Controlling free electrons with optical whispering-gallery modes

Kfir, Ofer; Lourenço-Martins, Hugo; Storeck, Gero; Sivis, Murat; Harvey, Tyler R.; Kippenberg, Tobias J.; Feist, Armin; Ropers, Claus

doi:10.1038/s41586-020-2320-y

Cited by 169 publications

(118 citation statements)

References 51 publications

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“…If the electron beam is coherent in space, then it should also be possible to advance electron holography or picodiffraction (44,45) to highly dynamical setting at frequencies approaching those of light, and atomic subcycle diffraction may reveal the complex real-space motions of valence electron densities that are the atomistic origin of the macroscopic optical properties of materials (16,17). Quantum optics with free-electron wave functions (23,(46)(47)(48) and general three-body interactions of light, electrons, and matter (49) may profit from the extremely narrow spectroscopic bandwidth that is offered by a continuous laser wave (30). In cryogenic electron microscopy, the orientation of biomolecules might be identified by their optical dipole response, and a modulated electron beam in particle colliders might reveal the physics of the collisions as a function of time.…”

Section: Discussionmentioning

confidence: 99%

Attosecond metrology in a continuous-beam transmission electron microscope

et al. 2020

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Electron microscopy can visualize the structure of complex materials with atomic and subatomic resolution, but investigations of reaction dynamics and light-matter interaction call for time resolution as well, ideally on a level below the oscillation period of light. Here, we report the use of the optical cycles of a continuous-wave laser to bunch the electron beam inside a transmission electron microscope into electron pulses that are shorter than half a cycle of light. The pulses arrive at the target at almost the full average brightness of the electron source and in synchrony to the optical cycles, providing attosecond time resolution of spectroscopic features. The necessary modifications are simple and can turn almost any electron microscope into an attosecond instrument that may be useful for visualizing the inner workings of light-matter interaction on the basis of the atoms and the cycles of light.

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Section: Discussionmentioning

confidence: 99%

Attosecond metrology in a continuous-beam transmission electron microscope

et al. 2020

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“…The measurement of asymmetric intensity changes for our nanostructured array at frequencies approaching those of light therefore indicates that electromagnetic potentials are of equal significance in highly dynamical settings as in static ones and demonstrates that terahertz-compressed electron pulses can provide a valuable technology for studying the Aharonov-Bohm effect at 10 9 times higher frequencies than accessible before (32,33). We touch here an extreme limit of quantum-coherent light-electron interaction, the topic of many recent reports (34,35). In contrast to studies with near-infrared light (34,35), where photon-order sidebands appear in the spectrum, the electron wave function in our experiment is much smaller than a wavelength of the radiation in free space and its temporal coherence is much smaller than a cycle period.…”

Section: Discussionmentioning

confidence: 62%

“…We touch here an extreme limit of quantum-coherent light-electron interaction, the topic of many recent reports (34,35). In contrast to studies with near-infrared light (34,35), where photon-order sidebands appear in the spectrum, the electron wave function in our experiment is much smaller than a wavelength of the radiation in free space and its temporal coherence is much smaller than a cycle period. In other words, the electrons seem like point particles with respect to the optical waveform, like in all other electron-terahertz interactions reported so far.…”

Section: Discussionmentioning

confidence: 83%

Ultrafast electron diffraction from nanophotonic waveforms via dynamical Aharonov-Bohm phases

et al. 2020

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Electron interferometry via phase-contrast microscopy, holography, or picodiffraction can provide a direct visualization of the static electric and magnetic fields inside or around a material at subatomic precision, but understanding the electromagnetic origin of light-matter interaction requires time resolution as well. Here, we demonstrate that pump-probe electron diffraction with all-optically compressed electron pulses can capture dynamic electromagnetic potentials in a nanophotonic material with sub-light-cycle time resolution via centrosymmetry-violating Bragg spot dynamics. The origin of this effect is a sizable quantum mechanical phase shift that the electron de Broglie wave obtains from the oscillating electromagnetic potentials within less than 1 fs. Coherent electron imaging and scattering can therefore reveal the electromagnetic foundations of light-matter interaction on the level of the cycles of light.

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“…The basics of this interaction are succinctly captured in the Kapitza-Dirac effect introduced a long time ago [3] and recently experimentally detected [4,5] and further generalized to include arbitrary light shapes [6]. To explore the possibilities of retrieving the sample dynamics using electron microscopes, an in-depth understanding of the interaction between ultrafast electron wave packet, intense ultrafast laser pulse, and nanostructure is crucial [7][8][9][10]. Recent efforts toward retrieving the dynamics is captured in the so-called field of photoinduced near-field electron microscopy [11].…”

Section: Introductionmentioning

confidence: 99%

Electron-driven photon sources for correlative electron-photon spectroscopy with electron microscopes

et al. 2020

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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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Controlling free electrons with optical whispering-gallery modes

Cited by 169 publications

References 51 publications

Attosecond metrology in a continuous-beam transmission electron microscope

Attosecond metrology in a continuous-beam transmission electron microscope

Ultrafast electron diffraction from nanophotonic waveforms via dynamical Aharonov-Bohm phases

Electron-driven photon sources for correlative electron-photon spectroscopy with electron microscopes

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