser Gyroscope Can Measure Earth’s Rotation
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New High Precision Chip-Based Laser Gyroscope Can Measure Earth's Rotation:
Optical gyroscopes are used in applications such as aircraft navigation systems, while MEMS gyroscopes are found in devices like smartphones. For the last few decades, researchers have wondered whether it would be possible to bridge the gap between these two technologies and create a new type of gyroscope that combines the precision of laser gyroscopes with the ease of manufacture of MEMS gyroscopes. Now, Caltech scientists have developed an optical gyroscope that marries some of the best characteristics of each into one device.
In a new paper published in Nature Photonics, Kerry Vahala (BS '80, MS '81, PhD '85), Caltech's Ted and Ginger Jenkins Professor of Information Science and Technology and Applied Physics, describes a laser gyroscope his lab built from a piece of silicon-based material in much the same way that MEMS devices are manufactured. The new type of gyroscope has achieved something considered a benchmark for gyroscopes: the ability to measure the rotation of the earth.
All optical gyroscopes, including the one developed by Vahala, make use of something known as the Sagnac effect to measure rotation. Two light waves traveling in opposite directions around a ring-like path will have equal propagation times. However, when the path rotates, the time to reach a specific point on the rotating path will be different for each wave. This difference provides a measure of the rate of rotation and can be determined very precisely by measuring the interference between the two light waves.
[...] In Vahala's gyroscope, the pathway is a circular silica disk, and the laser light is generated by high frequency vibrations in the disk through a process called stimulated Brillouin scattering.
Although the shorter light path in Vahala's gyroscope helps to keep the device smaller, it could also result in lower sensitivity. To make up for that, the light is "recycled," says Yu-Hung Lai, co-author on the paper. "The light is allowed to circulate around the path again and again, creating a stronger Sagnac effect and greater sensitivity to rotation."
Journal Reference:
Yu-Hung Lai, Myoung-Gyun Suh, Yu-Kun Lu, et al. Earth rotation measured by a chip-scale ring laser gyroscope, Nature Photonics (DOI: 10.1038/s41566-020-0588-y)
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