Backscattering Effect in Passive Resonant Laser Gyroscopes

Passive resonant laser gyroscopes (PRGs) have ultra-low shot noise limits and a great potential in Earth rotation detection. Backscattering causes lock-in effect as well as a Sagnac frequency shift in PRGs, and deteriorates the gyroscope's performance significantly, which lacks a theoretical analysis and verification in this type of instrument. In this paper, we develop a theoretical model for backscattering effect in PRGs, and validate the theoretical model using a PRG with a side length of 0.3 m. According to the proposed theoretical model, we are able to modify the lock-in region by changing the ratio of the light intensity of the two counter-propagating beams, which is a unique feature for PRGs. It is demonstrated that the lock-in region of this PRG can be reduced by 31%, which is consistent with the theoretical prediction. Furthermore, the Sagnac frequency shift introduced by backscattering in this PRG is also evaluated.