Reflection-free Transmission in Time-reversal Symmetry-proteced Slot Line Waveguide

摘要

A slot line waveguide that incorporates an enclosure in the form of a perfect-magnetic conductor (PMC) is presented. The configuration exclusively supports the propagation of a quasi-transverse electromagnetic (TEM) mode, that is shown to be immune to reflections associated with bends in the propagation pathway. This is due to the mode forming time-reversal symmetry-warranted pseudospin states (decoupled polarizations), which are locked to the wavevector. Generally, spin-polarized states like in photonic topological insulators (PTIs) can exhibit backscattering-immune transmission if the scatterer does not flip the spin. Unlike PTIs, however, the proposed structure does not demand a special global behavior of the wavefunction of a periodic system. Here, the pseudospin property is intrinsic to the quasi-TEM mode and is simply enforced by eliminating all other modes including plane waves through the use of the PMC cover. We show a proof-of-concept design that is compatible with low-cost printed-circuit-board fabrication process as well as numerical full-wave simulation results. The evident competitive performance and simplicity of the proposed waveguide make it attractive for numerous microwave, millimeter-wave and terahertz applications.