Low loss silicon microring resonator as comb filter

Scattering loss caused by roughness of waveguide sidewalls is a key problem for long circumference microring based applications, such as comb filters. This paper presents a Si microring resonator incorporated with the multimode waveguide and single-mode waveguide, which suppresses the unwanted resonance of high-order modes while allowing the fundamental mode resonance with low loss. Both numerical and experimental results proved that the proposed solution is capable to achieve ~88.5% scattering loss reduction which is promising for narrow channel spacing comb filters.