Nonreciprocal Polarization Coupling via Magneto-Optic Effect in Silicon Micro-Ring Resonator

The whispering gallery modes (WGMs) are studied theoretically in a proposed magneto-optic (MO) silicon micro-ring resonator with a radial magnetic field. The dispersion relations between both the frequency and polarization of the resonant mode and the gyration coefficient are achieved through Finite-Element Method (FEM). Nonreciprocal polarization coupling is observed between the intrinsic quasi-TM and quasi-TE modes, due to their different frequency shift coefficients originating from the magneto-optic effect. This polarization coupling results in the rapid changes of linear polarization degrees of the supermodes. The nonreciprocal mode coupling is universal and will be of practical value for the MO optical integration.