Amplification of optical activity in a fiber loop resonator

In this paper, we have theoretically studied an effective amplification of optical activity by a fiber loop resonator. We propose a scheme in which an optically active element is placed in the loop segment of the resonator. Assuming that the coupling in the resonator is polarization-independent, we have shown that initially small polarization plane rotation, which arises due to the optically active element, can be significantly amplified by tuning the resonator's closed-path phase. We have also studied the influence of losses on the amplification of optical activity. We have shown that the maximal amplification takes place under the condition of critical coupling, at which the attenuation parameter is equal to the resonator's effective reflection coefficient. We have also studied effective dichroism in such a system and shown the relevance of a critical coupling regime to that effect.