The plasma sheath causes the spacecraft’s communication signal to attenuate dramatically during the re-entry period, which seriously threatens the astronauts. However, valid experimental protocols have not been obtained hitherto. To realize the propagation of electromagnetic waves in negative permittivity background of the plasma sheath, alumina columns are embedded in the plasma background to form plasma photonic crystals, which can support the coupling of evanescent waves between the alumina columns. We experimentally demonstrate the realization of communication in blackout scenario by achieving a complete passing band in the plasma cutoff region. For high frequency communications in the plasma sheath, electromagnetic wave propagation based on topological edge states is also experimentally demonstrated. Furthermore, we realize a triply-degenerate Dirac cone formed dynamically at the center of the Brillouin zone by modulating the electron density, where electromagnetic wave exhibits high transmittance and does not experience phase accumulation at the Dirac point. Our work thus not only provides an effective approach to overcome the communication blackout problem, but the design can also be served as a promising experimental platform to explore topological electromagnetic phenomena.

中文翻译：

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等离子鞘层中停电通信、拓扑波导和狄拉克零折射率特性的实验观察

等离子鞘层导致航天器通信信号在重返大气层期间急剧衰减，严重威胁航天员安全。然而，迄今为止尚未获得有效的实验方案。为实现电磁波在等离子体鞘层负介电常数背景下的传播，在等离子体背景中嵌入氧化铝柱形成等离子体光子晶体，支持氧化铝柱间倏逝波的耦合。我们通过在等离子截止区域实现完整的通带，通过实验证明了在停电情况下通信的实现。对于等离子体鞘层中的高频通信，还通过实验证明了基于拓扑边缘状态的电磁波传播。此外，我们通过调制电子密度实现了在布里渊区中心动态形成的三次退化狄拉克锥，其中电磁波具有高透射率并且不会在狄拉克点处经历相位积累。因此，我们的工作不仅提供了一种克服通信中断问题的有效方法，而且该设计还可以作为探索拓扑电磁现象的有前途的实验平台。