Free-Electrons Coupled to High-Q Microresonators
The inelastic interaction of fast electrons with confined optical fields in transmission electron microscopy provide a wide range of nano-optical properties. Despite the rapid experimental progress recently made regarding the interaction of electrons with coherent light (e.g. by laser illumination), only a limited number of studies have addressed the coupling of non-classical (quantum optical) light states with (free) electrons. In our experiments we aim to study the coupling of fast electrons to optical micro-resonator modes of the whispering gallery type (WGM). These modes are well known for their exceptional long life-times (high Q-factors), possible enabling the photon mediated entanglement between subsequent electrons in a beam. In a first attempt we have used a microfibre tip as resonator geometry and a broad range of WGM resonances induced by fast electrons within a TEM could be observed.