A new exceptional point condition for coupled microresonators with coupled mode theory in space

We derive new exceptional point (EP) conditions of the coupled microring resonators using coupled mode theory in space, a more accurate approach than the commonly used coupled mode theory in time. Transmission spectra around EPs obtained from the two models have been compared on two material platforms, revealing non-negligible deviations. Our analysis provides a guide for accurately determining parameter sets of coupled microrings at EPs and deepens our understanding on parity-time-symmetric coupled resonators at EPs.