Phase transition of non-Hermitian topological edge states in microwave regime

Recent advances in non-Hermitian topological phases have exploited the unusual features in photonics systems. In particular, the coupling effect and parity-time (PT) symmetry have been found to jointly determine the transition of topological edge states, which have yet to be detected directly in coupled PT-symmetric waveguides. In this work, we use a finite waveguide array described by the Su-Schrieffer-Heeger model to explicitly reveal the relation between the topological states and PT symmetry and unveil the condition for the coexistence of topological edge states and PT phases. Microwave-near-field experiments have revealed non-trivial edge states in both exact- and broken-PT phases in ultrathin corrugated metallic coupled waveguide arrays. This work thus establishes an integrated microwave waveguide platform based on which more interesting physics and functional devices related to topological photonics and PT symmetry may be developed. Published under license by AIP Publishing.