Resonant optical gyro: Monolithic vs. hybrid integration

Since several decades, angular velocity sensors are considered crucial devices in a wide range of vehicles such as military and civil airplanes, military ships, submarines, satellites, space launchers, and long-range ballistic missiles. The interest towards miniaturized gyroscopes for aerospace and defense industry has given rise to an increasing research effort aiming at the scaling of optical gyros through integrated optical technologies. In particular, the resonant optical gyro (ROG) has been identified as the ideal candidate for a new generation photonic angular velocity sensor. Two technological approaches are available to implement the ROGs, i.e., the hybrid integration of optoelectronic components manufactured on different substrates or the monolithic integration of all components on a single chip. The two options are critically discussed and compared in this paper with a special attention on integrated gyroscopes (gyro-on-a-chip, GoC) in silica on silicon and indium phosphide that have been recently theoretically and experimentally studied, demonstrating promising results.