Optical nano-imaging of gate-tunable graphene plasmons (original) (raw)

Nature volume 487, pages 77–81 (2012) Cite this article

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Abstract

The ability to manipulate optical fields and the energy flow of light is central to modern information and communication technologies, as well as quantum information processing schemes. However, because photons do not possess charge, a way of controlling them efficiently by electrical means has so far proved elusive. A promising way to achieve electric control of light could be through plasmon polaritons—coupled excitations of photons and charge carriers—in graphene1,2,3,4,5. In this two-dimensional sheet of carbon atoms6, it is expected that plasmon polaritons and their associated optical fields can readily be tuned electrically by varying the graphene carrier density. Although evidence of optical graphene plasmon resonances has recently been obtained spectroscopically7,8, no experiments so far have directly resolved propagating plasmons in real space. Here we launch and detect propagating optical plasmons in tapered graphene nanostructures using near-field scattering microscopy with infrared excitation light9,10,11. We provide real-space images of plasmon fields, and find that the extracted plasmon wavelength is very short—more than 40 times smaller than the wavelength of illumination. We exploit this strong optical field confinement to turn a graphene nanostructure into a tunable resonant plasmonic cavity with extremely small mode volume. The cavity resonance is controlled in situ by gating the graphene, and in particular, complete switching on and off of the plasmon modes is demonstrated, thus paving the way towards graphene-based optical transistors. This successful alliance between nanoelectronics and nano-optics enables the development of active subwavelength-scale optics and a plethora of nano-optoelectronic devices and functionalities, such as tunable metamaterials12, nanoscale optical processing, and strongly enhanced light–matter interactions for quantum devices13 and biosensing applications.

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Figure 1: Imaging propagating and localized graphene plasmons by scattering-type SNOM.

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Figure 2: Controlling the plasmon wavelength over a wide range.

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Figure 3: Comparison of theoretical model with experimental results.

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Figure 4: Plasmonic switching and active control of the plasmon wavelength by electrical gating.

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Acknowledgements

We thank L. Novotny, N. van Hulst, R. Quidant and P. Jarillo-Herrero for discussions. This work was supported in part by the Fundacicio Cellex Barcelona, the Spanish MICINN (MAT2010-14885 and Consolider NanoLight.es), the European FP7 projects FP7-HEALTH-F5-2009-241818-NANOANTENNA, FP7-ICT- 2009-4-248909-LIMA and FP7-ICT-2009-4-248855-N4E, the ERC Starting grant no. 258461 (TERATOMO), and the ERC Career integration grant GRANOP.

Author information

Author notes

  1. Jianing Chen, Michela Badioli, Pablo Alonso-González, Sukosin Thongrattanasiri and Florian Huth: These authors contributed equally to this work.

Authors and Affiliations

  1. CIC nanoGUNE Consolider, 20018 Donostia-San Sebastián, Spain ,
    Jianing Chen, Pablo Alonso-González, Florian Huth & Rainer Hillenbrand
  2. Centro de Fisica de Materiales (CSIC-UPV/EHU) and Donostia International Physics Center (DIPC), 20018 Donostia-San Sebastián, Spain ,
    Jianing Chen
  3. ICFO-Institut de Ciéncies Fotoniques, Mediterranean Technology Park, 08860 Castelldefels, Barcelona, Spain ,
    Michela Badioli, Johann Osmond, Marko Spasenović & Frank H. L. Koppens
  4. IQFR-CSIC, Serrano 119, 28006 Madrid, Spain ,
    Sukosin Thongrattanasiri & F. Javier García de Abajo
  5. Neaspec GmbH, 82152 Martinsried, Munich, Germany ,
    Florian Huth
  6. Graphenea SA, 20018 Donostia-San Sebastián, Spain ,
    Alba Centeno, Amaia Pesquera & Amaia Zurutuza Elorza
  7. CNM-IMB-CSIC–Campus UAB, 08193 Bellaterra, Barcelona, Spain ,
    Philippe Godignon
  8. GREMAN, UMR 7347, Université de Tours/CNRS, 37071 Tours Cedex 2, France ,
    Nicolas Camara
  9. IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain ,
    Rainer Hillenbrand

Authors

  1. Jianing Chen
  2. Michela Badioli
  3. Pablo Alonso-González
  4. Sukosin Thongrattanasiri
  5. Florian Huth
  6. Johann Osmond
  7. Marko Spasenović
  8. Alba Centeno
  9. Amaia Pesquera
  10. Philippe Godignon
  11. Amaia Zurutuza Elorza
  12. Nicolas Camara
  13. F. Javier García de Abajo
  14. Rainer Hillenbrand
  15. Frank H. L. Koppens

Contributions

J.C., P.A.-G., F.H., F.H.L.K. and R.H. carried out the near-field imaging experiments and participated in data analysis. M.S. participated in data analysis. S.T. and F.J.G.d.A. contributed to the interpretation of the data and developed analytical and computational theoretical tools. N.C., P.G., A.C., A.P. and A.Z.E. provided materials. M.B. and J.O. fabricated the devices. J.G.d.A., R.H. and F.H.L.K. wrote the manuscript.

Corresponding authors

Correspondence toF. Javier García de Abajo, Rainer Hillenbrand or Frank H. L. Koppens.

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Competing interests

R.H. is co-founder of Neaspec GmbH, a company producing scattering-type scanning near-field optical microscope systems, such as the one used in this study. All other authors declare no competing financial interests.

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Chen, J., Badioli, M., Alonso-González, P. et al. Optical nano-imaging of gate-tunable graphene plasmons.Nature 487, 77–81 (2012). https://doi.org/10.1038/nature11254

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Editorial Summary

Voltage-controlled graphene plasmonics

Plasmonic devices, which exploit surface plasmons (electromagnetic waves that propagate along the surface of metals) offer the possibility of controlling and guiding light at subwavelength scales. All eyes are on graphene — atom-thick layers of carbon — as a promising platform for plasmonic applications because it can strongly interact with light and host surface plasmons in the infrared range. Two independent groups reporting in this issue of Nature show that plasmons can be directly launched in graphene, and observed with near-field optical microscopy. Moreover, the wavelengths and amplitudes of the plasmons can be tuned by a gate voltage, a promising capability for the development of on-chip graphene photonics for use in applications including telecommunications and information processing.