Abstract Electron beams in electron microscopes are efficient probes of optical near-fields, thanks to spectroscopy tools like electron energy-loss spectroscopy and cathodoluminescence spectroscopy. Nowadays, we can acquire multitudes of information about nanophotonic systems by applying space-resolved diffraction and time-resolved spectroscopy techniques. In addition, moving electrons interacting with metallic materials and optical gratings appear as coherent sources of radiation. A swift electron traversing metallic nanostructures induces polarization density waves in the form of electronic collective excitations, i.e., the so-called plasmon polariton. Propagating plasmon polariton waves normally do not contribute to the radiation; nevertheless, they diffract from natural and engineered defects and cause radiation. Additionally, electrons can emit coherent light waves due to transition radiation, diffraction radiation, and Smith-Purcell radiation. Some of the mechanisms of radiation from electron beams have so far been employed for designing tunable radiation sources, particularly in those energy ranges not easily accessible by the state-of-the-art laser technology, such as the THz regime. Here, we review various approaches for the design of coherent electron-driven photon sources. In particular, we introduce the theory and nanofabrication techniques and discuss the possibilities for designing and realizing electron-driven photon sources for on-demand radiation beam shaping in an ultrabroadband spectral range to be able to realize ultrafast few-photon sources. We also discuss our recent attempts for generating structured light from precisely fabricated nanostructures. Our outlook for the realization of a correlative electron-photon microscope/spectroscope, which utilizes the above-mentioned radiation sources, is also described.

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用于电子显微镜相关电子光子光谱的电子驱动光子源

摘要 由于电子能量损失光谱和阴极发光光谱等光谱工具，电子显微镜中的电子束是光学近场的有效探针。如今，我们可以通过应用空间分辨衍射和时间分辨光谱技术来获取有关纳米光子系统的大量信息。此外，与金属材料和光栅相互作用的移动电子表现为相干辐射源。快速穿过金属纳米结构的电子以电子集体激发的形式诱导极化密度波，即所谓的等离子体极化子。传播的等离子体激元波通常对辐射没有贡献；然而，它们会从自然和工程缺陷中产生衍射并引起辐射。此外，由于跃迁辐射、衍射辐射和史密斯-珀塞尔辐射，电子可以发射相干光波。迄今为止，电子束的一些辐射机制已被用于设计可调辐射源，特别是在最先进的激光技术不易获得的那些能量范围内，例如太赫兹机制。在这里，我们回顾了设计相干电子驱动光子源的各种方法。特别是，我们介绍了理论和纳米制造技术，并讨论了设计和实现电子驱动光子源的可能性，用于在超宽带光谱范围内按需辐射光束整形，从而能够实现超快的少光子源。我们还讨论了我们最近从精确制造的纳米结构中产生结构光的尝试。