Realization of dual-band topological states in Su-Schrieffer-Heeger-like photonic crystal slabs

We design the bilayer mirror-symmetric (I-shaped) photonic crystal slabs supporting dual-band topological edge states simultaneously, which is confirmed by the topological phases and localized field distributions. By adjusting the coupling strengths at different positions of the I-shaped structure, the band structures can display different topology in different frequency bands, and the dual-band or single-band edge states can emerge flexibly at two or one band gaps, thus enabling high performance in manipulating topological states. Moreover, we also investigate the influence of broken mirror-symmetry Mz on the dual-band states. The study provides a promising way to realize multiband topological states and improve the efficiency of robust light transport.