Optical Excitations with Electron Beams: Challenges and Opportunities.
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TLDR
In this paper, it was shown that the excitation probability by a single electron is independent of its wave function, apart from a classical average over the transverse beam density profile, whereas the probability for two or more modulated electrons depends on their relative spatial arrangement, thus reflecting the quantum nature of their interactions.Abstract:
Free electron beams such as those employed in electron microscopes have evolved into powerful tools to investigate photonic nanostructures with an unrivaled combination of spatial and spectral precision through the analysis of electron energy losses and cathodoluminescence light emission. In combination with ultrafast optics, the emerging field of ultrafast electron microscopy utilizes synchronized femtosecond electron and light pulses that are aimed at the sampled structures, holding the promise to bring simultaneous sub-Angstrom--sub-fs--sub-meV space-time-energy resolution to the study of material and optical-field dynamics. In addition, these advances enable the manipulation of the wave function of individual free electrons in unprecedented ways, opening sound prospects to probe and control quantum excitations at the nanoscale. Here, we provide an overview of photonics research based on free electrons, supplemented by original theoretical insights, and discussion of challenges and opportunities. In particular, we show that the excitation probability by a single electron is independent of its wave function, apart from a classical average over the transverse beam density profile, whereas the probability for two or more modulated electrons depends on their relative spatial arrangement, thus reflecting the quantum nature of their interactions. We derive first-principles analytical expressions that embody these results and have general validity for arbitrarily shaped electrons and any type of electron-sample interaction. We conclude with perspectives on various exciting directions for disruptive approaches to non-invasive spectroscopy and microscopy, the possibility of sampling the nonlinear optical response at the nanoscale, the manipulation of the density matrices associated with free electrons and optical sample modes, and applications in optical modulation of electron beams.read more
Citations
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Free-Electron Shaping Using Quantum Light
TL;DR: In this paper, the authors show that for fixed optical intensity, phase-squeezed light can be used to accelerate the compression of free electron pulses, while amplitude squeezing produces ultrashort double-pulse profiles.
References
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meV resolution in laser-assisted energy-filtered transmission electron microscopy
Enrico Pomarico,I. Madan,Gabriele Berruto,Giovanni Maria Vanacore,Kangpeng Wang,Ido Kaminer,F. J. García de Abajo,Fabrizio Carbone +7 more
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TL;DR: A perspective view on how a two-dimensional (2D) Dirac fermion-based microscope can be realistically implemented and operated, using graphene as a vacuum chamber for ballistic electrons, is provided.
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Probing Higher Order Surface Plasmon Modes on Individual Truncated Tetrahedral Gold Nanoparticle Using Cathodoluminescence Imaging and Spectroscopy Combined with FDTD Simulations
TL;DR: In this article, the spatial maps of localized surface plasmon resonances associated with photon emission in a truncated tetrahedral gold nanoparticle on a silicon substrate were reported.
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Design of an electron microscope phase plate using a focused continuous-wave laser
TL;DR: The relativistic quantum theory of the phase shift caused by the laser-electron interaction is presented, resonant cavities for enhancing the laser intensity are studied and applications in biology, soft-materials science and atomic and molecular physics are discussed.
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Creating and Steering Highly Directional Electron Beams in Graphene.
TL;DR: This work combines negative refraction and Klein collimation at a parabolic pn junction to create highly collimated, nondispersive electron beams in pseudorelativistic Dirac materials such as graphene or topological insulator surfaces.