Lock-in range in a semiconductor ring laser gyroscope

A locking range in a semiconductor ring laser (SRL) is theoretically analyzed. The simplified model accounting for the specific features of a SRL uses the carrier diffusion and the linewidth enhancement factor. For stabilization of the steady-state bidirectional lasing, we introduce in this model an active feedback loop that creates the intracavity losses proportional to the intensity difference between the counterpropagating waves. Frequency locking of the counterpropagating waves in the region of stability of steady-state bidirectional lasing is considered. Specific features inherent in the locking range in a SRL are discussed. When backscattering coupling is strong, the frequency locking of the counterpropagating waves does not switch to a beat regime at any rotation rate. In the case of weak backscattering coupling, analytical expressions for the locking range are derived. It is shown that an active feedback loop has a strong impact on a locking range. In a He-Ne laser, the locking range is determined by dissipative backscattering, and there is no locking with conservative scattering. Unlike a He-Ne laser, conservative backscattering in a SRL has a strong impact on the locking range.