The Giroskop Laser Measures Earth's Rotation With Extraordinary Precision

The Giroskop Laser Measures Earth's Rotation With Extraordinary Precision

The giroskop laser measures Earth's rotation with extraordinary precision.giroskop laser This will help scientists refine models of global mass transport phenomena and tease out subtle effects in Einstein's theory of relativity (SN: 7/17/20).

Unlike mechanical gyroscopes, optical ones use lasers to detect rotation.giroskop laser An optical gyroscope consists of an optical cavity that guides light around a square path, with two laser beams combining at the end of the pathway to create an interference pattern that’s proportional to the direction of rotation. This is known as the Sagnac effect. Optical gyroscopes are the highest-performance type, and are used in onboard inertial navigation systems in aircraft, submarines, ships, and spacecraft.

However, these sophisticated devices suffer from a flaw called “lock-in” at low rotation rates.giroskop laser As the ring-shaped path rotates, the frequency of the Sagnac interferometer's counter-propagating laser modes shifts by a few hundred kHz, causing one to increase and the other to decrease, which in turn alters the interference pattern.

Vahala’s group, whose coauthors include graduate students Boqiang Shen and Heming Wang, solved this problem by pumping their gyroscope’s counter-pumped stimulated Brillouin laser (CP-SBL) with two frequencies that are opposite each other. This nonreciprocal bias — generated by a thin Faraday rotator or longitudinal magnetic field in the resonator’s gain medium — separates the CP-SBL modes' circular polarizations and prevents them from locking into the same state.

The result is that the gyroscope's interference pattern remains stable, even as the ring's rotation rate gets lower and lower. This enables it to detect extremely small changes in the length of the Earth day, a critical quantity for teasing out subtle effects in Einstein's theory that a rotating planet drags spacetime along with it.

Tags:ring laser gyro