Passive resonant laser gyroscope with improvement of the suppression of residual amplitude modulation eﬀects through correlation analysis


 Passive resonant gyroscopes (PRG) utilizing the Pound-Drever-Hall (PDH) method are expected to have a lower shot-noise limit in rotational rate measurement. However, there are also many technical obstacles in the way to touch the intrinsic noise ﬂoor. In this article, we ﬁnd that the residual amplitude modulation (RAM) eﬀect accrued in the phase locking process deteriorates the accuracy and stability of the output signal of PRGs, and becomes a dominant limiting factor, especially in the low-frequency range. Since the suppression is not good enough in the PRGs due to the strict requirements, we propose to use the Pearson correlation coeﬃcient (PCC) to evaluate the correlation between the RAM signal and the PDH signal to achieve a suﬃcient correlation before active servo control. With the implementation of this improvement, the RAM-induced relative frequency stability for the 12-m optical ring cavity is reduced down to 1.2 × 10^-18. The contribution of the RAM eﬀect to the rotational sensitivity of our 3 m × 3 m PRG is lowered to 8.0 × 10^-9 rad/s/√Hz at 1 mHz, which is one order of magnitude better than the unconstrained situation. With this upgrade, a rotational resolution of 5.2 × 10^-10 rad/s of the PRG is achieved, which is the best performance among all PRGs so far.