Gyroscopes are devices that help vehicles, drones and portable and handheld electronic devices know their orientation in three-dimensional space. They…
Gyroscopes are devices that help vehicles, drones and portable and handheld electronic devices know their orientation in three-dimensional space. They are common in almost all technologies that we trust every day. Originally, gyroscopes were sets of nested wheels, each spinning on another shoulder. But open a cell phone today, and you’ll find a microelectromechanical sensor (MEMS), today’s equivalent, which measures changes in forces that act on two identical masses that oscillate and move in opposite directions. These MEMS gyroscopes are limited in their sensitivity, so optical gyroscopes have been developed to perform the same function but without moving parts and greater accuracy with a phenomenon called the Sagnac effect.
What is Sagnac Effect?
] The Sagnac effect, named after French physicist Georges Sagnac, is an optical phenomenon that is rooted in Einstein’s theory of general relativity. To create it, a beam of light is divided into two, and the twin beams travel in opposite directions along a circular path and then meet with the same light sensor. The light travels at constant speed, so that the unit is rotated ̵
1; and thus the way the light moves – causes one of the two beams to reach the detector before the other. With a loop on each orientation axis, this phase shift, known as the Sagnac effect, can be used to calculate orientation.
The smallest high performance optical gyroscopes available today are larger than a golf ball and are not suitable for many portable applications. Since optical gyroscopes are built less and less, the signal that captures the Sagnac effect makes it more difficult for the gyroscope to detect motion. So far, this has prevented miniaturization of optical gyroscopes.
Caltech engineer led by Ali Hajimiri, Bren Professor of Electrical Engineering and Medical Technology in the Technology and Applied Sciences Division, developed a new optical gyroscope that is 500 times less than the current state of the art device, but they can detect phase shift which is 30 times less than those systems. The new device is described in a paper published in November Photonics by November Photonics.
How It Works
The new gyroscope from Hajimir’s lab achieves this improved performance by using a new technology called “Mutual Sensitivity Enhancement.” In this case, “mutual” means that it affects both rays in the light inside the gyroscope in the same way. Because the Sagnac effect is dependent on the discovery of a difference between the two rays as they travel in opposite directions, it is considered non-erroneous. Inside the gyroscope, the light flows through miniaturized optical waveguides (small wires carrying light, performing the same function as the cables make for electricity). Errors in the optical path that may affect the rays (such as thermal fluctuations or light scattering) and possible external disturbances affect both the rays in the same way.
Hajimir’s team found a way to wipe out this mutual noise while leaving the signals from Sagnac power intact. Mutual sensitivity enhancement thus improves signal-to-noise ratio in the system and enables integration of the optical gyro on a chip that is less than one risk tower.
The paper is called “Nanophotonic Optical Gyroscope with Mutual Sensitivity Enhancement.” Graduate student Parham Khial is leading author, and doctoral student Alexander White is co-authors. This research was funded by the Rothenberg Innovation Initiative.
Material provided by California Institute of Technology . Original written by Robert Perkins. Note! Content can be edited for style and length.