Theoretical Analysis of a Feedback Insensitive Semiconductor Ring Laser Using Weak Intracavity Isolation

External optical feedback can severely deteriorate the performance of semiconductor lasers. This paper proposes an integrated laser design that can withstand tens of percent of off-chip feedback, without requiring the integration of magneto-optic materials. The proposed laser consists of a ring cavity with a weak intracavity optical isolator. Sufficient gain difference between clockwise and counter-clockwise modes leads to unidirectional laser oscillation. Any reflected light is returned to a mode that is below threshold. This significantly reduces interactions between the feedback and the lasing mode. A rate-equation analysis is presented to show that the rin changes less than a factor 2 when less than -0.1 dB of the light is fed back into the laser and when intracavity isolation is 10 dB. Linewidth and optical output power change approximately 0.1% for these values.