Edge States and Topological Transitions in 1D Metal–Dielectric Photonic Crystals

Metal–dielectric photonic crystals (MDPCs) composed of alternating metallic and dielectric layers provide a versatile platform for exploring band hybridization, gap formation, and defect states in coupled optical cavities. By introducing controlled perturbations to mirror thickness in 1D MDPC, we observe the splitting of evenly spaced resonances into sub-bands and the opening of a Peierls-type gap. As the perturbation increases, mid-band states progressively collapse into the gap and localize at the system boundaries, revealing the emergence of edge states. This behavior reflects the physics of dimerized coupling models such as the Su–Schrieffer–Heeger (SSH) chain, demonstrating the presence of edge states and strongly suggesting their topological origin. Our results show that nanoscale structural tuning enables control of photonic band topology and the realization of topological edge states in one-dimensional plasmonic–organic lattices.