Strongly confined waveguiding is one of the main applications of phononic crystals that can be achieved at any frequency and scale. Phononic crystal waveguides replace the cladding of classical homogeneous waveguides by a crystal possessing a complete phononic bandgap. We review the different material systems used to implement phononic crystal waveguides and how waveguiding is obtained by confining waves in a core or by coupling defects along a given direction. Finally, we introduce topological principles to design defect-less waveguides by exploiting the symmetry of crystals.

中文翻译：

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声子晶体波导的原理和特性

强约束波导是声子晶体的主要应用之一，可以在任何频率和尺度上实现。声子晶体波导用具有完整声子带隙的晶体代替了经典同质波导的包层。我们回顾了用于实现声子晶体波导的不同材料系统，以及如何通过将波限制在核心中或通过沿给定方向耦合缺陷来获得波导。最后，我们介绍了拓扑原理，通过利用晶体的对称性来设计无缺陷波导。