Design of polarization-insensitive SOI ring resonators using cladding stress-induced birefringence and MMI couplers

A novel silicon-on-insulator ring resonator design is described that uses a multi-mode interference coupler to achieve polarization independent coupling, and cladding stress induced birefringence control to eliminate the difference in round trip phase accumulation between the TE and TM polarized waveguide modes. The design parameters are determined for a polarization independent SOI ring resonator with 1.5 μm ridge height and width. The resonator has a 0.5 nm free spectral range and -30 dB transmission contrast ratio, and with very modest fabrication requirements.