Polarization conversion in ring resonator phase shifters.

The effect of the polarization rotation induced by curved waveguides on the spectral behavior of phase shifter ring resonators is investigated both theoretically and experimentally. At resonance the polarization rotation that takes place in curved waveguides is strongly enhanced. The effect can be detrimental, or it can be exploited for new devices. The ring vectorial transfer function is derived, together with the conditions for the total conversion of TE polarization into TM polarization. These conditions are verified experimentally.