The smallest optical gyroscope developed in the world

Scientists have developed the smallest optical gyroscope in the world – a device that helps vehicles, drones and portable electronics to know their orientation in 3D space. The new gyroscope, described in Nature Photonics, is 500 times smaller than the current best camera.

Originally, gyroscopes were sets of nested wheels, each rotating on a different axis, researchers at the California Institute said. In the United States, mobile phones are equipped with a microelectromechanical sensor, the modern equivalent, which measures the variations of forces acting on two identical mbades oscillating and moving in opposite directions.

Sagnac effect

The sensitivity of these MEMS gyroscopes being limited, optical gyroscopes have been developed to fulfill the same function but without moving parts and with a higher degree of precision, thanks to a phenomenon called the Sagnac effect, named after After the French physicist Georges Sagnac.

The smallest high performance optical gyroscopes available today are larger than a golf ball and are not suitable for many portable applications, the researchers explained. As optical gyroscopes are built smaller and smaller, the signal capturing the Sagnac effect is also, making it increasingly difficult to detect motion by the gyroscope, they said. Until now, this prevented the miniaturization of optical gyroscopes

The device developed by Caltech engineers led by Ali Hajimiri can detect phase shifts 30 times smaller than the best systems currently available. The new gyroscope improves performance by using a new technique called "improving reciprocal sensitivity". In this case, "reciprocal" means that it affects the two beams of light in the same way inside the gyroscope. Since the Sagnac effect relies on the detection of a difference between the two beams when they move in opposite directions, it is considered nonreciprocal. Inside the gyroscope, light travels through miniaturized optical waveguides (small light carrying ducts).

Optical path imperfections that may affect beams (such as heat fluctuations or light scattering), as well as any external interference affecting both beams. Professor Hajimiri's team has found a way to eliminate this mutual noise while leaving the signals of the Sagnac effect intact. The improvement of the reciprocal sensitivity thus improves the signal-to-noise ratio in the system and allows the integration of the optical gyroscope on a chip smaller than a grain of rice.