Influence of Feedback Level on Laser Polarization in Polarized Optical Feedback

The influence of feedback level (or the amplitude of feedback light) on laser polarization in polarized optical feedback is investigated. A polarizer is placed in the feedback cavity to form the polarized feedback, and an attenuator is placed in the feedback cavity to tune the feedback level. The laser intensity and polarization vary dramatically at different transmissivities of the attenuator. According to the experimental phenomenon, the range of the attenuator transmissivity is divided into three zones: the flipping zone, monostable zone, and bistable zone. In the monostable zone, the laser polarization is always perpendicular to the axis of the polarizer in the feedback cavity. This may provide an effective way to choose or control laser polarization. A theoretical model based on the self-consistency of laser oscillation is presented to analyze the experimental results.