Coupling of topological interface states in 1D photonic crystal

Coupling of topological interface states in a one dimensional photonic crystal has been systematically investigated in a broad energy region of electromagnetic spectrum. The robust topological interface states appear when the Zak phase between the adjoining photonic crystals are different at their common photonic bandgap. The coupled interface states created combining three photonic crystals are useful for the spatial confinement and enhancement of electric fields, which could find potential applications in nonlinear photonics and multichannel filters. Anticrossing observed in the dispersion confirms the strong coupling between the topological interface states and causes Rabi-like splitting between them. The splitting energy is found decreasing with increasing number of unit cells in the photonic crystal. The angular and polarization dependency of the coupled states are studied in detail. The resonant wavelength position and bandwidth of the dual reflectivity dips corresponding to the coupled interface states are polarization sensitive and tunable with varying angle of incidence of light.