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  • Open Access

High-Energy Subcycle Electron Emission Driven by Spatiotemporally Confined THz Fields

Jianwei Ying1, Lufei Liu2, Lingbin Zheng1, Dace Su1, Xie He1, Jingui Ma1, Hongwen Xuan2,3,*, and Dongfang Zhang1,†

  • *Contact author: xuanhw@aircas.ac.cn
  • †Contact author: dongfangzhang@sjtu.edu.cn
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Phys. Rev. X 15, 021095 – Published 18 June, 2025

DOI: https://doi.org/10.1103/wczq-1jv3

Abstract

Tip-based structures offer a pathway to strong-field, optical-driven field emission, holding the potential for generating high-brightness ultrashort electron sources. While direct optical-field-driven electron emission and acceleration within the single optical subcycle provides a straightforward solution for ultrafast electron generation, achieving precise control over the emission process to generate high-quality electron beams suitable for practical applications remains challenging. Here, we present THz-driven subcycle electron field emission in a ridged waveguide cavity, achieving the first practical high-energy femtosecond field-emission source. This ridged cavity is engineered to spatially and temporally confine the electric field, effectively minimizing dispersion and suppressing field leakage. Through carrier-envelope phase control of the THz field, we achieve subcycle field emission, generating, for the first time, isolated electron bunches with a 940-fs (FWHM) duration. Using dual 24  μJ (2×24  μJ) of THz energy, we achieve a peak field strength of approximately 23  GV/m, accelerating electrons to a record energy of 46 keV with a charge of 2 pC per bunch, thereby enabling single-shot imaging. The high-field strength suppresses emittance blowup due to space-charge effects, ensuring excellent beam quality. The generated electron pulse exhibits high stability. As an initial application, we investigate transient electric-field dynamics in real time and space using time-resolved schlieren radiography with this field-emission electron source. These proof-of-principle results signify a critical advancement in developing compact, high-performance electron sources for user-oriented applications.

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Popular Summary

Generating ultrashort, high-quality electron beams is important for technologies like ultrafast electron diffraction and free-electron lasers. Traditionally, creating these beams with high precision has been difficult due to limited control over how electrons are emitted and accelerated. In this study, we solve this problem by demonstrating a new way to control electron emission using terahertz (THz) light waves. We present the first practical electron source driven directly by an optical field, using a specially designed waveguide to achieve precise, subcycle control of the emission process.

Our setup uses a ridged waveguide cavity that concentrates THz fields into a very small region while preventing energy loss. By carefully tuning the phase of the THz wave (known as carrier-envelope phase control), we generate electron pulses lasting just 940 fs (FWHM). The system produces strong electric fields—up to 23 GV/m—that accelerate electrons to energies of 46 keV. This is nearly an order of magnitude better than previous attempts. We also achieve a record beam charge of 2 pC per pulse, making single-shot imaging possible. The electron pulses are stable and well timed with the optical field, reducing jitter and improving accuracy. We used the electron pulses to visualize fast-changing electric fields using a method called time-resolved schlieren radiography.

Looking ahead, this technology could lead to compact, high-performance tools for studying matter at extremely short timescales, such as tabletop electron microscopes or radiation sources.

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References (44)

  1. G. Herink, D. R. Solli, M. Gulde, and C. Ropers, Field-driven photoemission from nanostructures quenches the quiver motion, Nature (London) 483, 190 (2012).
  2. C. Tóth, G. Farkas, and K. L. Vodopyanov, Laser-induced electron emission from an Au surface irradiated by single picosecond pulses at λ=2.94  μm. The intermediate region between multiphoton and tunneling effects, Appl. Phys. B 53, 221 (1991).
  3. A. Apolonski, P. Dombi, G. G. Paulus, M. Kakehata, R. Holzwarth, T. Udem, C. Lemell, K. Torizuka, J. Burgdörfer, T. W. Hänsch, and F. Krausz, Observation of light-phase-sensitive photoemission from a metal, Phys. Rev. Lett. 92, 073902 (2004).
  4. H. Y. Kim, M. Garg, S. Mandal, L. Seiffert, T. Fennel, and E. Goulielmakis, Attosecond field emission, Nature (London) 613, 662 (2023).
  5. F. Krausz and M. Ivanov, Attosecond physics, Rev. Mod. Phys. 81, 163 (2009).
  6. P. B. Corkum and F. Krausz, Attosecond science, Nat. Phys. 3, 381 (2007).
  7. P. Dienstbier, L. Seiffert, T. Paschen, A. Liehl, A. Leitenstorfer, T. Fennel, and P. Hommelhoff, Tracing attosecond electron emission from a nanometric metal tip, Nature (London) 616, 702 (2023).
  8. R. Bormann, M. Gulde, A. Weismann, S. V. Yalunin, and C. Ropers, Tip-enhanced strong-field photoemission, Phys. Rev. Lett. 105, 147601 (2010).
  9. W. P. Putnam, R. G. Hobbs, P. D. Keathley, K. K. Berggren, and F. X. Kärtner, Optical-field-controlled photoemission from plasmonic nanoparticles, Nat. Phys. 13, 335 (2016).
  10. G. Tóth, G. Polónyi, and J. Hebling, Tilted pulse front pumping techniques for efficient terahertz pulse generation, Light Sci. Appl. 12, 256 (2023).
  11. L. Wimmer, G. Herink, D. R. Solli, S. V. Yalunin, K. E. Echternkamp, and C. Ropers, Terahertz control of nanotip photoemission, Nat. Phys. 10, 432 (2014).
  12. S. Li and R. R. Jones, High-energy electron emission from metallic nano-tips driven by intense single-cycle terahertz pulses, Nat. Commun. 7, 13405 (2016).
  13. D. Matte, N. Chamanara, L. Gingras, Laurent P. Rene de Cotret, T. L. Britt, B. J. Siwick, and D. G. Cooke, Extreme lightwave electron field emission from a nanotip, Phys. Rev. Res. 3, 013137 (2021).
  14. S. L. Lange, N. K. Noori, T. M. B. Kristensen, K. Steenberg, and P. U. Jepsen, Ultrafast THz-driven electron emission from metal metasurfaces, J. Appl. Phys. 128, 070901 (2020).
  15. S. Li, A. Sharma, Z. Márton, P. S. Nugraha, C. Lombosi, Z. Ollmann, I. Márton, P. Dombi, J. Hebling, and J. A. Fülöp, Subcycle surface electron emission driven by strong-field terahertz waveforms, Nat. Commun. 14, 6596 (2023).
  16. D. Zhang, A. Fallahi, M. Hemmer, H. Ye, M. Fakhari, Y. Hua, H. Cankaya, A.-L. Calendron, L. E. Zapata, N. H. Matlis, and F. X. Kärtner, Femtosecond phase control in high-field terahertz-driven ultrafast electron sources, Optica 6, 872 (2019).
  17. X.-Q. Yu, Y.-S. Zeng, L.-W. Song, D.-Y. Kong, S.-B. Hao, J.-Y. Gui, X.-J. Yang, Y. Xu, X.-J. Wu, Y.-X. Leng, Y. Tian, and R.-X. Li, Megaelectronvolt electron acceleration driven by terahertz surface waves, Nat. Photonics 17, 957 (2023).
  18. J. Ying, X. He, D. Su, L. Zheng, T. Kroh, T. Rohwer, M. Fakhari, G. H. Kassier, J. Ma, P. Yuan, N. H. Matlis, F. X. Kärtner, and D. Zhang, High gradient terahertz-driven ultrafast photogun, Nat. Photonics 18, 758 (2024).
  19. H. Tang, L. Zhao, P. Zhu, X. Zou, J. Qi, Y. Cheng, J. Qiu, X. Hu, W. Song, D. Xiang, and J. Zhang, Stable and scalable multistage terahertz-driven particle accelerator, Phys. Rev. Lett. 127, 074801 (2021).
  20. E. Curry, S. Fabbri, J. Maxson, P. Musumeci, and A. Gover, Meter-scale terahertz-driven acceleration of a relativistic beam, Phys. Rev. Lett. 120, 094801 (2018).
  21. M. T. Hibberd, A. L. Healy, D. S. Lake, V. Georgiadis, E. J. H. Smith, O. J. Finlay, T. H. Pacey, J. K. Jones, Y. Saveliev, D. A. Walsh, E. W. Snedden, R. B. Appleby, G. Burt, D. M. Graham, and S. P. Jamison, Acceleration of relativistic beams using laser-generated terahertz pulses, Nat. Photonics 14, 755 (2020).
  22. H. Xu, L. Yan, Y. Du, W. Huang, Q. Tian, R. Li, Y. Liang, S. Gu, J. Shi, and C. Tang, Cascaded high-gradient terahertz-driven acceleration of relativistic electron beams, Nat. Photonics 15, 426 (2021).
  23. D. Zhang, M. Fakhari, H. Cankaya, A.-L. Calendron, N. H. Matlis, and F. X. Kärtner, Cascaded multicycle terahertz-driven ultrafast electron acceleration and manipulation, Phys. Rev. X 10, 011067 (2020).
  24. C. Kealhofer, W. Schneider, D. Ehberger, A. Ryabov, F. Krausz, and P. Baum, All-optical control and metrology of electron pulses, Science 352, 429 (2016).
  25. E. C. Snively, M. A. K. Othman, M. Kozina, B. K. Ofori-Okai, S. P. Weathersby, S. Park, X. Shen, X. J. Wang, M. C. Hoffmann, R. K. Li, and E. A. Nanni, Femtosecond compression dynamics and timing jitter suppression in a THz-driven electron bunch compressor, Phys. Rev. Lett. 124, 054801 (2020).
  26. L. Zhao, H. Tang, C. Lu, T. Jiang, P. Zhu, L. Hu, W. Song, H. Wang, J. Qiu, C. Jing, S. Antipov, D. Xiang, and J. Zhang, Femtosecond relativistic electron beam with reduced timing jitter from THz driven beam compression, Phys. Rev. Lett. 124, 054802 (2020).
  27. J. W. Wang and G. A. Loew, RF breakdown studies in copper electron linac structures, in Proceedings of the 1989 IEEE Particle Accelerator Conference, Accelerator Science and Technology, Chicago, IL (IEEE, New York, NY, 1989), pp. 1137–1139, 10.1109/PAC.1989.73374.
  28. S. Manz et al., Mapping atomic motions with ultrabright electrons: Towards fundamental limits in space-time resolution, Faraday Discuss. 177, 467 (2015).
  29. A. A. Ischenko, P. M. Weber, and R. J. D. Miller, Capturing chemistry in action with electrons: Realization of atomically resolved reaction dynamics, Chem. Rev. 117, 11066 (2017).
  30. X. Yang, J. Li, M. Fedurin, V. Smaluk, L. Yu, L. Wu, W. Wan, Y. Zhu, and T. Shaftan, A novel nondestructive diagnostic method for mega-electron-volt ultrafast electron diffraction, Sci. Rep. 9, 17223 (2019).
  31. D. Zhang, A. Fallahi, M. Hemmer, X. Wu, M. Fakhari, Y. Hua, H. Cankaya, A.-L. Calendron, L. E. Zapata, N. H. Matlis, and F. X. Kärtner, Segmented terahertz electron accelerator and manipulator (STEAM), Nat. Photonics 12, 336 (2018).
  32. W. Ronny Huang, A. Fallahi, X. Wu, H. Cankaya, A.-L. Calendron, K. Ravi, D. Zhang, E. A. Nanni, K.-H. Hong, and F. X. Kärtner, Terahertz-driven, all-optical electron gun, Optica 3, 1209 (2016).
  33. K. Hasegawa and H. Hayano, Design of a low emittance electron gun with GV/m high field, Nucl. Instrum. Methods Phys. Res., Sect. A 554, 59 (2005).
  34. R. J. Bakker, A. Adelmann, A. Anghel, M. Dehler, R. Ganter, S. C. Leemann, K. Li, M. Pedrozzi, J. Y. Raguin, L. Rivkin, V. Schlott, F. Wei, A. Wrulich, and P. K. Scherrer, Ultra high brightness accelerator design, in Proceedings of FEL, Berlin, Germany (JACoW, Geneva, Switzerland, 2006), pp. 214–217, https://accelconf.web.cern.ch/f06/PAPERS/MOPPH072.PDF.
  35. J. Hebling, G. Almasi, I. Kozma, and J. Kuhl, Velocity matching by pulse front tilting for large area THz-pulse generation, Opt. Express 10, 1161 (2002).
  36. Supplemental Material at http://link.aps.org/supplemental/10.1103/wczq-1jv3 for details on the design of the ridged waveguide and expanded cascade structures, characterization of the field emission process, additional simulations of the effects of CEP and work function on electron dynamics, and further improvements in beam quality through multidimensional electron manipulation.
  37. C. Bruns, P. Leuchtmann, and R. Vahldieck, Analysis and simulation of a 1-18-GHz broadband double-ridged horn antenna, IEEE Transactions on Electromagnetic Compatibility 45, 55 (2003).
  38. A. Fallahi, M. Fakhari, A. Yahaghi, M. Arrieta, and F. X. Kärtner, Short electron bunch generation using single-cycle ultrafast electron guns, Phys. Rev. Accel. Beams 19, 081302 (2016).
  39. R. H. Fowler and L. Nordheim, Electron emission in intense electric fields, Proc. R. Soc. A 119, 173 (1928).
  40. D. J. Park, B. Piglosiewicz, S. Schmidt, H. Kollmann, M. Mascheck, and C. Lienau, Strong field acceleration and steering of ultrafast electron pulses from a sharp metallic nanotip, Phys. Rev. Lett. 109, 244803 (2012).
  41. B. Piglosiewicz, S. Schmidt, D. J. Park, J. Vogelsang, P. Groß, C. Manzoni, P. Farinello, G. Cerullo, and C. Lienau, Carrier-envelope phase effects on the strong-field photoemission of electrons from metallic nanostructures, Nat. Photonics 8, 37 (2013).
  42. J. Houard, L. Arnoldi, A. Ayoub, A. Hideur, and A. Vella, Nanotip response to monocycle terahertz pulses, Appl. Phys. Lett. 117, 151105 (2020).
  43. L. Chen, R. Li, J. Chen, P. Zhu, F. Liu, J. Cao, Z. Sheng, and J. Zhang, Mapping transient electric fields with picosecond electron bunches, Proc. Natl. Acad. Sci. U.S.A. 112, 14479 (2015).
  44. J. Ying et al., Dataset for ‘High-Energy Sub-cycle Electron Emission Driven by Spatio-temporally Confined THz Fields’. figshare 10.6084/m9.figshare.29209109 (2025).

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Phys. Rev. X 15, 021095– Published 18 June, 2025
  • Received 4 November 2024
  • Accepted 3 June 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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