Spectral causality-induced optical isolation in a non-Hermitian-modulated photonic cavity

An optical isolator is reported using a coupled cavity photonic molecule. It is shown that by non-Hermitian modulation of the coupling between the cavities, spectral causal and anti-causal response from the cavity can be obtained allowing the flexibility to regulate power between different Floquet modes. The distribution of optical energy between the Floquet modes is exploited to realize an optical isolator by cascading two modulators with a passive filter in between. A complete and general analytical model is developed for the non-Hermitian modulation, and the cavity parameters are optimized to ensure efficient operation. The reported results underscore the potential of dynamic photonic molecules and open new possibilities for simultaneous concurrent phase and loss dynamics in such systems.