Zero GVD slow-light originating from a strong coupling of one-way modes in double-channel magneto-optical photonic crystal waveguides

We have studied the coupling effect of topological photonic states in a double-channel magneto-optical photonic crystal waveguide by introducing a two-stranded ordinary Al2O3 photonic crystal as the coupling layer. There exist both M1 (odd) and M2 (even) one-way modes simultaneously in the bandgap. Interestingly, M1 mode is always a fast-light mode with large group velocity (v(g)) and large group velocity dispersion (GVD) regardless what the radius (R-A) of Al2O3 rods is. However, when R-A is appropriate, M-2 mode becomes a very slow-light mode exhibiting near-zero v(g) and zero GVD simultaneously. The physical reason of such slow-light is attributed to the strong coupling effect between the one-way edge modes in both sub-waveguides. Furthermore, the simulation results show that the robustness of both the fast- and slow-light modes are extremely strong against perfect electric conductor defect and the one-way transmittance is close to 100%. Besides, the PEC defect can cause significant phase delay. These results hold promise for many fields such as signal processing, optical modulation, and the design of various topological devices. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

The coupling effect of topological photonic states in a double-channel magneto-optical photonic crystal waveguide was studied, revealing both fast and slow light modes with strong robustness against perfect electric conductor defects and close to 100% one-way transmittance.