Integrated Cherenkov radiation emitter eliminating the electron velocity threshold


Cherenkov radiation1,2,3,4 has played a key role in the discovery of some fundamental particles and physical phenomena, including anti-protons5, J particles6 and neutrino oscillations4. The electron energy (velocity) threshold required to generate Cherenkov radiation in a natural medium is greater than hundreds of keV (refs 3,4). Although various approaches have been adopted, high-energy electrons (tens of keV)7 are still required to generate Cherenkov radiation experimentally. Here, we demonstrate, in hyperbolic metamaterial, that the electron velocity threshold for Cherenkov radiation can be eliminated. Based on this threshold-less Cherenkov radiation, the first integrated free-electron light source has been realized. Cherenkov radiation covering λ0 ≈ 500–900 nm is obtained with an electron energy of only 0.25–1.4 keV, which is two to three orders of magnitude lower than in previous reports3,7,8,9. This work provides a way to achieve threshold-less Cherenkov radiation, opens up the possibility of exploring high-performance integrated free-electron light sources and optoelectronic devices, and offers a platform to study the interaction of flying electrons with nanostructures on chip.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: The integrated CR emitter.
Figure 2: Measured optical output of the integrated CR emitter.
Figure 3: Calculation of CR in HMM.


  1. 1

    Cherenkov, P. Visible emission of clean liquids by action of gamma radiation. Dokl. Akad. Nauk 2, 451 (1934).

  2. 2

    Landau, L. D. & Lifshitz, E. M. Electrodynamics of Continuous Media 2nd edn (Pergamon, 1984).

  3. 3

    Cherenkov, P. in Nobel Lectures, Physics: 1942–62 (ed. Nobel Foundation Staff) 426–440 (Elsevier, 1964).

  4. 4

    Bolotovskii, B. M. Vavilov–Cherenkov radiation: its discovery and application. Phys. Uspekhi 52, 1099–1110 (2009).

  5. 5

    Chamberlain, O., Segrè, E., Wiegand, C. & Ypsilantis, T. Observation of antiprotons. Phys. Rev. 100, 947–950 (1955).

  6. 6

    Aubert, J. J. et al. Experimental observation of a heavy particle J. Phys. Rev. Lett. 33, 1404–1406 (1974).

  7. 7

    Adamo, G. et al. Light well: a tunable free-electron light source on a chip. Phys. Rev. Lett. 103, 113901 (2009).

  8. 8

    Smith, S. & Purcell, E. Visible light from localized surface charges moving across a grating. Phys. Rev. 92, 1069 (1953).

  9. 9

    So, J.-K., García de Abajo, F. J., MacDonald, K. F. & Zheludev, N. I. Amplification of the evanescent field of free electrons. ACS Photon. 2, 1236–1240 (2015).

  10. 10

    Stevens, T. E., Wahlstrand, J. K., Kuhl, J. & Merlin, R. Cherenkov radiation at speeds below the light threshold: phonon-assisted phase matching. Science 291, 627–630 (2001).

  11. 11

    Luo, C., Ibanescu, M., Johnson, S. G. & Joannopoulos, J. D. Cerenkov radiation in photonic crystals. Science 299, 368–371 (2003).

  12. 12

    Cook, A. M. et al. Observation of narrow-band terahertz coherent Cherenkov radiation from a cylindrical dielectric-lined waveguide. Phys. Rev. Lett. 103, 095003 (2009).

  13. 13

    Xi, S. et al. Experimental verification of reversed Cherenkov radiation in left-handed metamaterial. Phys. Rev. Lett. 103, 194801 (2009).

  14. 14

    Chen, H. & Chen, M. Flipping photons backward: reversed Cherenkov radiation. Mater. Today 14, 34–41 (2011).

  15. 15

    Ren, H., Deng, X., Zheng, Y., An, N. & Chen, X. Nonlinear Cherenkov radiation in an anomalous dispersive medium. Phys. Rev. Lett. 108, 223901 (2012).

  16. 16

    Liu, S. et al. Surface polariton Cherenkov light radiation source. Phys. Rev. Lett. 109, 153902 (2012).

  17. 17

    Ginis, V., Danckaert, J., Veretennicoff, I. & Tassin, P. Controlling Cherenkov radiation with transformation-optical metamaterials. Phys. Rev. Lett. 113, 167402 (2014).

  18. 18

    Galyamin, S. N. & Tyukhtin, A. V. Electromagnetic field of a charge traveling into an anisotropic medium. Phys. Rev. E 84, 056608 (2011).

  19. 19

    Vorobev, V. V. & Tyukhtin, A. V. Nondivergent Cherenkov radiation in a wire metamaterial. Phys. Rev. Lett. 108, 184801 (2012).

  20. 20

    Fernandes, D. E., Maslovski, S. I. & Silveirinha, M. G. Cherenkov emission in a nanowire material. Phys. Rev. B 85, 155107 (2012).

  21. 21

    So, J. et al. Cherenkov radiation in metallic metamaterials. Appl. Phys. Lett. 97, 151107 (2010).

  22. 22

    Galyamin, S. N., Kapshtan, D. Y. & Tyukhtin, A. V. Electromagnetic field of a charge moving in a cold magnetized plasma. Phys. Rev. E 87, 013109 (2013).

  23. 23

    Adamo, G. et al. Electron-beam-driven collective-mode metamaterial light source. Phys. Rev. Lett. 109, 217401 (2012).

  24. 24

    Poddubny, A., Iorsh, I., Belov, P. & Kivshar, Y. Hyperbolic metamaterials. Nat. Photon. 7, 948–957 (2013).

  25. 25

    Yang, X., Yao, J., Rho, J., Yin, X. & Zhang, X. Experimental realization of three-dimensional indefinite cavities at the nanoscale with anomalous scaling laws. Nat. Photon. 6, 450–454 (2012).

  26. 26

    García de Abajo, F. J. Optical excitations in electron microscopy. Rev. Mod. Phys. 82, 209–275 (2010).

  27. 27

    Sihvola, A. Electromagnetic Mixing Formulas and Applications (Institution of Engineering and Technology, 1999).

  28. 28

    Palik, E. D. Handbook of Optical Constants of Solids (Academic, 1985).

  29. 29

    Garate, E., Cook, R., Heim, P., Layman, R. & Walsh, J. Čerenkov maser operation at lower-mm wavelengths. J. Appl. Phys. 58, 627–632 (1985).

  30. 30

    Felch, K. L., Busby, K. O., Layman, R. W., Kapilow, D. & Walsh, J. E. Cerenkov radiation in dielectric-lined waveguides. Appl. Phys. Lett. 38, 601–603 (1981).

Download references


The authors thank J. Feng, G. Bai and X. Li in Beijing Vacuum Electronics Research Institute for help in testing the chip. The authors also thank Y. Zhang and A. Lambert for polishing the English. This work was supported by the National Basic Research Programs of China (973 Program) under contract no. 2013CBA01704 and the National Natural Science Foundation of China (NSFC-61575104 and 61621064).

Author information




F.L. proposed the idea of CR in HMM and directed L.X., Y.Y. and M.W. for the research work. F.L. and L.X. performed the theoretical study. F.L., L.X., Y.Y. and M.W. performed the numerical simulations. F.L., L.X. and Y.H. designed the device and experiment. F.L., L.X., Y.Y. and M.W. fabricated the samples and carried out the measurements. F.L., L.X., Y.Y., M.W., K.C., X.F., W.Z. and Y.H. discussed the results. F.L., L.X. and Y.H. wrote the manuscript, which was revised by all authors. F.L. and Y.H. led the overall direction of the project.

Corresponding authors

Correspondence to Fang Liu or Yidong Huang.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary information

Supplementary information (PDF 1300 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Liu, F., Xiao, L., Ye, Y. et al. Integrated Cherenkov radiation emitter eliminating the electron velocity threshold. Nature Photon 11, 289–292 (2017).

Download citation

Further reading