A dual-channel unidirectional filter of magneto-optical photonic heterostructure with a ring cavity

A dual-channel unidirectional filter of magneto-optical photonic crystal (MOPC) heterostructure with a ring cavity is proposed, based on topological edge states (TES). The ring cavity, which is composed of two MOPCs with opposite magnetic field, supports even and odd TESs. Finite element method (FEM) simulation results show that there are two perfect transmission peaks in drop port and dual-channel unidirectional filtering is achieved, which originates from cavity resonances of even and odd TESs. Furthermore, we investigate the influences of the cavity size, the magnetic field applied on MOPC, and the distance between the cavity and waveguide on dropping performance. A tunable dual-channel unidirectional filter with high Q factor up to 48000 can be achieved. Moreover, the proposed structure has strong robustness and can achieve immunity to various defects, including added PEC and the perturbation of the geometry parameter. Therefore, we obtain a waveguide-cavity structure based on MOPC heterostructure with the universality and efficient dropping performance, which provides the possibility for double-band one-way multiplexer and sensor.