Broadside Radiation From Chern Photonic Topological Insulators
Zhixia Xu, Meng Wang, Shaojun Fang, Hongmei Liu, Zhongbao Wang, Daniel F. Sievenpiper
Abstract
Broadside radiation from Chern photonic topological insulators (PTIs) is studied in this work. The one-way dispersion of the topological edge mode is located in the fast wave region, making leaky-wave radiation possible. In this communication, design guidelines are presented and validated by full-wave simulations: the Berry curvature and the Chern number of photonic crystals are calculated to design a topological edge mode, then a leaky-wave antenna is proposed where a perturbation is utilized around the source location to eliminate open-stopband behavior and generate broadside radiation with high efficiency. It is demonstrated that leakage of the topological edge mode is capable of both frequency and bias scanning to generate a steerable beam across the broadside direction. Moreover, the mechanism behind the immunity of PTIs to defects is also investigated in detail. Although topological edge waves can bypass PEC-slab defects ideally, the phase change along the defect affects the radiation pattern. The switch between sum-difference beams by tuning the scale of the PEC-slab is direct evidence to verify our analysis. To sum up, the open-stopband behavior is overcome to realize broadside radiation, and the conditional robustness of PTIs in terms of antennas is clarified.