Measuring the Earth's rotation using a chip-scale Brillouin laser gyroscope

Counter-propagating lightwaves within a closed rotating loop enable rotation measurement as a result of the Sagnac effect. And modern optical gyroscopes use long coiled optical fiber paths (fiber optic gyroscopes) or resonant recirculation (ring laser gyroscopes) to greatly enhance this effect. In recent years, the possibility of chip-based optical gyroscopes has garnered considerable attention. Such integrated optical gyrocopes could enjoy the advantages of integration and scalable manufacturing, and would offer rugged designs for operation in challenging environments. Compact or chip-based ring laser gyroscopes, passive resonant gyroscopes, and interferometric gyroscopes have been reported. Here we first review some of the enabling technologies of chip-integrated designs, overview recent results, and then focus on a chip-based laser gyroscope that has been used to measure the Earth's rotation. The sensitivity of the gyroscope is limited by fundamental noise sources that are discussed. Also, operation of the gyroscope near an exceptional point is possible and the features of this mode of operation are reviewed.