Angular rate sensing based on mode splitting in an optical microresonator

Backscattering has been treated as one of the major error sources in resonant optic gyroscopes (ROG) in a traditional way, which has to be restrained. A microresonator with ultra-high quality factor can greatly enhance the backscattering light. As a result, it cannot be deemed as a disturbance noise anymore. Coupling of the scattering light and the original propagating light can induce mode splitting. The frequencies of the split modes change along with the angular rotation rate of the microresonator. Considering the Sagnac effect, the model that describes mode splitting in an active optical microresonator was modified and the explicit expression of angular rotation rate versus the splitting amount was derived. The resonator is preferred to work in the under-coupling regime by monitoring the reflection spectra at several excitation levels and taper fiber coupling conditions. Optical gain of the active medium can be utilized to manipulate the splitting profiles and to narrow the line widths, which helps the rate measurement. Theoretical analysis and simulation results show that the resolving power can reach 10^-6 (°)/s in a microresonator with a quality factor of 10⁸, providing a promising angular rate sensing mechanism.