OPTICAL GYROSCOPES: External-cavity semiconductor ring-laser gyro achieves single-mode operation

摘要

A team of scientists is the first to develop an external-cavity semiconductor ring-laser gyroscope that achieves single-mode operation. Previous designs based on coupling a semiconductor optical amplifier (SOA) to an external laser cavity achieved only low-performance multimode operation. The team includes scientists at Thales Research and Technology (Palaiseau, France), the Centre National de la Recherche Scientifique (CNRS) UPR 20 Laboratoire de Photonique et Nanostructures (Marcoussis, France), and the CNRS and Montpellier University Institut d'Electronique du Sud (Montpellier, France). To achieve single-mode, high-performance rotation sensing, the researchers implemented a free-space cavity containing a quantum-well half-vertical-cavity semiconductor-emitting laser (1/2VCSEL) structure that acts as an active mirror. The "beat" signal that is proportional to the rotation rate of the gyroscope is obtained from the interference of two counterpropagating waves in the cavity (see figure). It turns out that coupling between the gain medium in a 1/2VCSEL and the external cavity is easier to achieve than in an SOA design because the pump area and the cavity mode are both circular and of a comparable diameter, creating a higher-finesse cavity due to reduced injection losses.