Integrated photonics enables continuous-beam electron phase modulation

Jan Wilke Henke, Arslan Sajid Raja, Armin Feist, Guanhao Huang, Germaine Arend, Yujia Yang, F. Jasmin Kappert, Rui Ning Wang, Marcel Möller, Jiahe Pan, Junqiu Liu, Ofer Kfir, Claus Ropers*, Tobias J. Kippenberg*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Integrated photonics facilitates extensive control over fundamental light–matter interactions in manifold quantum systems including atoms1, trapped ions2,3, quantum dots4 and defect centres5. Ultrafast electron microscopy has recently made free-electron beams the subject of laser-based quantum manipulation and characterization6–11, enabling the observation of free-electron quantum walks12–14, attosecond electron pulses10,15–17 and holographic electromagnetic imaging18. Chip-based photonics19,20 promises unique applications in nanoscale quantum control and sensing but remains to be realized in electron microscopy. Here we merge integrated photonics with electron microscopy, demonstrating coherent phase modulation of a continuous electron beam using a silicon nitride microresonator. The high-finesse (Q0 ≈ 106) cavity enhancement and a waveguide designed for phase matching lead to efficient electron–light scattering at extremely low, continuous-wave optical powers. Specifically, we fully deplete the initial electron state at a cavity-coupled power of only 5.35 microwatts and generate >500 electron energy sidebands for several milliwatts. Moreover, we probe unidirectional intracavity fields with microelectronvolt resolution in electron-energy-gain spectroscopy21. The fibre-coupled photonic structures feature single-optical-mode electron–light interaction with full control over the input and output light. This approach establishes a versatile and highly efficient framework for enhanced electron beam control in the context of laser phase plates22, beam modulators and continuous-wave attosecond pulse trains23, resonantly enhanced spectroscopy24–26 and dielectric laser acceleration19,20,27. Our work introduces a universal platform for exploring free-electron quantum optics28–31, with potential future developments in strong coupling, local quantum probing and electron–photon entanglement.

Original languageEnglish
Pages (from-to)653-658
Number of pages6
Issue number7890
StatePublished - 23 Dec 2021
Externally publishedYes


FundersFunder number
EU H2020 research and innovation programme101033593
Air Force Office of Scientific ResearchFA9550-19-1-0250
Horizon 2020 Framework Programme101017720
Deutsche Forschungsgemeinschaft432680300/SFB 1456, C01
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung182103, 185870, 176563


    Dive into the research topics of 'Integrated photonics enables continuous-beam electron phase modulation'. Together they form a unique fingerprint.

    Cite this