This Perspective examines the emerging applications of photonic topological insulators (PTIs) in the microwave domain. The introduction of topological protection of light has revolutionized the traditional perspective of wave propagation through the demonstration of backscatter-free waveguides in the presence of sharp bending and strong structural defects. The pseudospin degree of freedom of light enables the invention of unprecedented topological photonic devices with useful functionalities. Our aim is to present a brief introduction of recent developments in microwave PTI demonstrations. We give a clear comparison of different PTI realizations, summarize the key features giving rise to topological protection, and present a discussion of advantages and disadvantages of PTI technology compared to existing microwave device technology. We conclude with forward-looking perspectives of how the advantages of this technology can best be exploited.

中文翻译：

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光子拓扑绝缘体的微波应用

本视角考察了光子拓扑绝缘体 (PTI) 在微波领域的新兴应用。光的拓扑保护的引入通过在存在急剧弯曲和强烈结构缺陷的情况下展示无反向散射波导，彻底改变了波传播的传统观点。光的赝自旋自由度使发明具有有用功能的前所未有的拓扑光子器件成为可能。我们的目的是简要介绍微波 PTI 演示的最新发展。我们对不同的 PTI 实现进行了清晰的比较，总结了引起拓扑保护的关键特性，并讨论了 PTI 技术与现有微波器件技术相比的优缺点。