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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.

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

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

    Google Scholar 

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

    Google Scholar 

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

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

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

  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).

    Article  Google Scholar 

  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).

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

  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).

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

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

    Article  Google Scholar 

  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).

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

  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).

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

  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).

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

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

    Book  Google Scholar 

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

    Google Scholar 

  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).

    Article  ADS  Google Scholar 

  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).

    Article  ADS  Google Scholar 

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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).

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Authors and Affiliations



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.

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Correspondence to Fang Liu or Yidong Huang.

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The authors declare no competing financial interests.

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

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