Nonlinear Polarization Rotation in Semiconductor Optical Amplifiers With Linear Polarization Maintenance

We propose a geometrical model based on the concept of dynamic eigenstates of polarization to describe the behavior of nonlinear polarization rotation (NPR) arising in semiconductor optical amplifiers (SOAs). The rotation axis with respect to either the bias current or the optical power variation is demonstrated on the PoincarÉ sphere (PS), meanwhile a procedure to find the rotation axis is presented. Thus, the SOA-based NPR with linear polarization maintenance (zero polarization ellipticity angle) can be achieved experimentally. The rotation of polarization azimuth on the PS with respect to the bias current, the probe signal power, and the pump signal power variation is measured experimentally. The 180$^{\circ}$ phase difference between the transverse electric and the transverse magnetic modes can be all achieved with linear polarization maintenance.