Investigating the Spectral Response of a Taiji-CROW Device

We report a study on modeling, designing, and testing an integrated photonic structure based on a sequence of two taiji microresonators coupled with a middle link microresonator. The so called taiji-CROW device exhibits strong unidirectional reflection by design and a non-reciprocal intermodal coupling due to its non-Hermitian nature. Our study provides design constraints to preserve the ideal operation of the structure by quantifying a minimum ratio between the coupling coefficients and the backscattering coefficients. This ratio is valuable to avoid surface roughness problems in designing topological integrated photonic devices based on arrays of microresonators.