Regulation of Non-Hermiticity in Spiral Microring Add-Drop Filters

For on-chip optical cavities, various approaches have been investigated for steering the non-Hermiticity for realizing novel phenomena, such as exceptional points or PT-symmetry breaking. However, Here we report spiral microrings as an integrable deformed microcavity designed on silicon nitride-on-silica platform. By fine-adjusting the spacing between two spiral notches, the backscattering strength between clockwise and counterclockwise components can be controlled, which has been revealed in both simulation and experimental results.