Abstract

Silicon microrings have proven their value in numerous optical applications. Usually it’s desirable for them to have a high Q factor, thus a very narrow linewidth. But this will frequently facilitate resonance splitting because sidewall roughness induces backscattering and this couples the clockwise (CW) and counter-clockwise (CCW) propagating modes in the ring waveguide [1]. As a consequence their degeneracy will be broken. Resonance splitting is problematic in almost all of the microring based applications. Even if the splitting can be avoided by broadening the resonance linewidth, the backreflection to the in port and unwanted transmission to the add port are still inevitable. These two effects can cause unwanted interferences in larger circuits or cause laser instabilities.

© 2017 IEEE