Babinet-Complementary Structures for Implementation of Pseudospin-Polarized Waveguides

Abstract: In this work, we prove a theorem that states the electromagnetic (EM) duality correspondence between eigenmodes of complementary structures, induces counterpropagating spin-polarized states in different types of waveguides where mirror reflection symmetries are preserved around one (or more) arbitrary plane(s). Similar to photonic topological insulators (PTIs), which support topologically non-trivial direction-dependent spin polarizations, our pseudospin-polarized systems support one-way states that manifest robustness, however, the advantage of our structures is that they can be implemented in extremely broad bandwidth simply using artificial dual impedance surfaces. Consequently, there is no need to bulk electromagnetic materials. On the basis of our theory, the concept of the pseudospin-polarized waveguide can be realized using Babinet complementary structures, ranging from microwave to THz regime. We design and develop various unidirectional waveguides and spin-filtered feature in the microwave regime is investigated.