High-efficiency topological waveguides in substrate-integrated valley photonic crystals

Recently, the study of waveguides in substrate-integrated planar platforms has attracted much attention due to its significance for microwave and millimeter-wave technologies. Here, we propose substrate-integrated topological photonic crystals (PhCs) that support robust valley edge states. However, such systems need to be interfaced with classical waveguide or transmission line techniques to bring this advanced field of physics to practical applications. A substrate-integrated topological waveguide with high-efficiency transmission is designed and presented in this paper, in which high-efficiency conversion from conventional transmission line waves to topologically nontrivial edge waves mimicking the quantum valley Hall effect is achieved by transition structure. In addition, we numerically verify the robustness of valley edge waves through random defects and Z-shaped interfaces at microwave frequencies. The proposed topological PhC waveguides have the characteristics of planar integration, easy fabrication, and efficient transmission, which pave the way for the manipulation of topological valley edge waves in an integrated platform.