Terminal-Matched Topological Photonic Substrate-Integrated Waveguides and Antennas for Microwave Systems

In engineered photonic lattices, topological photonic (TP) modes present a promising avenue for designing waveguides with suppressed backscattering. However, the integration of the TP modes in electromagnetic systems has faced longstanding challenges. The primary obstacle is the insufficient development of high-efficiency coupling technologies between the TP modes and the conventional transmission modes. This dilemma leads to significant scattering at waveguide terminals when attempting to connect the TP waveguides with other waveguides. In this study, a topological photonic substrate-integrated waveguide (TPSIW) is proposed that can seamlessly integrate into traditional microstrip line systems. It successfully addresses the matching problem and demonstrates efficient coupling of both even and odd TP modes with the quasi-transverse electromagnetic modes of microstrip lines, resulting in minimal energy losses. In addition, topological leaky states are introduced through designed slots on the TPSIW top surface. These slots enable the creation of TP leaky-wave antennas with beam steering capabilities. A wireless link based on TPSIWs are further established that enables the transmission of distinct signals toward different directions. This work is an important step toward the integration of TP modes in microwave systems, unlocking the possibilities for the development of high-performance wireless devices.