Free-electron beams are versatile probes of microscopic structure and composition1,2, and have revolutionized atomic-scale imaging in several fields, from solid-state physics to structural biology3. Over the past decade, the manipulation and interaction of electrons with optical fields have enabled considerable progress in imaging methods4, near-field electron acceleration5,6, and four-dimensional microscopy techniques with high temporal and spatial resolution7. However, electron beams typically couple only weakly to optical excitations, and emerging applications in electron control and sensing8,9,10,11 require large enhancements using tailored fields and interactions. Here we couple a free-electron beam to a travelling-wave resonant cavity mode. The enhanced interaction with the optical whispering-gallery modes of dielectric microresonators induces a strong phase modulation on co-propagating electrons, which leads to a spectral broadening of 700 electronvolts, corresponding to the absorption and emission of hundreds of photons. By mapping the near-field interaction with ultrashort electron pulses in space and time, we trace the lifetime of the the microresonator following a femtosecond excitation and observe the spectral response of the cavity. The natural matching of free electrons to these quintessential optical modes could enable the application of integrated photonics technology in electron microscopy, with broad implications for attosecond structuring, probing quantum emitters and possible electron–light entanglement.
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The data supporting the findings of this study are available within the paper and at the Open Science Framework repository at https://osf.io/5da8g/?view_only=779f3a157219431bb51e48bc3fd47f47. Source data for Figs. 1–3 are provided with the paper.
Oh, S. H., Kauffmann, Y., Scheu, C., Kaplan, W. D. & Rühle, M. Ordered liquid aluminum at the interface with sapphire. Science 310, 661–663 (2005).
Kimoto, K. et al. Element-selective imaging of atomic columns in a crystal using STEM and EELS. Nature 450, 702–704 (2007).
Glaeser, R. M. How good can cryo-EM become? Nat. Methods 13, 28–32 (2016).
Barwick, B., Flannigan, D. J. & Zewail, A. H. Photon-induced near-field electron microscopy. Nature 462, 902–906 (2009).
Peralta, E. A. et al. Demonstration of electron acceleration in a laser-driven dielectric microstructure. Nature 503, 91–94 (2013).
Breuer, J. & Hommelhoff, P. Laser-based acceleration of nonrelativistic electrons at a dielectric structure. Phys. Rev. Lett. 111, 134803 (2013).
Carbone, F., Kwon, O.-H. & Zewail, A. H. Dynamics of chemical bonding mapped by energy-resolved 4D electron microscopy. Science 325, 181–184 (2009).
Cai, W., Sainidou, R., Xu, J., Polman, A. & García de Abajo, F. J. Efficient generation of propagating plasmons by electron beams. Nano Lett. 9, 1176–1181 (2009).
Kfir, O. Entanglements of electrons and cavity photons in the strong-coupling regime. Phys. Rev. Lett. 123, 103602 (2019).
Di Giulio, V., Kociak, M. & García de Abajo, F. J. Probing quantum optical excitations with fast electrons. Optica 6, 1524–1534 (2019).
Schwartz, O. et al. Laser phase plate for transmission electron microscopy. Nat. Methods 16, 1016–1020 (2019).
García de Abajo, F. J. Optical excitations in electron microscopy. Rev. Mod. Phys. 82, 209–275 (2010).
Talebi, N. Interaction of electron beams with optical nanostructures and metamaterials: from coherent photon sources towards shaping the wave function. J. Opt. 19, 103001 (2017).
García de Abajo, F. J. & Kociak, M. Probing the photonic local density of states with electron energy loss spectroscopy. Phys. Rev. Lett. 100, 106804 (2008).
Nelayah, J. et al. Mapping surface plasmons on a single metallic nanoparticle. Nat. Phys. 3, 348–353 (2007).
Talebi, N. et al. Excitation of mesoscopic plasmonic tapers by relativistic electrons: phase matching versus eigenmode resonances. ACS Nano 9, 7641–7648 (2015).
Hörl, A. et al. Tomographic imaging of the photonic environment of plasmonic nanoparticles. Nat. Commun. 8, 37 (2017).
Bosman, M. et al. Surface plasmon damping quantified with an electron nanoprobe. Sci. Rep. 3, 1312 (2013).
García de Abajo, F. J. & Kociak, M. Electron energy-gain spectroscopy. New J. Phys. 10, 073035 (2008).
Pomarico, E. et al. meV resolution in laser-assisted energy-filtered transmission electron microscopy. ACS Photonics 5, 759–764 (2018).
Das, P. et al. Stimulated electron energy loss and gain in an electron microscope without a pulsed electron gun. Ultramicroscopy 203, 44–51 (2019).
Asenjo-Garcia, A. & García de Abajo, F. J. Plasmon electron energy-gain spectroscopy. New J. Phys. 15, 103021 (2013).
Wang, K. et al. Coherent interaction between free electrons and a photonic cavity. Nature https://doi.org/10.1038/s41586-020-2321-x (2020).
Feist, A. et al. Quantum coherent optical phase modulation in an ultrafast transmission electron microscope. Nature 521, 200–203 (2015).
Madan, I. et al. Holographic imaging of electromagnetic fields via electron-light quantum interference. Sci. Adv. 5, eaav8358 (2019).
Vanacore, G. M. et al. Ultrafast generation and control of an electron vortex beam via chiral plasmonic near fields. Nat. Mater. 18, 573–579 (2019).
Priebe, K. E. et al. Attosecond electron pulse trains and quantum state reconstruction in ultrafast transmission electron microscopy. Nat. Photon. 11, 793–797 (2017).
Morimoto, Y. & Baum, P. Diffraction and microscopy with attosecond electron pulse trains. Nat. Phys. 14, 252–256 (2018).
Kozák, M., Schönenberger, N. & Hommelhoff, P. Ponderomotive generation and detection of attosecond free-electron pulse trains. Phys. Rev. Lett. 120, 103203 (2018).
Park, S. T., Lin, M. & Zewail, A. H. Photon-induced near-field electron microscopy (PINEM): theoretical and experimental. New J. Phys. 12, 123028 (2010).
Constant, E. et al. Optimizing high harmonic generation in absorbing gases: model and experiment. Phys. Rev. Lett. 82, 1668–1671 (1999).
Breuer, J., McNeur, J. & Hommelhoff, P. Dielectric laser acceleration of electrons in the vicinity of single and double grating structures—theory and simulations. J. Phys. B 47, 234004 (2014).
Kozák, M. et al. Acceleration of sub-relativistic electrons with an evanescent optical wave at a planar interface. Opt. Express 25, 19195–19204 (2017).
Dahan, R. et al. Observation of the stimulated quantum Cherenkov effect. Preprint at https://arxiv.org/abs/1909.00757 (2019).
Aspelmeyer, M., Kippenberg, T. J. & Marquardt, F. Cavity optomechanics. Rev. Mod. Phys. 86, 1391–1452 (2014).
Brasch, V. et al. Photonic chip-based optical frequency comb using soliton Cherenkov radiation. Science 351, 357–360 (2016).
Vollmer, F. & Arnold, S. Whispering-gallery-mode biosensing: label-free detection down to single molecules. Nat. Methods 5, 591–596 (2008).
Arnold, S., Khoshsima, M., Teraoka, I., Holler, S. & Vollmer, F. Shift of whispering-gallery modes in microspheres by protein adsorption. Opt. Lett. 28, 272–274 (2003).
Aoki, T. et al. Observation of strong coupling between one atom and a monolithic microresonator. Nature 443, 671–674 (2006).
Shomroni, I. et al. All-optical routing of single photons by a one-atom switch controlled by a single photon. Science 345, 903–906 (2014).
García de Abajo, F. J., Asenjo-Garcia, A. & Kociak, M. Multiphoton absorption and emission by interaction of swift electrons with evanescent light fields. Nano Lett. 10, 1859–1863 (2010).
Liu, J. et al. Ultralow-power chip-based soliton microcombs for photonic integration. Optica 5, 1347 (2018).
Bechler, O. et al. A passive photon–atom qubit swap operation. Nat. Phys. 14, 996–1000 (2018).
He, L., Özdemir, Ş. K., Zhu, J., Kim, W. & Yang, L. Detecting single viruses and nanoparticles using whispering gallery microlasers. Nat. Nanotechnol. 6, 428–432 (2011).
Feist, A. et al. Ultrafast transmission electron microscopy using a laser-driven field emitter: femtosecond resolution with a high coherence electron beam. Ultramicroscopy 176, 63–73 (2017).
Polyanskiy, M. N. Refractive Index Database http://refractiveindex.info (2015).
Balac, S. WGMode: a Matlab toolbox for whispering gallery modes volume computation in spherical optical micro-resonators. Comput. Phys. Commun. 243, 121–134 (2019).
García de Abajo, F. J. Multiple excitation of confined graphene plasmons by single free electrons. ACS Nano 7, 11409–11419 (2013).
Yang, Y. et al. Maximal spontaneous photon emission and energy loss from free electrons. Nat. Phys. 14, 894–899 (2018); correction 14, 967 (2018).
Hörl, A., Trügler, A. & Hohenester, U. Tomography of particle plasmon fields from electron energy loss spectroscopy. Phys. Rev. Lett. 111, 076801 (2013).
Boyd, R. W. Nonlinear Optics (Academic Press, 2003).
Hansen, J. E. Spherical Near-field Antenna Measurements (IET, 1988).
Balac, S. & Féron, P. Whispering Gallery Modes Volume Computation in Optical Micro-Spheres. Report 01279396 (HAL, 2014); https://hal.archives-ouvertes.fr/hal-01279396.
Vanacore, G. M. et al. Attosecond coherent control of free-electron wave functions using semi-infinite light fields. Nat. Commun. 9, 2694 (2018); correction 10, 1069 (2019).
We acknowledge the joint effort of the UTEM team in Göttingen and especially the support of M. Möller, J. H. Gaida, T. Danz and T. Domröse. We thank J. Liu for productive discussions. O.K. gratefully acknowledges funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement number 752533. T.R.H. acknowledges the support of a postdoctoral fellowship from the Alexander von Humboldt Foundation and its sponsor, the German Federal Ministry for Education and Research. This work was funded by the Deutsche Forschungsgemeinschaft (DFG) through the Collaborative Research Center ‘Atomic Scale Control of Energy Conversion’ (DFG-SFB 1073, project A05) and the Priority Program ‘Quantum Dynamics in Tailored Intense Fields’ (DFG-SPP 1840).
The authors declare no competing interests.
Peer review information Nature thanks Nahid Talebi and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Kfir, O., Lourenço-Martins, H., Storeck, G. et al. Controlling free electrons with optical whispering-gallery modes. Nature 582, 46–49 (2020). https://doi.org/10.1038/s41586-020-2320-y
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