Analysis of Lock-In Threshold Variation in Laser Gyroscopes Operating at Resonance Frequency

The lock-in effect is the main source of error in laser gyroscopes, primarily originating from backscattering caused by the mirrors in the gyroscope resonant cavity. In order to investigate how the lock-in threshold varies, this paper uses the vector sum method to deduce and demonstrate that by adjusting the phase of each scattering vector, it is possible to improve the locking range. By employing theories of backscattering scalar and mode-coupling along with the resonant cavity mirrors, this study discusses the lock-in threshold, backscattering coefficient amplitude, phase, and their relationship with the cavity structure when the laser gyroscope is operating at its resonance frequency. Experimental results show that changes in the cavity structure can lead to a 30-fold variation in the lock-in threshold, validating the correctness of the theoretical analysis.